AMERICAN BUILDINGS CO /DE/
SC 14D1, 1999-04-13
PREFABRICATED METAL BUILDINGS & COMPONENTS
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<PAGE>   1
 
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                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                            ------------------------
 
                                 SCHEDULE 14D-1
                             TENDER OFFER STATEMENT
                      PURSUANT TO SECTION 14(D)(1) OF THE
                        SECURITIES EXCHANGE ACT OF 1934
 
                   UNDER THE SECURITIES EXCHANGE ACT OF 1934
 
                           AMERICAN BUILDINGS COMPANY
                           (NAME OF SUBJECT COMPANY)
 
                            ------------------------
 
                ABCO ACQUISITION CORP., ABCO HOLDINGS CORP. AND
                                ONEX CORPORATION
                                    (BIDDER)
 
                     COMMON STOCK, PAR VALUE $.01 PER SHARE
                         (TITLE OF CLASS OF SECURITIES)
 
                            ------------------------
 
                                   024757106
                     (CUSIP NUMBER OF CLASS OF SECURITIES)
 
                                 MARK L. HILSON
                                NIGEL S. WRIGHT
                        C/O ONEX INVESTMENT CORPORATION
                                712 FIFTH AVENUE
                                   40TH FLOOR
                            NEW YORK, NEW YORK 10019
           (NAME, ADDRESS AND TELEPHONE NUMBER OF PERSONS AUTHORIZED
          TO RECEIVE NOTICES AND COMMUNICATIONS ON BEHALF OF BIDDERS)
 
                                    COPY TO:
                            JOEL I. GREENBERG, ESQ.
                             LYNN TOBY FISHER, ESQ.
                  KAYE, SCHOLER, FIERMAN, HAYS & HANDLER, LLP
                                425 PARK AVENUE
                               NEW YORK, NY 10022
                                 (212) 836-8000
                            ------------------------
 
<TABLE>
<CAPTION>
        TRANSACTION VALUATION*                 AMOUNT OF FILING FEE*
        ----------------------                 ---------------------
<S>                                    <C>
             $207,809,640                            $41,561.93
</TABLE>
 
- ---------------
*  Value derived by multiplying 5,772,490 (number of shares of common stock
   outstanding on a fully diluted basis less shares of common stock beneficially
   owned by Purchaser and its affiliates) by $36 (the purchase price per share
   offered by the bidder). Amount of filing fee, calculated in accordance with
   Rule 0-11, equals 1/50th of one percent of the value of the transaction.
 
[ ]  Check box if any part of the fee is offset as provided by Rule 0-11(a)(2)
and identify the filing with which the offsetting fee was previously paid.
Identify the previous filing by registration statement number, or the Form or
Schedule and the date of its filing.
 
<TABLE>
<S>                                    <C>
     Amount Previously Paid: N/A           Form or Registration No.: N/A
          Filing Party: N/A                       Date Filed: N/A
</TABLE>
 
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<PAGE>   2
 
     This Tender Offer Statement on Schedule 14D-1 (the "Schedule 14D-1")
relates to a tender offer by ABCO Acquisition Corp., a Delaware corporation
("Purchaser"), a wholly-owned subsidiary of ABCO Holdings Corp., a Delaware
corporation ("Parent") and an indirect wholly-owned subsidiary of Onex
Corporation, an Ontario corporation ("Onex"), to purchase all outstanding shares
of Common Stock, par value $.01 per share, of American Buildings Company, a
Delaware corporation (the "Company"), for a purchase price of $36 per share, net
to the seller in cash, without interest thereon, upon the terms and subject to
the conditions set forth in the Offer to Purchase dated April 13, 1999 (the
"Offer to Purchase") and in the related Letter of Transmittal (the "Letter of
Transmittal" and together with the Offer to Purchase, as the same may be amended
or supplemented from time to time, the "Offer"), and is intended to satisfy the
disclosure and filing requirements of Section 14(d) of the Securities Exchange
Act of 1934, as amended. Copies of the Offer to Purchase and the related Letter
of Transmittal are filed with this Schedule 14D-1 as Exhibits (a)(1) and (a)(2)
hereto, respectively.
 
ITEM 1.  SECURITIES AND SUBJECT COMPANY.
 
     (a) The name of the subject company is American Buildings Company, a
Delaware corporation, which has its principal executive offices at 1150 State
Docks Road, Eufaula, Alabama 36027.
 
     (b) The title of the securities which are the subject of the Offer is the
Company's Common Stock, par value $.01 per share (the "Shares"), and the Offer
is for all outstanding Shares at a price of $36 per Share, net to the seller in
cash, without interest thereon. The information set forth in the "Introduction"
to the Offer to Purchase is incorporated herein by reference.
 
     (c) The information set forth in Section 6 of the Offer to Purchase is
incorporated herein by reference.
 
ITEM 2.  IDENTITY AND BACKGROUND.
 
     (a)-(d) and (g). This Schedule 14D-1 is being filed jointly by Purchaser,
Parent and Onex. The information set forth in the "Introduction" to the Offer to
Purchase, in Section 9 of the Offer to Purchase and in Schedule I to the Offer
to Purchase is incorporated herein by reference.
 
     (e) and (f) None.
 
ITEM 3.  PAST CONTACTS, TRANSACTIONS OR NEGOTIATIONS WITH THE SUBJECT COMPANY.
 
     (a)-(b) The information set forth in the "Introduction" to the Offer to
Purchase, in Sections 9, 11 and 13 of the Offer to Purchase and in Schedule I to
the Offer to Purchase is incorporated herein by reference.
 
ITEM 4.  SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.
 
     (a)-(b) The information set forth in Section 10 of the Offer to Purchase is
incorporated herein by reference.
 
     (c) Not applicable.
 
ITEM 5.  PURPOSE OF THE TENDER OFFER AND PLANS OR PROPOSALS OF THE BIDDER.
 
     (a)-(e) The information set forth in the "Introduction" to the Offer to
Purchase and in Sections 9 and 12 of the Offer to Purchase is incorporated
herein by reference.
 
     (f) and (g) The information set forth in Sections 7 and 12 of the Offer to
Purchase is incorporated herein by reference.
 
ITEM 6.  INTEREST IN SECURITIES OF THE SUBJECT COMPANY.
 
     (a) and (b) The information set forth in the "Introduction" to the Offer to
Purchase and in Sections 9 and 11 of the Offer to Purchase is incorporated
herein by reference.
 
                                        2
<PAGE>   3
 
ITEM 7.  CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT
         TO THE SUBJECT COMPANY'S SECURITIES.
 
     The information set forth in the "Introduction" to the Offer to Purchase in
Sections 9, 11 and 13 of the Offer to Purchase and in Schedule I to the Offer to
Purchase is incorporated herein by reference.
 
ITEM 8.  PERSONS RETAINED, EMPLOYED OR TO BE COMPENSATED.
 
     The information set forth in Section 17 of the Offer to Purchase is
incorporated herein by reference.
 
ITEM 9.  FINANCIAL STATEMENTS OF CERTAIN BIDDERS.
 
     Not applicable.
 
ITEM 10.  ADDITIONAL INFORMATION.
 
     (a) None.
 
     (b) and (c) The information set forth in Section 16 of the Offer to
Purchase is incorporated herein by reference.
 
     (d) Not applicable.
 
     (e) Not applicable.
 
     (f) The information set forth in the Offer to Purchase, the Letter of
Transmittal, the Press Release dated April 8, 1999, the Agreement and Plan of
Merger, dated as of April 7, 1999, among Parent, Purchaser and the Company, the
undertaking of Onex to the Company dated April 7, 1999 and the Confidentiality
Agreement, dated as of March 8, 1999, between the Company and Onex, copies of
which are attached hereto as Exhibits (a)(1), (a)(2), (a)(7), (c)(1), (c)(2) and
(c)(3), respectively, is incorporated herein by reference.
 
ITEM 11.  MATERIAL TO BE FILED AS EXHIBITS.
 
(a)(1)  Offer to Purchase.
 
(a)(2)  Letter of Transmittal.
 
(a)(3)  Notice of Guaranteed Delivery.
 
(a)(4)  Letter to Brokers, Dealers, Banks, Trust Companies and Other Nominees.
 
(a)(5)  Letter to Clients for use by Brokers, Dealers, Banks, Trust Companies
        and Other Nominees.
 
(a)(6)  Guidelines for Certification of Taxpayer Identification Number on
        Substitute Form W-9.
 
(a)(7)  Text of Press Release dated April 8, 1999.
 
(b)     None.
 
(c)(1)  Agreement and Plan of Merger, dated as of April 7, 1999, among Parent,
        Purchaser and the Company.*
 
(c)(2)  Undertaking of Onex Corporation to the Company dated April 7, 1999.
 
(c)(3)  Confidentiality Agreement, dated as of March 8, 1999, between the
        Company and Onex.
 
(d)     None.
 
(e)     Not applicable.
 
(f)     None.
 
- ---------------
 
* Incorporated by reference to American Buildings Company's Current Report on
 Form 8-K dated April 7, 1999 and filed with the Securities and Exchange
 Commission on April 8, 1999.
                                        3
<PAGE>   4
 
                                   SIGNATURE
 
     After due inquiry and to the best of my knowledge and belief, I certify
that the information set forth in this statement is true, complete and correct.
 
April 13, 1999
                                          ABCO Acquisition Corp.
 
                                          By /s/ MARK L. HILSON
 
                                            ------------------------------------
                                            Mark L. Hilson, President
 
                                          ABCO Holdings Corp.
 
                                          By /s/ MARK L. HILSON
 
                                            ------------------------------------
                                            Mark L. Hilson, President
 
                                          Onex Corporation
 
                                          By /s/ MARK L. HILSON
 
                                            ------------------------------------
                                            Mark L. Hilson, Vice President
 
                                        4
<PAGE>   5
 
                                 EXHIBIT INDEX
 
<TABLE>
<CAPTION>
EXHIBIT                                                                 SEQUENTIALLY
NUMBER                           DESCRIPTION                           NUMBERED PAGES
- -------                          -----------                           --------------
<S>      <C>                                                           <C>
(a)(1)   Offer to Purchase.
(a)(2)   Letter of Transmittal.
(a)(3)   Notice of Guaranteed Delivery.
(a)(4)   Letter to Brokers, Dealers, Banks, Trust Companies and Other
         Nominees.
(a)(5)   Letter to Clients for use by Brokers, Dealers, Banks, Trust
         Companies and Other Nominees.
(a)(6)   Guidelines for Certification of Taxpayer Identification
         Number on Substitute Form W-9.
(a)(7)   Text of Press Release dated April 8, 1999.
(b)      None.
(c)(1)   Agreement and Plan of Merger, dated as of April 7, 1999,
         among Parent, Purchaser and the Company.*
(c)(2)   Undertaking of Onex to the Company dated April 7, 1999.
(c)(3)   Confidentiality Agreement, dated as of March 8, 1999,
         between the Company and Onex.
(d)      None.
(e)      Not applicable.
(f)      None.
</TABLE>
 
- ---------------
 
* Incorporated by reference to American Buildings Company's Current Report on
  Form 8-K dated April 7, 1999 and filed with the Securities and Exchange
  Commission on April 8, 1999.

<PAGE>   1
 
                           OFFER TO PURCHASE FOR CASH
                     ALL OUTSTANDING SHARES OF COMMON STOCK
 
                                       OF
 
                           AMERICAN BUILDINGS COMPANY
                                       AT
 
                               $36 NET PER SHARE
 
                                       BY
 
                             ABCO ACQUISITION CORP.
                     AN INDIRECT WHOLLY-OWNED SUBSIDIARY OF
                            [ONEX CORPORATION LOGO]
 
  THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY
          TIME, ON MONDAY, MAY 10, 1999, UNLESS THE OFFER IS EXTENDED.
 
     THE OFFER IS BEING MADE PURSUANT TO AN AGREEMENT AND PLAN OF MERGER AMONG
ABCO HOLDINGS CORP., ABCO ACQUISITION CORP. AND AMERICAN BUILDINGS COMPANY. THE
BOARD OF DIRECTORS OF THE COMPANY HAS UNANIMOUSLY (WITH ONE DIRECTOR NOT
PRESENT) APPROVED THE MERGER AGREEMENT, THE OFFER AND THE MERGER DESCRIBED
HEREIN AND DEEMED THEM TO BE ADVISABLE, HAS DETERMINED THAT THE TERMS OF THE
OFFER AND THE MERGER ARE FAIR TO, AND IN THE BEST INTERESTS OF, THE STOCKHOLDERS
OF THE COMPANY AND RECOMMENDS THAT THE STOCKHOLDERS OF THE COMPANY ACCEPT THE
OFFER AND TENDER THEIR SHARES PURSUANT TO THE OFFER.
 
     THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS, (1) THERE BEING VALIDLY
TENDERED AND NOT WITHDRAWN PRIOR TO THE EXPIRATION OF THE OFFER THAT NUMBER OF
SHARES OF COMMON STOCK OF THE COMPANY WHICH, TOGETHER WITH THE SHARES THEN OWNED
BY ABCO ACQUISITION CORP. AND ITS AFFILIATES, WOULD CONSTITUTE A MAJORITY OF THE
OUTSTANDING SHARES ON A FULLY-DILUTED BASIS AND (2) THE EXPIRATION OR
TERMINATION OF ANY APPLICABLE WAITING PERIOD UNDER THE HART-SCOTT-RODINO
ANTITRUST IMPROVEMENTS ACT OF 1976, AS AMENDED. SEE SECTIONS 15 AND 16. THE
OFFER IS NOT CONDITIONED ON THE AVAILABILITY OF FINANCING.
 
     Warburg Dillon Read LLC, financial advisor to the Company, has delivered to
the Board of Directors of the Company its written opinion to the effect that, as
of April 7, 1999, the $36 in cash to be received by the holders of Shares in the
Offer and the Merger described below is fair to such holders from a financial
point of view. The full text of the written opinion of Warburg Dillon Read LLC
containing the assumptions made, the matters considered and the scope of the
review undertaken in rendering such opinion as well as the limitations of such
opinion is included with the Company's solicitation/recommendation statement on
Schedule 14D-9, which is being mailed to stockholders of the Company
concurrently herewith. Stockholders of the Company are urged to read the full
text of such opinion in conjunction with the Offer.
                            ------------------------
<PAGE>   2
 
                                   IMPORTANT
 
     Any stockholder desiring to tender all or a portion of such stockholder's
Shares should either (i) complete and sign the Letter of Transmittal (or a
facsimile thereof) in accordance with the instructions in the Letter of
Transmittal, have such stockholder's signature thereon guaranteed if required by
Instruction 1 to the Letter of Transmittal, and mail or deliver the Letter of
Transmittal together with the certificate(s) representing tendered Shares and
all other required documents to American Stock Transfer & Trust Company, which
is acting as the Depositary (in such capacity, the "Depositary"), or tender such
Shares pursuant to the procedure for book-entry transfer set forth in Section 3
or (ii) request such stockholder's broker, dealer, commercial bank, trust
company or other nominee to effect the transaction for such stockholder.
Stockholders having Shares registered in the name of a broker, dealer,
commercial bank, trust company or other nominee must contact such person if they
desire to tender their Shares. Any stockholder who desires to tender Shares and
whose certificates representing such Shares are not immediately available, or
who cannot comply with the procedures for book-entry transfer on a timely basis,
may tender such Shares pursuant to the guaranteed delivery procedure set forth
in Section 3.
 
     Questions and requests for assistance may be directed to the Information
Agent at its address and telephone numbers set forth on the back cover.
Additional copies of this Offer to Purchase, the Letter of Transmittal, the
Notice of Guaranteed Delivery and other related materials may be obtained from
the Information Agent or from brokers, dealers, commercial banks and trust
companies.
                            ------------------------
 
                    The Information Agent for the Offer is:
 
                               MORROW & CO., INC.
 
April 13, 1999
 
                                        2
<PAGE>   3
 
                               TABLE OF CONTENTS
 
<TABLE>
<CAPTION>
                                                                   PAGE
                                                                   ----
<S>  <C>                                                           <C>
INTRODUCTION.....................................................    4
 1.  Terms of the Offer..........................................    7
 2.  Acceptance for Payment and Payment for Shares...............    8
 3.  Procedure for Tendering Shares..............................    9
 4.  Withdrawal Rights...........................................   12
 5.  Certain United States Federal Income Tax Consequences.......   13
 6.  Price Range of Shares.......................................   14
 7.  Effect of the Offer on the Market for the Shares, Inclusion
     in the Nasdaq National Market and Exchange Act
     Registration................................................   14
 8.  Certain Information Concerning the Company..................   15
 9.  Certain Information Concerning Parent, Purchaser and Onex...   19
10.  Source and Amount of Funds..................................   20
11.  Background of the Offer; Past Contacts, Transactions or
     Negotiations with the Company...............................   21
12.  Purpose of the Offer and the Merger; Short Form Merger;
     Plans for the Company; Appraisal Rights; Going Private
     Transactions................................................   23
13.  Merger Agreement; Certain Other Agreements..................   25
14.  Dividends and Distributions.................................   34
15.  Certain Conditions of the Offer.............................   34
16.  Certain Regulatory and Legal Matters........................   36
17.  Fees and Expenses...........................................   37
18.  Miscellaneous...............................................   38
SCHEDULE I: Information Concerning Directors and Executive
  Officers of Parent, Purchaser and Onex and Purchases of Company
  Shares by Onex and its Affiliates..............................  I-1
</TABLE>
 
                                        3
<PAGE>   4
 
To the Holders of Common Stock of American Buildings Company:
 
                                  INTRODUCTION
 
     ABCO Acquisition Corp., a Delaware corporation ("Purchaser"), a
wholly-owned subsidiary of ABCO Holdings Corp., a Delaware corporation
("Parent") and an indirect wholly-owned subsidiary of Onex Corporation, an
Ontario corporation ("Onex"), hereby offers to purchase all the outstanding
shares of common stock, par value $.01 per share (the "Shares"), of American
Buildings Company, a Delaware corporation (the "Company"), at a purchase price
of $36 per Share (the "Offer Price"), net to the seller in cash, without
interest thereon, upon the terms and subject to the conditions set forth in this
Offer to Purchase and in the related Letter of Transmittal (which together, as
the same may be amended or supplemented from time to time, constitute the
"Offer"). Parent and Purchaser were organized by Onex, a Canadian public company
which focuses its investments in companies which are leaders in their
industries. See Section 9.
 
     Tendering stockholders will not be obligated to pay brokerage fees or
commissions or, subject to Instruction 6 of the Letter of Transmittal, stock
transfer taxes on the purchase of Shares by Purchaser pursuant to the Offer.
However, any tendering stockholder or other payee who fails to complete and sign
the Substitute Form W-9 that is included in the Letter of Transmittal may be
subject to a required backup federal income tax withholding of 31% of the gross
proceeds payable to such stockholder or other payee pursuant to the Offer. See
Section 2. Purchaser will pay all charges and expenses of Morrow & Co., Inc.,
which is acting as Information Agent (the "Information Agent"), and American
Stock Transfer & Trust Company, which is acting as Depositary (the
"Depositary"), incurred in connection with the Offer. See Section 17.
 
     The Offer is being made pursuant to an Agreement and Plan of Merger, dated
as of April 7, 1999 (the "Merger Agreement"), by and among Parent, Purchaser and
the Company. The Merger Agreement provides, among other things, that as soon as
practicable after the purchase of Shares pursuant to the Offer and the
satisfaction or waiver of the other conditions set forth in the Merger
Agreement, and in accordance with the relevant provisions of the Delaware
General Corporation Law (the "DGCL"), Purchaser will be merged with and into the
Company (the "Merger"). See Section 13. Following consummation of the Merger,
the Company will continue as the surviving corporation (the "Surviving
Corporation") and will be a wholly-owned subsidiary of Parent and an indirect
wholly-owned subsidiary of Onex. At the effective time of the Merger (the
"Effective Time"), by virtue of the Merger and without any action on the part of
the holders thereof, each Share issued and outstanding immediately prior to the
Effective Time (other than Shares owned by Parent, Purchaser, the Company or any
of the Company's subsidiaries, which shall be canceled, and other than
Dissenting Shares (as defined in the Merger Agreement)) will be converted into
and represent the right to receive, without interest, the price paid for each
Share in the Offer (the "Merger Consideration"). The Merger Agreement is more
fully described in Section 13. Certain United States federal income tax
consequences of the sale of Shares pursuant to the Offer and the Merger, as the
case may be, are described in Section 5.
 
     THE BOARD OF DIRECTORS OF THE COMPANY HAS UNANIMOUSLY (WITH ONE DIRECTOR
NOT PRESENT) APPROVED THE MERGER AGREEMENT, THE OFFER AND THE MERGER AND DEEMED
THEM TO BE ADVISABLE, HAS DETERMINED THAT THE TERMS OF THE OFFER AND THE MERGER
ARE FAIR TO, AND IN THE BEST INTERESTS OF, THE STOCKHOLDERS OF THE COMPANY AND
RECOMMENDS THAT THE STOCKHOLDERS OF THE COMPANY ACCEPT THE OFFER AND TENDER
THEIR SHARES PURSUANT TO THE OFFER.
 
     The Merger Agreement provides that promptly upon the acceptance for payment
of, and payment for, Shares by Purchaser pursuant to the Offer, Purchaser shall
be entitled to designate such number of directors (rounded up to the next whole
number) on the Board of Directors of the Company (the "Board") as will give
Purchaser, subject to compliance with Section 14(f) of the Securities Exchange
Act of 1934, as amended (the "Exchange Act"), up to that percentage of the total
number of directors on the Board (giving effect to the
 
                                        4
<PAGE>   5
 
election of any additional directors described below) equal to the percentage of
then outstanding Shares so accepted for payment, together with Shares owned by
Parent or any of its affiliates, and the Company shall, at such time, cause
Purchaser's designees to be so elected by its existing Board; provided, however,
that in the event that such designees are elected to the Board, until the
Effective Time the Board must have at least two directors who were directors on
the date of the Merger Agreement and are not officers of the Company
("Independent Directors"). Following the election of Purchaser's designees and
prior to the Effective Time, any amendment or termination of the Merger
Agreement or waiver of any of the Company's rights thereunder shall require the
affirmative vote of a majority of the Independent Directors.
 
     If Purchaser acquires at least 90% of the Shares, Delaware law permits it
to effect the Merger without a stockholders' meeting and without the approval
of, or further notice to, the other Company stockholders. Purchaser intends to
cause the Merger to become effective as soon as reasonably practicable. Once the
Offer is consummated, if permitted by applicable law and regulation, and in any
event upon consummation of the Merger, Purchaser intends to cause the Company to
file applications to withdraw the Shares from listing and trading on The Nasdaq
National Market and to terminate the registration of the Shares under the
Exchange Act.
 
     The total amount of funds required by Purchaser to purchase all Shares
pursuant to the Offer and the Merger, and to pay the related fees and expenses,
is estimated to be approximately $215 million. Onex has agreed to provide, or
cause to be provided, such amount to Purchaser.
 
     The Offer does not constitute a solicitation of proxies for any meeting of
the Company's stockholders, nor does this Offer constitute a solicitation of
consents. Any such solicitation which Purchaser, Parent or Onex might make would
only be pursuant to separate proxy or consent materials, as the case may be, in
compliance with the requirements of the Exchange Act.
 
CERTAIN CONDITIONS TO THE OFFER
 
     The Offer is subject to the fulfillment of certain conditions, including
the following:
 
     THE MINIMUM CONDITION.  THE CONSUMMATION OF THE OFFER IS CONDITIONED UPON
THERE BEING VALIDLY TENDERED AND NOT WITHDRAWN PRIOR TO THE EXPIRATION OF THE
OFFER THAT NUMBER OF SHARES WHICH, TOGETHER WITH THE SHARES THEN OWNED BY
PURCHASER AND ITS AFFILIATES, WOULD CONSTITUTE A MAJORITY OF OUTSTANDING SHARES
ON A FULLY-DILUTED BASIS ON THE DATE OF PURCHASE (THE "MINIMUM CONDITION"). "On
a fully-diluted basis" means, as of the date of the purchase of Shares pursuant
to the Offer, the number of Shares outstanding, together with Shares the Company
is required to issue pursuant to outstanding and unexpired options to purchase
Shares, whether or not exercisable.
 
     The Company has informed Purchaser that, as of April 6, 1999, 5,076,180
Shares were issued and outstanding and 951,310 shares were reserved for issuance
pursuant to outstanding options to acquire Shares. Based on the foregoing, there
are 6,027,490 Shares outstanding on a fully-diluted basis. Purchaser and its
affiliates currently beneficially own 255,000 Shares. Accordingly, the Minimum
Condition would be satisfied if 2,758,746 Shares are validly tendered and not
withdrawn.
 
     The Company has informed Purchaser that, to the best knowledge of the
Company, all of its directors and executive officers currently intend to tender
pursuant to the Offer all Shares owned of record or beneficially by such
persons, other than Shares issuable upon the exercise of stock options and
Shares, if any, which, if tendered, could cause such persons to incur liability
under the provisions of Section 16(b) of the Exchange Act. The Company's
directors and executive officers currently own 181,961 Shares (excluding Shares
issuable upon exercise of options), representing approximately 3.6% of the
outstanding Shares.
 
     THE HSR CONDITION.  CONSUMMATION OF THE OFFER IS CONDITIONED UPON THE
EXPIRATION OR TERMINATION, PRIOR TO THE EXPIRATION DATE, OF THE WAITING PERIOD
UNDER THE HART-SCOTT-RODINO ANTITRUST IMPROVEMENTS ACT OF 1976, AS AMENDED, AND
THE RULES AND REGULATIONS THEREUNDER (THE "HSR ACT"), APPLICABLE TO THE
ACQUISITION OF THE SHARES PURSUANT TO THE OFFER.
                                        5
<PAGE>   6
 
     Parent intends to cause its ultimate parent to file with the Federal Trade
Commission and the Antitrust Division of the Department of Justice a Premerger
Notification and Report Form under the HSR Act with respect to the Offer. If
such filing is made on April 13, 1999, Parent anticipates that the waiting
period under the HSR Act applicable to the Offer will expire at 11:59 p.m., New
York City time, on April 28, 1999, unless extended. See Section 16.
 
     Certain other conditions to the consummation of the Offer are described in
Section 15. Purchaser expressly reserves the right, in its sole discretion, to
waive any one or more of the conditions to the Offer, except that Purchaser may
not waive the Minimum Condition without the consent of the Company. See Section
15.
 
     THIS OFFER TO PURCHASE AND THE RELATED LETTER OF TRANSMITTAL CONTAIN
IMPORTANT INFORMATION WHICH SHOULD BE READ BEFORE ANY DECISION IS MADE WITH
RESPECT TO THE OFFER.
 
                                        6
<PAGE>   7
 
                                THE TENDER OFFER
 
     1.  TERMS OF THE OFFER.  Upon the terms and subject to the conditions of
the Offer (including, if the Offer is extended or amended, the terms and
conditions of any extension or amendment), Purchaser will accept for payment and
pay for all Shares validly tendered prior to the Expiration Date and not
theretofore withdrawn in accordance with Section 4. The term "Expiration Date"
means 12:00 Midnight, New York City time, on Monday, May 10, 1999, unless
Purchaser shall have extended the period of time for which the Offer is open, in
which event the term "Expiration Date" shall mean the latest time and date at
which the Offer, as so extended by Purchaser, shall expire. UNDER NO
CIRCUMSTANCES WILL ANY INTEREST BE PAID ON THE PURCHASE PRICE FOR TENDERED
SHARES, REGARDLESS OF ANY EXTENSION OF THE OFFER OR ANY DELAY IN MAKING SUCH
PAYMENT.
 
     Subject to the terms of the Merger Agreement and the applicable rules and
regulations of the Securities and Exchange Commission (the "Commission"),
Purchaser expressly reserves the right, in its sole discretion, to waive the
Minimum Condition or any terms or other conditions of the Offer or to make any
other changes in the terms and conditions of the Offer. However, the Merger
Agreement provides that Purchaser may not, without the written consent of the
Company, (i) waive the Minimum Condition, (ii) reduce the number of Shares to be
purchased in the Offer or the Offer Price, (iii) modify or add to the conditions
described in Section 15, (iv) change the form of consideration to be paid in the
Offer, (v) except as provided in the Merger Agreement (as described in Section
13), extend the Offer or (vi) amend any other term of the Offer in a manner
adverse to the holders of Shares.
 
     Pursuant to the Merger Agreement, Purchaser has agreed to accept for
payment and pay for all Shares that have been validly tendered and not withdrawn
pursuant to the Offer as soon as practicable following expiration of the Offer,
provided that all conditions to the Offer set forth in Section 15 shall have
been satisfied or waived by Purchaser.
 
     If by 12:00 Midnight, New York City time, on Monday, May 10, 1999 (or any
other time then set as the Expiration Date), any or all of the conditions to the
Offer have not been satisfied or waived, Purchaser reserves the right (but shall
not be obligated), subject to the terms and conditions contained in the Merger
Agreement (including the limitations described above) and to the applicable
rules and regulations of the Commission, to (i) terminate the Offer and not
accept for payment or pay for any Shares and return all tendered Shares to the
tendering stockholders, (ii) waive all of the unsatisfied conditions (except the
Minimum Condition, which may not be waived without the Company's consent) and
accept for payment and pay for all Shares validly tendered prior to the
Expiration Date and not theretofore properly withdrawn, (iii) extend the Offer
in a manner permitted under the Merger Agreement and, subject to the right of
stockholders to withdraw Shares until the Expiration Date, retain the Shares
that have been tendered during the period or periods for which the Offer is
extended or (iv) delay acceptance for payment of, or payment for, the Shares,
subject to complying with applicable law, until satisfaction or waiver of the
conditions of the Offer.
 
     There can be no assurance that Purchaser will exercise its right to extend
the Offer.
 
     Subject to the applicable rules and regulations of the Commission and
subject to the limitations set forth in the Merger Agreement, Purchaser also
expressly reserves the right, at any time and from time to time, in its sole
discretion, to (i) delay payment for any Shares regardless of whether such
Shares were theretofore accepted for payment or (ii) terminate the Offer and not
accept for payment or pay for any Shares not theretofore accepted for payment or
paid for, if any of the conditions referred to in Section 15 have not been
satisfied or upon the occurrence of any of the events specified in Section 15,
and (iii) waive any condition or otherwise amend the Offer in any respect, in
each case by giving oral or written notice of such delay, termination, waiver or
amendment to the Depositary. Purchaser's right to delay payment for any Shares
or not to pay for any Shares theretofore accepted for payment is subject to the
applicable rules and regulations of the Commission, including Rule 14e-1(c) of
the Exchange Act relating to Purchaser's obligation to pay for or return
tendered Shares promptly after the termination or withdrawal of the Offer. The
rights reserved by Purchaser in this paragraph are in addition to Purchaser's
rights to terminate the Offer pursuant to Section 15.
 
                                        7
<PAGE>   8
 
     Any extension of the period during which the Offer is open, delay in
acceptance for payment or payment, or termination or amendment of the Offer,
will be followed, as promptly as practicable, by public announcement thereof,
such announcement, in the case of an extension, to be issued not later than 9:00
a.m., New York City time, on the next Business Day after the previously
scheduled Expiration Date in accordance with the public announcement
requirements of Rules 14d-4(c) and 14e-1(d) under the Exchange Act. Without
limiting the obligation of Purchaser under such rules or the manner in which
Purchaser may choose to make any public announcement, Purchaser currently
intends to make announcements by issuing a press release to the Dow Jones News
Service and making any appropriate filing with the Commission. For the purposes
of the Offer, "Business Day" means any day other than a Saturday, Sunday or
Federal holiday and consists of the time period from 12:01 a.m. through 12:00
midnight, Eastern time.
 
     If Purchaser makes a material change in the terms of the Offer or the
information concerning the Offer, or if it waives a material condition of the
Offer, Purchaser will disseminate additional tender offer materials and extend
the Offer if and to the extent required by Rules 14d-4(c), 14d-6(d) and 14e-1
under the Exchange Act. The minimum period during which a tender offer must
remain open following material changes in the terms of the Offer or information
concerning the Offer, other than a change in price or a change in percentage of
securities sought, will depend upon the facts and circumstances, including the
relative materiality of the changed terms or information. With respect to a
change in price or a change in percentage of securities sought, a minimum ten
Business Day period is generally required to allow for adequate dissemination to
stockholders and investor response. The requirement to extend the Offer will not
apply to the extent that the number of Business Days remaining between the
occurrence of the change and the then-scheduled Expiration Date equals or
exceeds the minimum extension period that would be required because of such
change.
 
     Consummation of the Offer is conditioned upon satisfaction of, among other
things, the Minimum Condition. If Purchaser waives the Minimum Condition (with
the Company's consent) during the last five Business Days during which the Offer
is open, Purchaser will be required to extend the Expiration Date so that the
Offer will remain open for at least five Business Days after the announcement of
such waiver or amendment is first published, sent or given to holders of Shares.
 
     In connection with the Offer, the Company has provided or will provide
Purchaser with the names and addresses of all record holders of Shares and
security position listings of Shares held in depositories for the purpose of
disseminating the Offer to holders of Shares. This Offer to Purchase, the
related Letter of Transmittal and other relevant materials will be mailed to
record holders of Shares whose names appear on the stockholder list and will be
furnished to brokers, dealers, commercial banks, trust companies and similar
persons whose names, or the names of whose nominees, appear on the stockholder
list or, if applicable, who are listed as participants in a clearing agency's
security position listing, for subsequent transmittal to beneficial owners of
Shares.
 
     2.  ACCEPTANCE FOR PAYMENT AND PAYMENT FOR SHARES.  Upon the terms and
subject to the conditions of the Offer (including, if the Offer is extended or
amended, the terms and conditions of any such extension or amendment), Purchaser
will accept for payment, and will pay for, all Shares validly tendered prior to
the Expiration Date and not theretofore withdrawn in accordance with Section 4
promptly after the later to occur of (a) the Expiration Date and (b) the
satisfaction or waiver of the conditions set forth in Section 15. Subject to
compliance with Rule 14e-1(c) under the Exchange Act and any other applicable
rules and regulations of the Commission and the terms of the Merger Agreement,
Purchaser expressly reserves the right to delay payment for Shares in order to
comply in whole or in part with any applicable law, including the HSR Act. See
Section 16.
 
     In all cases, payment for Shares accepted for payment pursuant to the Offer
will be made only after timely receipt by the Depositary of (i) certificates for
such Shares or timely confirmation (a "Book-Entry Confirmation") of a book-entry
transfer of such Shares into the Depositary's account at The Depository Trust
Company (the "Book-Entry Transfer Facility"), pursuant to the procedures set
forth in Section 3, (ii) a properly completed and duly executed Letter of
Transmittal (or a manually signed facsimile thereof), with all required
signature guarantees, or, in the case of a book-entry transfer, an Agent's
Message (as defined below) and (iii) any other documents required by the Letter
of Transmittal. The term "Agent's Message" means a
 
                                        8
<PAGE>   9
 
message transmitted by a Book-Entry Transfer Facility to, and received by, the
Depositary and forming a part of a Book-Entry Confirmation, which states that
such Book-Entry Transfer Facility has received an express acknowledgment from
the participant in such Book-Entry Transfer Facility tendering the Shares that
are the subject of the Book-Entry Confirmation that such participant has
received and agrees to be bound by the terms of the Letter of Transmittal and
that Purchaser may enforce such agreement against the participant.
 
     For purposes of the Offer, Purchaser will be deemed to have accepted for
payment, and thereby purchased, Shares validly tendered and not properly
withdrawn as, if and when Purchaser gives oral or written notice to the
Depositary, as agent for the tendering stockholders, of Purchaser's acceptance
of such Shares for payment. In all cases, payment for Shares purchased pursuant
to the Offer will be made by deposit of the purchase price with the Depositary,
which will act as agent for tendering stockholders for the purpose of receiving
payment from Purchaser and transmitting such payment to tendering stockholders.
Upon the deposit of funds with the Depositary for the purpose of making payments
to tendering stockholders, Purchaser's obligation to make such payment shall be
satisfied, and tendering stockholders must thereafter look solely to the
Depositary for payment of amounts owed to them by reason of the acceptance for
payment of Shares pursuant to the Offer. If, for any reason whatsoever,
acceptance for payment of any Shares tendered pursuant to the Offer is delayed,
or Purchaser is unable to accept for payment Shares tendered pursuant to the
Offer, then, without prejudice to the Purchaser's rights under this Offer to
Purchase, the Depositary may, nevertheless, on behalf of Purchaser, retain
tendered Shares, and, subject to compliance with the applicable rules and
regulations of the Commission, including Rule 14e-1(c) under the Exchange Act,
such Shares may not be withdrawn, except to the extent that the tendering
stockholders are entitled to withdrawal rights as described in Section 4.
 
     UNDER NO CIRCUMSTANCES WILL INTEREST BE PAID ON THE PURCHASE PRICE FOR THE
SHARES, REGARDLESS OF ANY EXTENSION OF THE OFFER OR ANY DELAY IN MAKING SUCH
PAYMENT.
 
     If any tendered Shares are not accepted for payment pursuant to the terms
and conditions of the Offer for any reason, or if certificates are submitted
representing more Shares than are tendered, certificates representing such
unpurchased or untendered Shares will be returned (or, in the case of Shares
delivered by book-entry transfer to the Book-Entry Transfer Facility, such
Shares will be credited to an account maintained within such Book-Entry Transfer
Facility), without expense to the tendering stockholder as promptly as
practicable after the expiration, termination or withdrawal of the Offer.
 
     If, prior to the Expiration Date, Purchaser increases the price being paid
for Shares accepted for payment pursuant to the Offer, such increased
consideration will be paid to all stockholders whose Shares are purchased
pursuant to the Offer, whether or not such Shares were tendered prior to such
increase in consideration.
 
     Purchaser reserves the right to transfer or assign, in whole or from time
to time in part, to one or more of its affiliates, the right to purchase Shares
tendered pursuant to the Offer, but any such transfer or assignment will not
relieve Purchaser of its obligations under the Offer or prejudice the rights of
tendering stockholders to receive payment for Shares validly tendered and
accepted for payment.
 
3.  PROCEDURE FOR TENDERING SHARES.
 
     Valid Tenders.  For Shares to be validly tendered pursuant to the Offer,
(i) a properly completed and duly executed Letter of Transmittal (or a manually
signed facsimile thereof), together with any required signature guarantees (or,
in the case of a book-entry transfer, an Agent's Message), and any other
documents required by the Transmittal Letter, must be received by the Depositary
at its address set forth on the back cover of this Offer to Purchase and either
certificates representing such Shares must be received by the Depositary along
with the Letter of Transmittal or such Shares must be tendered pursuant to the
procedure for book-entry transfer set forth below, and a Book-Entry Confirmation
must be received by the Depositary, in each case prior to the Expiration Date or
(ii) the guaranteed delivery procedure set forth below must be complied with. No
alternative, conditional or contingent tenders will be accepted. If Share
certificates are forwarded to the Depositary in multiple deliveries, a Letter of
Transmittal (or manually signed facsimile thereof), properly completed and duly
executed, must accompany each such delivery.
                                        9
<PAGE>   10
 
     Book-Entry Transfer.  The Depositary will establish an account with respect
to the Shares at the Book-Entry Transfer Facility for purposes of the Offer
within two Business Days after the date of this Offer to Purchase. Any financial
institution that is a participant in the Book-Entry Transfer Facility's systems
may make book-entry delivery of Shares by causing the Book-Entry Transfer
Facility to transfer such Shares into the Depositary's account at the Book-Entry
Transfer Facility in accordance with such Book-Entry Transfer Facility's
procedures for transfer. Although delivery of Shares may be effected through
book-entry at the Book-Entry Transfer Facility prior to the Expiration Date, the
Letter of Transmittal (or a manually signed facsimile thereof), properly
completed and duly executed, with any required signature guarantees, or an
Agent's Message in connection with a book-entry transfer, and any other required
documents, must, in any case, be transmitted to, and received by, the Depositary
at its address set forth on the back cover of this Offer to Purchase prior to
the Expiration Date or the guaranteed delivery procedures described below must
be complied with. DELIVERY OF DOCUMENTS TO THE BOOK-ENTRY TRANSFER FACILITY IN
ACCORDANCE WITH THE BOOK-ENTRY TRANSFER FACILITY'S PROCEDURES DOES NOT
CONSTITUTE DELIVERY TO THE DEPOSITARY.
 
     THE METHOD OF DELIVERY OF SHARES, THE LETTER OF TRANSMITTAL AND ALL OTHER
REQUIRED DOCUMENTS, INCLUDING DELIVERY THROUGH THE BOOK-ENTRY TRANSFER FACILITY,
IS AT THE ELECTION AND RISK OF THE TENDERING STOCKHOLDER. SHARES WILL BE DEEMED
DELIVERED ONLY WHEN ACTUALLY RECEIVED BY THE DEPOSITARY (INCLUDING, IN THE CASE
OF A BOOK-ENTRY TRANSFER, BY BOOK-ENTRY CONFIRMATION). IF DELIVERY IS BY MAIL,
REGISTERED MAIL WITH RETURN RECEIPT REQUESTED, PROPERLY INSURED, IS RECOMMENDED.
IN ALL CASES, SUFFICIENT TIME SHOULD BE ALLOWED TO ENSURE TIMELY DELIVERY.
 
     Signature Guarantee.  No signature guarantee is required on the Letter of
Transmittal (i) if the Letter of Transmittal is signed by the registered
holder(s) (which term, for purposes of this Section, includes any participant in
the Book-Entry Transfer Facility's systems whose name appears on a security
position listing as the owner of the Shares) of Shares tendered therewith and
such registered holder has not completed either the box entitled "Special
Delivery Instructions" or the box entitled "Special Payment Instructions" on the
Letter of Transmittal or (ii) if such Shares are tendered for the account of a
financial institution (including most commercial banks, savings and loan
associations and brokerage houses) that is a participant in the Security
Transfer Agent's Medallion Program, the New York Stock Exchange Medallion
Signature Guarantee Program or the Stock Exchange Medallion Program (each, an
"Eligible Institution" and, collectively, "Eligible Institutions"). In all other
cases, all signatures on Letters of Transmittal must be guaranteed by an
Eligible Institution. See Instructions 1 and 5 to the Letter of Transmittal.
 
     If the certificates for Shares are registered in the name of a person other
than the signer of the Letter of Transmittal, or if payment is to be made, or
certificates for Shares not tendered or not accepted for payment are to be
returned, to a person other than the registered holder of the certificates
surrendered, then the tendered certificates for such Shares must be endorsed or
accompanied by appropriate stock powers, in either case, signed exactly as the
name or names of the registered holders or owners appear on the certificates,
with the signatures on the certificates or stock powers guaranteed as described
above. See Instruction 5 to the Letter of Transmittal.
 
     Guaranteed Delivery.  If a stockholder desires to tender Shares pursuant to
the Offer and such stockholder's certificates for Shares are not immediately
available or time will not permit all required documents to reach the Depositary
prior to the Expiration Date or the procedure for book-entry transfer cannot be
completed on a timely basis, such Shares may nevertheless be tendered if all of
the following guaranteed delivery procedures are duly complied with:
 
          (i) the tender is made by or through an Eligible Institution;
 
          (ii) a properly completed and duly executed Notice of Guaranteed
     Delivery, substantially in the form provided by the Purchaser herewith, is
     received by the Depositary, as provided below, prior to the Expiration
     Date; and
 
                                       10
<PAGE>   11
 
          (iii) the certificates for all tendered Shares, in proper form for
     transfer (or a Book-Entry Confirmation), together with a properly completed
     and duly executed Letter of Transmittal (or a manually signed facsimile
     thereof), and any required signature guarantees (or, in the case of a
     book-entry transfer, an Agent's Message) and any other documents required
     by the Letter of Transmittal are received by the Depositary within three
     trading days after the date of execution of such Notice of Guaranteed
     Delivery. A "trading day" is any day on which The Nasdaq National Market
     (the "Nasdaq National Market") operated by the National Association of
     Security Dealers, Inc. (the "NASD"), is open for business.
 
     The Notice of Guaranteed Delivery may be delivered by hand or transmitted
by telegram, facsimile transmission or mail to the Depositary and must include a
guarantee by an Eligible Institution in the form set forth in the Notice of
Guaranteed Delivery.
 
     Notwithstanding any other provision hereof, payment for Shares accepted for
payment pursuant to the Offer will in all cases be made only after timely
receipt by the Depositary of (i) certificates for such Shares or a timely
Book-Entry Confirmation, (ii) a properly completed and duly executed Letter of
Transmittal (or a manually signed facsimile thereof), with all required
signature guarantees (or, in the case of a book-entry transfer, an Agent's
Message) and (iii) any other documents required by the Letter of Transmittal.
Accordingly, tendering stockholders may be paid at different times depending
upon when the Depositary actually receives certificates for Shares or Book-Entry
Confirmation with respect to Shares. Under no circumstances will interest be
paid on the purchase price to be paid by Purchaser for the Shares, regardless of
any extension of the Offer or any delay in making such payment.
 
     Determination of Validity.  All questions as to the form of documents and
the validity, eligibility (including time of receipt) and acceptance for payment
of any tender of Shares will be determined by Purchaser, in its sole discretion,
and its determination will be final and binding on all parties. Purchaser
reserves the absolute right to reject any or all tenders of any Shares that are
determined by it not to be in proper form or the acceptance of or payment for
which may, in the opinion of Purchaser, be unlawful. Purchaser also reserves the
absolute right, in its sole discretion, to waive any of the conditions of the
Offer subject to the limitations set forth in the Merger Agreement, or any
defect or irregularity in the tender of any Shares of any particular
stockholder, whether or not similar defects or irregularities are waived in the
case of other stockholders. Purchaser's interpretation of the terms and
conditions of the Offer (including the Letter of Transmittal and the
Instructions to the Letter of Transmittal) will be final and binding on all
parties. No tender of Shares will be deemed to have been validly made until all
defects and irregularities have been cured or waived. None of Purchaser, Parent,
Onex, the Depositary, the Information Agent or any other person will be under
any duty to give notification of any defects or irregularities in tenders or
incur any liability for failure to give any such notification.
 
     Appointment of Proxies.  By executing the Letter of Transmittal as set
forth above (including through delivery of an Agent's Message), a tendering
stockholder irrevocably appoints designees of Purchaser as such stockholder's
attorneys-in-fact and proxies, each with full power of substitution, in the
manner set forth in the Letter of Transmittal, to the full extent of such
stockholder's right with respect to the Shares tendered by such stockholder and
accepted for payment by Purchaser (and any and all non-cash dividends,
distributions, rights, other Shares or other securities or rights issued or
issuable in respect of such Shares on or after the date of this Offer to
Purchase (collectively, the "Distributions")). All such powers of attorney and
proxies shall be considered coupled with an interest in the tendered Shares.
Such appointment is effective only upon the acceptance for payment of the Shares
by Purchaser. Upon acceptance for payment, all prior powers of attorney and
proxies given by the stockholder with respect to such Shares or other securities
or rights will, without further action, be revoked and no subsequent proxies may
be given or written consents executed (and, if given or executed, will not be
deemed effective). The designees of Purchaser will, with respect to the Shares
and any Distributions, be empowered to exercise all voting and other rights of
such stockholder with respect to the Shares and any Distributions as they, in
their sole judgment, deem proper in respect of any annual or special meeting of
the Company's stockholders, any adjournment or postponement thereof, actions by
written consent in lieu of such meeting or otherwise. Purchaser reserves the
right to require that, in order for Shares to be deemed validly tendered,
immediately upon Purchaser's acceptance for payment of such Shares, Purchaser
                                       11
<PAGE>   12
 
must be able to exercise full voting, consent and other rights with respect to
such Shares and any Distributions, including voting at any meeting of
stockholders (whether annual or special or whether or not adjourned) or acting
by written consent without a meeting in respect of such Shares.
 
     Backup Federal Income Tax Withholding.  To prevent backup federal income
tax withholding with respect to payment for the Shares purchased pursuant to the
Offer, each tendering stockholder must provide the Depositary with his or her
correct taxpayer identification number ("TIN") and certify that such stockholder
is not subject to backup federal income tax withholding by completing the
Substitute Form W-9 included in the Letter of Transmittal. See Section 5 and
Instruction 8 of the Letter of Transmittal. If the stockholder is a nonresident
alien or foreign entity not subject to backup withholding, the stockholder must
give the Depositary a completed Form W-8 Certificate of Foreign Status prior to
receipt of any payments.
 
     A tender of Shares pursuant to any one of the procedures described above
will constitute the tendering stockholder's acceptance of the terms and
conditions of the Offer, as well as the tendering stockholder's representation
and warranty that (i) such stockholder has the full power and authority to
tender, sell, assign and transfer the tendered Shares (and any and all other
Shares or other securities issued or issuable in respect of such Shares on or
after April 7, 1999), and (ii) when the same are accepted for payment by the
Purchaser, the Purchaser will acquire good and unencumbered title thereto, free
and clear of all liens, restrictions, charges and encumbrances and not subject
to any adverse claims. Purchaser's acceptance for payment of Shares tendered
pursuant to the Offer will constitute a binding agreement between the tendering
stockholder and Purchaser upon the terms and subject to the conditions of the
Offer.
 
     4.  WITHDRAWAL RIGHTS.  Except as otherwise provided in this Section 4,
tenders of Shares made pursuant to the Offer are irrevocable. Shares tendered
pursuant to the Offer may be withdrawn at any time prior to the Expiration Date
and, unless theretofore accepted for payment by Purchaser pursuant to the Offer,
may also be withdrawn at any time after June 11, 1999. If purchase of or payment
for Shares is delayed for any reason or if Purchaser is unable to purchase or
pay for Shares for any reason, then, without prejudice to Purchaser's rights
under the Offer, tendered Shares may be retained by the Depositary on behalf of
Purchaser and such Shares may not be withdrawn except to the extent that
tendering stockholders are entitled to and duly exercise withdrawal rights as
set forth in this Section 4. Any such delay will be accompanied by an extension
of the Offer to the extent required by law.
 
     For a withdrawal to be effective, a written, telegraphic, telex or
facsimile transmission notice of withdrawal must be timely received by the
Depositary at its address set forth on the back cover of this Offer to Purchase
and must specify the name of the person who tendered the Shares to be withdrawn,
the number of Shares to be withdrawn and the name in which the certificates
representing such Shares are registered, if different from that of the person
who tendered the Shares. If certificates for Shares to be withdrawn have been
delivered or otherwise identified to the Depositary, then, prior to the physical
release of such certificates, the serial numbers shown on such certificates must
be submitted to the Depositary and, unless such Shares have been tendered for
the account of an Eligible Institution, the signatures on the notice of
withdrawal must be guaranteed by an Eligible Institution. If Shares have been
tendered pursuant to the procedure for book-entry transfer set forth in Section
3, any notice of withdrawal must also specify the name and number of the account
at the Book-Entry Transfer Facility to be credited with the withdrawn Shares and
must otherwise comply with the Book-Entry Transfer Facility's procedures.
 
     All questions as to the form and validity (including the time of receipt)
of any notice of withdrawal will be determined by Purchaser, in its sole
discretion, whose determination will be final and binding on all parties. None
of Purchaser, Parent, Onex, the Depositary, the Information Agent or any other
person will be under any duty to give notification of any defects or
irregularities in any notice of withdrawal or incur any liability for failure to
give any such notification.
 
     Withdrawals of tenders of Shares may not be rescinded, and any Shares
properly withdrawn will be deemed not validly tendered for purposes of the
Offer. However, withdrawn Shares may be retendered at any subsequent time prior
to the Expiration Date by following any of the procedures described in Section
3.
 
                                       12
<PAGE>   13
 
     5.  CERTAIN UNITED STATES FEDERAL INCOME TAX CONSEQUENCES.  The following
is a summary of the principal United States federal income tax consequences of
the Offer and the Merger to holders all of whose Shares are purchased pursuant
to the Offer or converted to cash in the Merger (including pursuant to the
exercise of appraisal rights). This summary is for general information only and
does not purport to be a complete analysis of all the potential tax effects of
the Offer and the Merger. This summary is based on current law, which is subject
to change, possibly with retroactive effect. There can be no assurance that the
Internal Revenue Service ("IRS") will not take a contrary view, and no ruling
from the IRS has been or will be sought. Legislative, judicial or administrative
changes may be forthcoming that could alter or modify the statements and
conclusions set forth herein. Any such changes or interpretations could be
retroactive and could affect the tax consequences to holders whose Shares are
purchased pursuant to the Offer. The discussion does not purport to deal with
all aspects of United States federal income taxation that may affect any
particular holder in light of such holder's individual investment circumstances,
and is not intended for certain types of holders subject to special treatment
under the United States federal income tax law (e.g., holders of Shares in whose
hands Shares are not capital assets, holders who received their Shares pursuant
to the exercise of employee stock options or otherwise as compensation,
financial institutions, broker-dealers, insurance companies, tax-exempt
organizations, non-United States persons or persons who hold their Shares as
part of a hedge, straddle, or conversion transaction).
 
     BECAUSE INDIVIDUAL CIRCUMSTANCES MAY DIFFER, EACH STOCKHOLDER SHOULD
CONSULT SUCH STOCKHOLDER'S OWN TAX ADVISOR REGARDING THE APPLICABILITY OF THE
RULES DISCUSSED BELOW TO SUCH STOCKHOLDER AND THE PARTICULAR TAX EFFECTS TO SUCH
STOCKHOLDER OF THE OFFER AND THE MERGER, INCLUDING THE APPLICATION AND EFFECT OF
STATE, LOCAL, FOREIGN AND OTHER TAX LAWS.
 
     The receipt of cash for Shares pursuant to the Offer or the Merger
(including pursuant to the exercise of appraisal rights) will be a taxable
transaction for United States federal income tax purposes, and also may be a
taxable transaction under applicable state, local, foreign and other tax laws.
In general, for United States federal income tax purposes, a holder of Shares
that receives cash pursuant to the Offer or the Merger will recognize gain or
loss equal to the difference between his or her adjusted tax basis in the Shares
sold pursuant to the Offer or converted to cash in the Merger and the amount of
cash received therefor. Gain or loss must be determined separately for each
block of Shares (i.e., Shares acquired at the same cost in a single transaction)
sold pursuant to the Offer or converted to cash in the Merger. Such gain or loss
generally will be capital gain or loss, provided the Shares are a capital asset
in the hands of a stockholder and the stockholder retains no interest in the
Company, and will be long-term capital gain or loss if, on the date of sale (or,
if applicable, the date of the Merger), the Shares were held for more than one
year. If a holder exercises such holder's appraisal rights and receives an
amount treated as interest for federal income tax purposes, such amount will be
taxed as ordinary income.
 
     Payments in connection with the Offer or the Merger may be subject to
"backup withholding" at a rate of 31%. Backup withholding generally applies if
the holder (a) fails to furnish such holder's social security number or taxpayer
identification number ("TIN"), (b) furnishes an incorrect TIN, (c) is subject to
backup withholding due to previous failures to file a federal income tax return
including reportable interest or dividend payments, or (d) under certain
circumstances, fails to provide a certified statement, signed under penalties of
perjury, that such holder is not subject to backup withholding due to previous
failures to file a federal income tax return including reportable interest or
dividend payments. Backup withholding is not an additional tax, but rather it is
an advance tax payment that is subject to refund if and to the extent that it
results in an overpayment of tax. Certain taxpayers are generally exempt from
backup withholding, including corporations and financial institutions. Certain
penalties apply for failure to furnish correct information and for failure to
include reportable payments in income. Each holder of Shares should consult with
his or her own tax advisor as to his or her qualification for exemption from
backup withholding and the procedure for obtaining such exemption. Tendering
holders of Shares may be able to prevent backup withholding by completing the
Substitute Form W-9 included in the Letter of Transmittal. See Section 3.
 
                                       13
<PAGE>   14
 
     6.  PRICE RANGE OF SHARES.  The Shares are included in the Nasdaq National
Market under the symbol "ABCO". The following table sets forth, for the periods
indicated, the reported high and low closing sales prices per Share on the
Nasdaq National Market (i) as reported in the Company's Annual Report on Form
10-K with respect to the fiscal years ended December 31, 1998 and 1997 and (ii)
as reported by published financial sources with respect to the period after
December 31, 1998.
 
<TABLE>
<CAPTION>
                                                            HIGH        LOW
                                                           -------    -------
<S>                                                        <C>        <C>
1997:
  First Quarter..........................................  $29.00     $    23.375
  Second Quarter.........................................   29.50          24.75
  Third Quarter..........................................   30.125         26.00
  Fourth Quarter.........................................   30.75          25.00
1998:
  First Quarter..........................................  $30.50     $    25.50
  Second Quarter.........................................   34.75          28.375
  Third Quarter..........................................   31.50          23.00
  Fourth Quarter.........................................   24.75          20.00
1999:
  First Quarter..........................................  $24.50     $    18.625
  Second Quarter (through April 12)......................  $35.125    $    18.50
</TABLE>
 
     On April 7, 1999, the last full day of trading prior to the public
announcement of the execution of the Merger Agreement, the closing sales price
per Share on the Nasdaq National Market as reported by published financial
sources was $21.875. On April 12, 1999, the last full day of trading prior to
the commencement of the Offer, the last reported sales price per Share was
$35.0625. HOLDERS OF SHARES ARE URGED TO OBTAIN CURRENT MARKET QUOTATIONS FOR
THE SHARES.
 
     The Company has never paid cash dividends on the Shares. The Company's
credit agreement prohibits the payment of cash dividends on the Shares. In
addition, the Merger Agreement provides that the Company will not declare, set
aside or pay any dividends on, or make any other distributions in respect of,
its capital stock, including the Shares. See Section 14.
 
     7.  EFFECT OF THE OFFER ON THE MARKET FOR THE SHARES, INCLUSION IN THE
NASDAQ NATIONAL MARKET AND EXCHANGE ACT REGISTRATION.  The purchase of Shares
pursuant to the Offer will reduce the number of Shares that might otherwise
trade publicly and the number of holders of Shares, and could adversely affect
the liquidity and market value of the remaining Shares held by stockholders
other than Purchaser.
 
     The Shares are currently listed on the Nasdaq National Market, which
constitutes the principal trading market for the Shares. Depending upon
aggregate market value and the number of Shares not purchased pursuant to the
Offer, the Shares may no longer meet the quantitative maintenance criteria of
the Nasdaq National Market for continued inclusion in the Nasdaq National Market
and may cease to be authorized for quotation on such market. If, as a result of
the purchase of Shares pursuant to the Offer, the Shares no longer meet the
criteria for continuing inclusion in the Nasdaq National Market, the market for
the Shares could be adversely affected. According to the Nasdaq National
Market's published guidelines, in order for the Shares to be eligible for
continued inclusion in the Nasdaq National Market, there must continue to be,
among other things, (i) at least 1,100,000 publicly held Shares, held by at
least 400 round lot stockholders, with a market value of at least $15 million,
or (ii) net tangibles assets of at least $4 million, at least 750,000 publicly
held Shares, held by at least 400 round lot stockholders, with a market value of
at least $5 million. If the Shares are no longer eligible for inclusion in the
Nasdaq National Market, they may nevertheless continue to be included in the
Nasdaq SmallCap Market unless, among other things, the number of publicly held
Shares is less than 500,000, or there are fewer than 300 round lot stockholders
in total. If the Shares are no longer eligible for inclusion in the Nasdaq
National Market or the Nasdaq SmallCap Market, the Shares might still be quoted
on the OTC Bulletin Board. According to the Company, there were approximately 80
holders of record of Shares as of March 17, 1999. If, as a result of the
purchase of Shares pursuant to the Offer, the Shares no
 
                                       14
<PAGE>   15
 
longer meet the requirements of the Nasdaq National Market for continued listing
and the listing of Shares is discontinued, the market for the Shares could be
adversely affected.
 
     If the Nasdaq National Market were to delist the Shares (which Purchaser
intends to cause the Company to seek if it acquires control of the Company and
the Shares no longer meet the Nasdaq National Market listing requirements), it
is possible that the Shares would trade on another securities exchange or in the
over-the-counter market and that price quotations for the Shares would be
available from other sources. The extent of the public market for the Shares and
availability of such quotations would, however, depend upon such factors as the
number of holders and/or the aggregate market value of the publicly held Shares
at such time, the interest in maintaining a market in the Shares on the part of
securities firms, the possible termination of registration of the Shares under
the Exchange Act, as described below, and other factors.
 
     The Shares are currently registered under the Exchange Act. Such
registration may be terminated upon application by the Company to the Commission
if there are fewer than 300 record holders of such Shares. It is the intention
of Purchaser to seek to cause an application for such termination to be made as
soon after consummation of the Offer as the requirements for termination of
registration of such Shares are met. If such registration were terminated, the
Company would no longer legally be required to disclose publicly, in proxy
materials distributed to stockholders, the information which it now must provide
under the Exchange Act or to make public disclosure of financial and other
information in annual, quarterly and other reports required to be filed with the
Commission under the Exchange Act; the Company would no longer be subject to
Rule 13e-3 under the Exchange Act relating to "going private" transactions; and
the officers, directors and 10% stockholders of the Company would no longer be
subject to the "short swing" insider trading reporting and profit recovery
provisions of the Exchange Act. Furthermore, if such registration were
terminated, persons holding "restricted securities" of the Company may be
deprived of their ability to dispose of such securities under Rule 144 or Rule
144A promulgated under the Securities Act of 1933, as amended.
 
     If registration of the Shares has not been terminated prior to the Merger,
then following the consummation of the Merger the Shares will no longer be
included in any tier of The Nasdaq Stock Market, Inc. and the registration of
the Shares under the Exchange Act will be terminated.
 
     The Shares are currently "margin securities" under the regulation of the
Board of Governors of the Federal Reserve System (the "Federal Reserve Board"),
which has the effect, among other things, of allowing brokers to extend credit
on the collateral of such Shares. Depending upon factors similar to those
described above regarding listing and market quotations, it is possible that,
following the Offer, the Shares would no longer constitute "margin securities"
for the purposes of the margin regulations of the Federal Reserve Board and
therefore could no longer be used as collateral for loans made by brokers. If
registration of Shares under the Exchange Act were terminated, such Shares would
no longer be "margin securities."
 
     8.  CERTAIN INFORMATION CONCERNING THE COMPANY.  Except as otherwise set
forth herein, the information concerning the Company contained in this Offer to
Purchase, including financial information, has been furnished by the Company or
has been taken from or based upon publicly available documents and records on
file with the Commission and other public sources. Although none of Purchaser,
Parent or Onex has any knowledge that would indicate that statements contained
herein based upon such documents are untrue, none of Purchaser, Parent or Onex
assumes any responsibility for the accuracy or completeness of the information
concerning the Company furnished by the Company or contained in such documents
and records or for any failure by the Company to disclose events which may have
occurred or may affect the significance or accuracy of any such information but
which are unknown to Purchaser, Parent or Onex.
 
     The Company is a Delaware corporation with its principal executive offices
located at 1150 State Docks Road, Eufaula, Alabama 36027. The Company is a
diversified manufacturer and marketer of construction products and services for
non-residential and residential applications. The Company designs, manufactures
and sells metal building systems, which consist of structural framing and wall
and roof panels, for industrial, commercial and institutional markets. The
Company's metal building systems are generally custom-designed to meet the
specific needs of the end-user and to allow for easy on-site assembly by
builders and independent erectors. The Company markets its metal building
systems nationwide through approximately 1,120 authorized builder/dealers. The
Company has a separate roofing products sales, engineering and customer
                                       15
<PAGE>   16
 
service organization, which markets and sells the Company's roofing products to
its builder/dealer network and approximately 370 preferred roofing contractors.
The Company also provides specialty engineering services for large, complex
building structures, manufactures and markets mini-warehouses to serve the self-
storage market and secondary building components to serve the Company's
builder/dealers and roofers as well as the general construction industry, and
paints steel coils. In addition, the Company manufactures and markets steel
sectional upward acting doors for residential, commercial and self-storage
applications, as well as light gauge steel framing systems and roof trusses. The
Company also operates an ICC-licensed trucking subsidiary. The Company markets
its products throughout North America and in selected international countries.
 
     Set forth below is certain summary consolidated financial data with respect
to the Company excerpted from financial information contained in the Company's
Annual Report on Form 10-K for the fiscal year ended December 31, 1998. More
comprehensive financial information is included in such report and other
documents filed by the Company with the Commission, and the following summary is
qualified in its entirety by reference to such report and such other documents
and all the financial information (including any related notes) contained
therein. Such report and other documents should be available for inspection and
copies thereof should be obtainable in the manner set forth below.
 
                           AMERICAN BUILDINGS COMPANY
 
                SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA
 
<TABLE>
<CAPTION>
                                                        YEAR ENDED DECEMBER 31,
                                          ----------------------------------------------------
                                            1998       1997       1996       1995       1994
                                          --------   --------   --------   --------   --------
                                                 (IN THOUSANDS, EXCEPT PER SHARE DATA)
<S>                                       <C>        <C>        <C>        <C>        <C>
STATEMENT OF OPERATIONS DATA:
Net sales...............................  $440,660   $311,967   $272,991   $281,450   $204,666
                                          --------   --------   --------   --------   --------
Costs and expenses:
  Cost of sales.........................   368,941    256,285    228,321    228,088    164,694
  Selling, general and administrative...    37,885     27,607     24,190     26,567     21,830
                                          --------   --------   --------   --------   --------
                                           406,826    283,892    252,511    254,655    186,524
                                          --------   --------   --------   --------   --------
Operating income........................    33,834     28,075     20,480     26,795     18,142
Interest expense (income), net..........     4,981      1,061        143       (175)     1,369
                                          --------   --------   --------   --------   --------
Income from continuing operations before
  income taxes..........................    28,853     27,014     20,337     26,970     16,773
Provision for income taxes(1)...........    11,108     10,401      7,830      9,380      6,318
                                          --------   --------   --------   --------   --------
Income for continuing operations........    17,745     16,613     12,507     17,590     10,455
Discontinued operations(3):
  Loss from operations..................    (1,404)      (762)       (60)        --         --
  Loss on disposal......................    (1,746)        --         --         --         --
                                          --------   --------   --------   --------   --------
Income before extraordinary item(2).....    14,595     15,851     12,447     17,590     10,445
Extraordinary loss on early
  extinguishment of long-term debt(2)...        --         --         --         --     (2,425)
                                          --------   --------   --------   --------   --------
Net income(1)...........................  $ 14,595   $ 15,851   $ 12,447   $ 17,590   $  8,030
                                          ========   ========   ========   ========   ========
</TABLE>
 
                                       16
<PAGE>   17
 
<TABLE>
<CAPTION>
                                                        YEAR ENDED DECEMBER 31,
                                          ----------------------------------------------------
                                            1998       1997       1996       1995       1994
                                          --------   --------   --------   --------   --------
                                                 (IN THOUSANDS, EXCEPT PER SHARE DATA)
<S>                                       <C>        <C>        <C>        <C>        <C>
Earnings per share -- Diluted(4):
  Income from continuing
     operations(1)......................  $   3.15   $   2.94   $   2.07   $   2.68   $   1.81
Discontinued operations(3):
  Loss from operations..................     (0.25)     (0.13)     (0.01)        --         --
  Loss on disposal......................     (0.31)        --         --         --         --
                                          --------   --------   --------   --------   --------
Income before extraordinary item(2).....  $   2.59   $   2.81   $   2.06   $   2.68   $   1.81
Extraordinary loss on early
  extinguishment of long-term debt(2)...        --         --         --         --      (0.42)
                                          --------   --------   --------   --------   --------
Net income per common and common
  equivalent share(1)(4)................  $   2.59   $   2.81   $   2.06   $   2.68   $   1.39
                                          ========   ========   ========   ========   ========
Weighted average number of common
  and common equivalent shares
  outstanding -- Diluted(4).............     5,629      5,649      6,040      6,554      5,780
                                          ========   ========   ========   ========   ========
</TABLE>
 
<TABLE>
<CAPTION>
                                                           AS OF DECEMBER 31,
                                           ---------------------------------------------------
                                             1998       1997       1996       1995      1994
                                           --------   --------   --------   --------   -------
                                                             (IN THOUSANDS)
<S>                                        <C>        <C>        <C>        <C>        <C>
BALANCE SHEET DATA:
Working capital..........................  $ 46,060   $ 34,293   $ 12,965   $ 27,116   $18,182
Total assets.............................   214,716    209,164    100,681    101,343    85,149
Current maturities of long-term
  debt(5)................................     5,236     13,839        970        970     1,863
Long-term debt, net of current
  maturities.............................    67,774     71,395     10,753      7,760    12,376
Stockholders' equity(6)..................    70,745     55,796     41,466     53,511    37,075
</TABLE>
 
- ---------------
(1) In 1995, the Company eliminated a valuation allowance on net operating loss
    carry forwards which resulted in a one-time reduction of its tax provision
    and corresponding increase in net income of $1,005,000, or $0.15 per share.
 
(2) In 1994, the Company incurred an extraordinary loss of $2,425,000 (net of
    applicable tax benefit of $1,436,000), resulting from the write-off of the
    deferred financing costs and unamortized discount related to the early
    extinguishment of its remaining senior notes which were repaid with the
    proceeds from the Company's initial public offering.
 
(3) In December 1998, the Company announced the closing of its American Modular
    Technologies division ("AMT"), which it had acquired in November 1996. The
    transaction has been accounted for as a Discontinued Operation and resulted
    in the Company recording a loss from operations of $1,404,000, net of
    applicable tax benefits of $878,000, and a loss from disposal of
    discontinued operation of $1,764,000, net of applicable tax benefit of
    $1,094,000, in 1998. Data for 1996 and 1997 were restated accordingly.
 
(4) The share and per share information for 1996, 1995 and 1994 has been
    restated to reflect share and per share information in accordance with
    Statement of Financial Accounting Standards No. 128, "Earnings per Share,"
    which was required to be adopted by the Company effective with its financial
    statements for the year ended December 31, 1997.
 
(5) Includes $10,624,000 at December 31, 1997 used to cash collateralize letters
    of credit issued by its previous lenders until replacement letters of credit
    were issued. As replacement letters of credit were issued in 1998, the cash
    was used to pay down the credit facility.
 
(6) Includes a reduction of $28,688,000, $28,451,000, $26,531,000 and $1,071,000
    in 1998, 1997, 1996 and 1995, respectively, which represents Treasury Stock
    purchased by the Company.
 
                                       17
<PAGE>   18
 
     Set forth below is certain summary consolidated financial data of the
Company for the three months ended March 31, 1999 and 1998 and as of March 31,
1999, as publicly announced by the Company on April 13, 1999.
 
<TABLE>
<CAPTION>
                                                             THREE MONTHS ENDED
                                                                 MARCH 31,
                                                           ----------------------
                                                             1999         1998
                                                           ---------    ---------
                                                               (IN THOUSANDS,
                                                           EXCEPT PER SHARE DATA)
<S>                                                        <C>          <C>
STATEMENT OF OPERATIONS DATA:
Net sales................................................   $95,871      $95,853
Operating income.........................................     4,838        4,413
Income from continuing operations........................     2,295        1,929
Loss from operations of discontinued business............        --         (295)
Net income...............................................   $ 2,295      $ 1,634
                                                            =======      =======
PER SHARE DATA -- DILUTED
Income from continuing operations........................   $  0.42      $  0.34
Loss from operations of discontinued business............        --        (0.05)
                                                            -------      -------
Net income...............................................   $  0.42      $  0.29
                                                            =======      =======
Weighted average Shares -- Diluted.......................     5,451        5,633
</TABLE>
 
<TABLE>
<CAPTION>
                                                                MARCH 31,
                                                                   1999
                                                              --------------
                                                              (IN THOUSANDS)
<S>                                                           <C>
BALANCE SHEET DATA:
Cash........................................................     $  3,611
Working capital, excluding cash.............................       42,190
Long-term debt..............................................       71,260
Total equity (net of treasury stock)........................       68,333
Treasury stock..............................................      (33,406)
</TABLE>
 
     Other Information.  The Company is subject to the informational
requirements of the Exchange Act and in accordance therewith, files periodic
reports, proxy statements and other information with the Commission relating to
its business, financial condition and other matters. The Company is required to
disclose in such proxy statements certain information, as of particular dates,
concerning the Company's directors and officers, their remuneration, stock
options granted to them, the principal holders of the Company's securities and
any material interests of such persons in transactions with the Company. Such
reports, proxy statements and other information may be inspected at the public
reference facilities maintained by the Commission in Washington, D.C., and at
the regional offices of the Commission located in New York, New York and
Chicago, Illinois. Please call the Commission at 1-800-SEC-0330 for further
information on the public reference rooms. These Commission filings are also
available to the public from commercial document retrieval services. The
Commission filings are also available at the Internet web site maintained by the
Commission at "http://www.sec.gov".
 
     Information Provided to Onex.  The Company does not as a matter of course
publicly disclose its internal budget and strategic plans as to future revenues,
earnings or financial condition. However, in the course of discussing the
proposed transaction with Onex, the Company discussed with Onex certain business
and financial information that Onex believes was not and is not publicly
available. Such information included, among other things, certain budget and
strategic business plan information (together, the "Company Plan") prepared by
management of the Company. The Company Plan does not take into account any of
the potential effects of the Merger. The Company Plan discloses, among other
things, that management's revenue estimates for calendar years 1999 and 2000 are
approximately $464.3 million and $532.1 million, respectively, and that
estimated net income for the same periods is approximately $18.9 million and
$25.7 million, respectively.
 
                                       18
<PAGE>   19
 
     THE FOREGOING ESTIMATES CONSTITUTE FORWARD-LOOKING STATEMENTS THAT INVOLVE
RISKS AND UNCERTAINTIES. THESE RISKS AND UNCERTAINTIES ARE DISCUSSED IN GREATER
DETAIL IN THE COMPANY'S PERIODIC FILINGS WITH THE COMMISSION. THE COMPANY PLAN
WAS PREPARED SOLELY FOR INTERNAL USE AND NOT WITH A VIEW TO PUBLIC DISCLOSURE OR
TO COMPLY WITH PUBLISHED GUIDELINES OF THE COMMISSION OR THE GUIDELINES
ESTABLISHED BY THE AMERICAN INSTITUTE OF CERTIFIED PUBLIC ACCOUNTANTS. THE
ASSUMPTIONS UNDERLYING THE COMPANY ESTIMATES ARE INHERENTLY SUBJECT TO
SIGNIFICANT BUSINESS, ECONOMIC AND COMPETITIVE UNCERTAINTIES AND CONTINGENCIES
(INCLUDING FINANCIAL MARKET CONDITIONS), MANY OF WHICH ARE BEYOND THE CONTROL OF
THE COMPANY. THE COMPANY PLAN INFORMATION IS INCLUDED HEREIN ONLY BECAUSE SUCH
INFORMATION WAS PROVIDED TO ONEX. NONE OF THE COMPANY, ONEX, PURCHASER OR PARENT
OR ANY PARTY TO WHOM THE COMPANY PLAN INFORMATION WAS PROVIDED GIVES ANY
ASSURANCE AS TO THE ACCURACY OF SUCH INFORMATION. THE COMPANY HAS INFORMED ONEX
THAT THE COMPANY'S INTERNAL FINANCIAL FORECASTS (UPON WHICH THE ESTIMATES
PROVIDED TO ONEX WERE BASED) ARE, IN GENERAL, PREPARED SOLELY FOR INTERNAL USE
AND BUDGETING AND OTHER MANAGEMENT DECISION-MAKING PURPOSES, AND ARE SUBJECTIVE
IN MANY RESPECTS AND THUS SUSCEPTIBLE TO VARIOUS INTERPRETATIONS AND PERIODIC
REVISION BASED ON ACTUAL EXPERIENCE AND BUSINESS DEVELOPMENTS. THERE CAN BE NO
ASSURANCE THAT THE COMPANY PLAN WILL BE REALIZED, AND ACTUAL RESULTS MAY DIFFER
MATERIALLY FROM THOSE SET FORTH ABOVE. THE COMPANY'S INDEPENDENT AUDITORS HAVE
NOT EXAMINED OR COMPILED THE ABOVE ESTIMATES AND ACCORDINGLY ASSUME NO
RESPONSIBILITY FOR THEM. FOR THESE REASONS, AS WELL AS THE BASES ON WHICH SUCH
PLANS WERE COMPLETED, THE INCLUSION OF SUCH PROJECTIONS HEREIN SHOULD NOT BE
REGARDED AS FACT OR AN INDICATION THAT ONEX, PURCHASER OR PARENT OR ANY OTHER
PARTY WHO RECEIVED SUCH INFORMATION CONSIDERS IT AN ACCURATE PREDICTION OF
FUTURE EVENTS. NONE OF THE COMPANY, ONEX, PURCHASER OR PARENT OR THE COMPANY'S
FINANCIAL ADVISOR ASSUMES ANY RESPONSIBILITY FOR THE ACCURACY OR VALIDITY OF ANY
OF THE ESTIMATES.
 
     9.  CERTAIN INFORMATION CONCERNING PARENT, PURCHASER AND ONEX.  Parent and
Purchaser, each a Delaware corporation formed on April 5, 1999, were formed by
Onex for the purpose of acquiring the Company and have not conducted any
unrelated activities since their formation. All of the outstanding common stock
of Purchaser is owned by Parent. All of the outstanding common stock of Parent
is owned by Onex American Holdings LLC, an indirect wholly-owned subsidiary of
Onex.
 
     Onex is a diversified company with annual consolidated revenues of
$(Cdn.)8.8 billion, consolidated assets of $(Cdn.)6.8 billion and 53,000
employees. Onex was ranked the 9th largest company in Canada in The Financial
Post 500. It operates through autonomous subsidiaries that are leaders in their
industries. They include Sky Chefs, Inc., Celestica Inc., ClientLogic, Lantic
Sugar Limited, Dura Automotive Systems, Inc., Tower Automotive, Inc., Phoenix
Pictures Inc. and Vencap, Inc. Onex shares trade on the Toronto and Montreal
exchanges under the stock symbol OCX.
 
     Onex is not subject to the informational requirements of the Exchange Act.
However, it is subject to the informational requirements of various securities
laws in Canada and files annual, quarterly and special reports, proxy statements
and other information with the Canadian securities authorities (the "CSAs"). Any
reports, statements or other information that Onex files with the CSAs are
electronically available through the Canadian System for Electronic Document
Analysis and Retrieval ("SEDAR") on the Internet web site maintained by the CSAs
at "http://www.sedar.com". The financial information concerning Onex available
through SEDAR is prepared in accordance with generally accepted accounting
principles in Canada, which differ from generally accepted accounting principles
in the United States. The information filed by Onex with the CSAs is not
incorporated by reference into this Offer to Purchase.
 
                                       19
<PAGE>   20
 
     The business address of each of Parent and Purchaser is c/o Onex Investment
Corporation, 712 Fifth Avenue, 40th Floor, New York, New York 10019 and of Onex
is Canada Trust Tower, 161 Bay Street, 49th Floor, Toronto, Ontario M5J 2S1
Canada. Schedule I to this Offer to Purchase contains information with respect
to the executive officers and directors of Parent, Purchaser and Onex.
 
     Except as otherwise set forth in this Offer to Purchase (including Schedule
I hereto), none of Parent, Purchaser or Onex, nor, to the best knowledge of
Parent, Purchaser and Onex, any of the persons listed in Schedule I hereto, owns
or has any right to acquire any Shares, and none of them has effected any
transaction in the Shares during the past 60 days.
 
     Except as set forth in this Offer to Purchase, none of Parent, Purchaser or
Onex, nor, to the best knowledge of Parent, Purchaser and Onex, any of the
persons listed in Schedule I hereto, has any contract, arrangement,
understanding or relationship with any other person with respect to any
securities of the Company, including, without limitation, any contract,
arrangement, understanding or relationship concerning the transfer or the voting
of any securities of the Company, joint ventures, loan or option arrangements,
puts or calls, guaranties of loans, guaranties against loss or the giving or
withholding of proxies. Except as set forth in this Offer to Purchase, none of
Parent, Purchaser or Onex, nor, to the best knowledge of Parent, Purchaser and
Onex, any of the persons listed in Schedule I hereto, has had any transactions
with the Company or any of its executive officers, directors or affiliates that
would require reporting under the rules of the Commission.
 
     Except as set forth in this Offer to Purchase, there have been no
contracts, negotiations or transactions between any of Parent, Purchaser or
Onex, or their respective subsidiaries, or, to the best knowledge of Parent,
Purchaser and Onex, any of the persons listed in Schedule I hereto, on the one
hand, and the Company or its executive officers, directors or affiliates, on the
other hand, concerning a merger, consolidation or acquisition, tender offer or
other acquisition of securities, election of directors, or a sale or other
transfer of a material amount of assets.
 
     10.  SOURCE AND AMOUNT OF FUNDS.  The total amount of funds required by
Purchaser to purchase all Shares that may be tendered pursuant to the Offer and
in the Merger, and to pay the related fees and expenses, is estimated to be
approximately $215 million.
 
     Purchaser intends (i) to finance the Offer and certain related expenses
with (a) a senior credit facility of $110 million secured by the Shares being
tendered (the "Tender Facility") and (b) a capital contribution from Onex and
(ii) to finance the Merger and certain related expenses and to cause the
Surviving Corporation to refinance certain indebtedness of the Company, to repay
amounts owing under the Tender Facility and to provide for other general
corporate purposes of the Surviving Corporation with senior secured credit
facilities of up to $210 million (the "Merger Facilities"), comprised of a $30
million five-year revolving credit facility, a $45 million five-year term loan
and a $135 million six-and-one-half-year term loan (the Tender Facility and the
Merger Facilities are collectively referred to as the "Credit Facilities"). The
Credit Facilities are to be provided pursuant to a commitment letter dated April
7, 1999 (the "Commitment Letter") with Canadian Imperial Bank of Commerce
("CIBC").
 
     The funding of the Credit Facilities will be subject to customary closing
conditions, including, among others, (i) the negotiation, execution and delivery
on or before June 15, 1999 of definitive documentation with respect to the
Credit Facilities satisfactory to CIBC and its counsel, (ii) completion and
satisfaction by CIBC with respect to a due diligence investigation of the legal
structure of the transaction (including tax matters related thereto), (iii) the
absence of any material adverse change since December 31, 1998 in or affecting
the business, results of operations, assets, liabilities, condition (financial
or otherwise) or prospects of the Company and its subsidiaries taken as a whole,
or Parent and Purchaser, taken together, (iv) the absence of a material
disruption of or material adverse change in financial, banking or capital market
conditions that, in the judgment of CIBC, could materially impair the
syndication of the Credit Facilities and (v) the receipt of all necessary
governmental and third party approvals in connection with the Credit Facilities
and the consummation of the Offer.
 
     In addition to the conditions set forth in the preceding paragraph, the
funding of the Tender Facility is subject to additional conditions, including,
among others, (i) the receipt by Purchaser of a specified capital
 
                                       20
<PAGE>   21
 
contribution from Onex, (ii) the receipt by CIBC of a satisfactory pro forma
projected balance sheet of the Surviving Corporation as of the Effective Time,
satisfactory audited and interim unaudited financial statements of the Company
and a satisfactory business plan for fiscal years 1999-2003 for the Surviving
Corporation, (iii) the fees and expenses for the Offer and the Merger not
exceeding $14.4 million and (iv) the receipt by CIBC of satisfactory
confirmation of continued accuracy of previously completed environmental due
diligence.
 
     It is anticipated that the definitive agreements relating to the Credit
Facilities will contain customary representations and warranties and certain
covenants, including limitations on indebtedness, liens, restricted payments and
similar matters, as well as certain mandatory prepayment obligations customary
for transactions of this nature.
 
     Although Parent expects that the Credit Facilities will be available to
provide funds for the consummation of the Offer and the Merger in accordance
with their respective terms, there can be no assurance that the Credit
Facilities will be consummated. In the event the Credit Facilities are not
consummated, Onex has agreed to provide or cause to be provided to Purchaser the
funds necessary to purchase all outstanding Shares (on a fully-diluted basis)
pursuant to the Offer and the Merger and to pay all fees and expenses related to
the Offer, the Merger and the other transactions contemplated by the Merger
Agreement. Onex has sufficient cash and other liquid assets to satisfy such
obligations. The Offer is not conditioned upon the availability of financing
under the Credit Facilities or otherwise.
 
     11.  BACKGROUND OF THE OFFER; PAST CONTACTS, TRANSACTIONS OR NEGOTIATIONS
WITH THE COMPANY.  On January 4, 1999, a representative of CIBC contacted
William L. Selden, the Company's Chairman of the Board, to advise Mr. Selden
that Onex had expressed interest in looking at the Company. Mr. Selden informed
CIBC's representative that he would be willing to meet with Onex, and Mr. Selden
was then contacted by Mark Hilson, a Vice President of Onex. On January 12,
1999, Mr. Hilson and Nigel Wright, a principal of Onex, met with Mr. Selden at
his offices in Westport, Connecticut to discuss the Company. Messrs. Hilson and
Wright spoke generally of Onex's possible interest in pursuing an acquisition of
the Company, but did not discuss price or structure.
 
     On January 28, 1999, Messrs. Hilson and Wright contacted Mr. Selden and
scheduled a telephone call for February 1, 1999. On the February 1, 1999
telephone call, Messrs. Hilson, Wright and Selden discussed generally the
Company's operations and historical results. Messrs. Hilson and Wright again
expressed Onex's possible interest in pursuing an acquisition of the Company,
based upon their research of the industry and publicly available information
about the Company. Mr. Selden requested that Onex express its interest in
writing.
 
     On February 3, 1999, Onex delivered a letter to Mr. Selden proposing an all
cash acquisition of the Company for $30-$31 per Share through a tender offer,
subject to completion of due diligence. The letter requested that Onex be
granted a 45-day exclusivity period in which to complete due diligence and
negotiate a transaction. Messrs. Hilson and Wright then had a telephone
conversation with Mr. Selden, during which Mr. Selden stated that another party
had approached him regarding its potential interest in acquiring the Company. He
gave no details as to the identity of the party or the nature or terms of its
interest. Mr. Selden indicated that he would send both proposals to the Board
and that the Board would determine the process to adopt.
 
     During the first week of February, 1999, Mr. Selden had several phone
conversations with Messrs. Hilson and Wright. Mr. Selden subsequently contacted
Messrs. Hilson and Wright and asked them to be more specific concerning how Onex
would finance this purchase as well as what financial incentives it would
provide the existing Company management. In a separate telephone conversation,
Mr. Selden indicated to Messrs. Hilson and Wright that he would send the
proposals received by him to the full Board by the middle of the following week.
He also stated that the Board would retain Warburg Dillon Read LLC ("WDR") to
provide financial advice and a fairness opinion.
 
     On February 11, 1999, Onex delivered a letter to Mr. Selden responding to
his questions about Onex's financing and management incentives. On February 19,
1999, Messrs. Hilson, Wright and Selden had a
 
                                       21
<PAGE>   22
 
telephone conversation, during which Onex requested the Company's consent to
contact CIBC to discuss CIBC's interest in possibly financing Onex's acquisition
of the Company. This consent was given on March 24, 1999.
 
     On February 25, 1999, Onex delivered a letter to Mr. Selden reiterating its
interest in the Company and further detailing its future plans for the Company
and incentives for management. Onex proposed a 10-day exclusivity period to
allow Onex to complete due diligence and make a final decision whether to
proceed with a transaction. Onex stressed that it did not want to participate in
an auction process.
 
     On March 4, 1999, Messrs. Hilson and Wright had two conversations with Mr.
Selden. In the first conversation, Mr. Selden informed Messrs. Hilson and Wright
that a Board meeting would be held later that day and that the Board had
received more than one firm expression of interest. Messrs. Hilson and Wright
advised Mr. Selden that an affiliate of Onex had acquired 4.9% of the Shares. In
the second conversation, Mr. Selden advised Onex that the Board had received and
reviewed three serious expressions of interest. Mr. Selden informed Messrs.
Hilson and Wright that the Board had instructed management to meet with each
interested party and to report back to the Board. He invited the Onex
representatives to meet with Robert Ammerman, the Company's chief executive
officer, and R. Charles Blackmon, Jr., the Company's Executive Vice
President -- Chief Financial Officer, at the offices of the Company's counsel,
Fulbright & Jaworski L.L.P. ("F&J"), in New York City on March 12, 1999, subject
to executing a satisfactory confidentiality agreement. Mr. Selden stated that
Messrs. Ammerman and Blackmon would make a presentation on the Company and
assess the proposals of each of the three parties that had expressed an
interest.
 
     On March 5, 1999, Barbara Alexander of WDR advised Mr. Hilson that WDR had
been engaged by the Company to advise the Board in connection with the proposals
received by it.
 
     As of March 8, 1999, Onex entered into a confidentiality agreement with the
Company. See Section 13.
 
     On March 9, 1999, Onex received a letter from WDR confirming the date and
time of Onex's meeting with the Company's management. The letter also set forth
an agenda for the meeting, which included a presentation by the Company's
management as well as a presentation by Onex with respect to its financing for
and ability to close a transaction quickly and its plans for the Company and the
Company's management and employees post-closing.
 
     Messrs. Ammerman and Blackmon, together with WDR, met with Onex on March
12, 1999 in New York City. The meeting involved a general discussion of the
Company's operations, financial performance, 1999 budget and five year strategic
plan, as well as Onex's proposed plans for the Company and management following
the closing of a transaction. WDR requested that Onex firm up its indication of
interest by March 19, 1999. The Company's management and WDR had several
follow-up conversations with Onex during the week of March 15 to provide
additional information and respond to additional questions.
 
     On March 18, 1999, Onex delivered a letter to WDR expanding on its proposal
with respect to management incentives to be provided by Onex. Subsequently, Onex
orally advised WDR that Onex was prepared to pay $32 per Share.
 
     On March 24, 1999, David Dickson of WDR notified Onex that the Board had
determined to give Onex an exclusive period of up to four weeks to complete its
due diligence and negotiate an agreement. Onex was also advised that it could
contact CIBC about financing a proposed acquisition. Onex and the Company set up
a series of due diligence meetings, beginning with a meeting with the Company's
full management team on March 31, 1999 in Atlanta, Georgia, to be followed by
visits to the Company's facilities during the week of April 5, 1999.
 
     On March 25, 1999, WDR notified Onex that the Company had received a higher
unsolicited offer and stated that, as a result, the Company could not negotiate
with Onex on an exclusive basis. WDR inquired whether Onex would be interested
in participating in an auction or increasing its offer.
 
     During March 25 to 27, 1999, Onex had several telephone conversations with
Messrs. Ammerman and Blackmon.
                                       22
<PAGE>   23
 
     On March 26, 1999, Onex orally indicated to WDR that it was raising its
offer to $34, that it would accelerate its due diligence and would be ready to
sign an agreement to acquire the Company by April 2, 1999, but wanted a 4%
topping fee rather than the 3.5% fee proposed in its prior indications of
interest. On the evening of March 28, 1999, Onex reiterated to WDR that it would
not participate in an auction.
 
     From March 29 to March 31, 1999, Messrs. Hilson and Wright met with the
Company's management and visited the Company's Eufaula, Alabama, Little Rock,
Arkansas, and Birmingham, Alabama facilities.
 
     On March 29, 1999, Kaye, Scholer, Fierman, Hays & Handler, LLP, counsel for
Onex ("KSFH&H"), delivered a proposed Agreement and Plan of Merger to F&J. Later
that day, WDR contacted Onex, indicating that another party had increased its
bid; Onex subsequently increased its bid to $34.50, but said it wanted an
exclusive negotiating right through April 5, 1999. That evening, F&J sent its
version of a proposed Agreement and Plan of Merger (the "Proposed Agreement") to
KSFH&H.
 
     On March 30, 1999, the Company entered into an exclusivity agreement (the
"Exclusivity Agreement") with Onex, giving Onex an exclusive negotiating right
through April 5, 1999, but giving the Board the right to terminate the exclusive
right if it determined it was required to do so in the exercise of its fiduciary
duties. On March 30, 1999, KSFH&H began to review documents at the data room at
F&J.
 
     On March 31, 1999, WDR sent a letter to Onex notifying it that the Company
was terminating the Exclusivity Agreement based on its fiduciary duty to
consider another party's offer, and that the Board of Directors had scheduled a
meeting for April 7, 1999 at 1:00 p.m. to consider any proposals and to take
whatever action it deemed to be in the best interests of stockholders.
 
     On April 1, 1999 and over the ensuing days, Messrs. Hilson and Wright had
several conversations with Messrs. Ammerman and Blackmon regarding follow-up
questions, and KSFH&H continued to review the due diligence documents made
available by F&J and the Company. On April 5, 1999, Messrs. Ammerman and
Blackmon met with members of Onex management, including Messrs. Hilson and
Wright, in Toronto, Canada for further due diligence meetings. On April 5, 1999,
KSFH&H delivered a mark-up of the Proposed Agreement to F&J. Representatives of
Onex continued their due diligence examination of the Company.
 
     On April 6, 1999, Messrs Ammerman and Blackmon had telephone conversations
with representatives of Onex and F&J held discussions with KSFH&H to finalize
the Proposed Agreement.
 
     On April 7, 1999, F&J continued to negotiate with KSFH&H to finalize the
Proposed Agreement. Immediately prior to the scheduled Board meeting, Onex
submitted its offer in writing to the Company.
 
     Following the Board meeting, the Company and Onex signed the Merger
Agreement and the transaction was announced prior to the opening of the Nasdaq
National Market on April 8, 1999.
 
     12.  PURPOSE OF THE OFFER AND THE MERGER; SHORT FORM MERGER; PLANS FOR THE
COMPANY; APPRAISAL RIGHTS; GOING PRIVATE TRANSACTIONS.
 
     Purpose of the Offer and the Merger; Possible Short Form Merger.  The Offer
is being made pursuant to the Merger Agreement. The purpose of the Offer, the
Merger and the Merger Agreement is to enable Parent to acquire control of, and
to own the entire equity interest in, the Company. Upon consummation of the
Merger, the Company will become a wholly-owned subsidiary of Parent and an
indirect wholly-owned subsidiary of Onex. The Offer is intended to increase the
likelihood that the Merger will be effected.
 
     The Board has unanimously (with one director not present) approved the
Merger and adopted the Merger Agreement. Depending upon the number of Shares
purchased by Purchaser pursuant to the Offer, the Board may be required to
submit the Merger Agreement to the Company's stockholders for approval at a
stockholder's meeting convened for that purpose in accordance with the DGCL. If
stockholder approval is required, the Merger Agreement must be approved by a
majority of all votes entitled to be cast at such meeting.
 
     If the Minimum Condition is satisfied, Purchaser will have sufficient
voting power to approve the Merger Agreement at the stockholders' meeting
without the affirmative vote of any other stockholder.
 
                                       23
<PAGE>   24
 
     If Purchaser acquires at least 90% of the Shares, the DGCL permits
Purchaser to consummate the Merger without a stockholders' meeting and without
the approval of, or prior notice to, the other Company stockholders (a "short
form merger"). If Purchaser acquires at least 90% of the outstanding Shares,
Purchaser anticipates that it will take all necessary and appropriate action to
cause the Merger to become effective as soon as reasonably practicable after
such acquisition without a meeting of the Company's stockholders. If, however,
after consummation of the Offer, Purchaser owns less than such number of Shares,
a vote of the Company's stockholders will be required under the DGCL to approve
the Merger, and a significantly longer period will be required to effect the
Merger.
 
     After completion or termination of the Offer, Purchaser reserves the right,
but has no current intention, to acquire or sell Shares in open market or
negotiated transactions. There can be no assurance that Purchaser will acquire
any additional Shares in such circumstances or over what period of time such
additional Shares, if any, might be acquired. As a consequence, unless the
Minimum Condition is satisfied, no assurance can be given as to when the Merger
will be consummated, and similarly no assurance can be given as to when the
Merger Consideration will be paid to stockholders who do not tender their Shares
in the Offer.
 
     Plans for the Company.  The Merger Agreement provides that Purchaser will
be merged with and into the Company following the Offer, and that the
certificate of incorporation of Purchaser will be the certificate of
incorporation of the Surviving Corporation following the Merger (except that the
name of the Surviving Corporation will be changed to American Buildings
Company).
 
     Pursuant to the Merger Agreement, the officers of the Company immediately
prior to the Effective Time will be the initial officers of the Surviving
Corporation, and the directors of Purchaser immediately prior to the Effective
Time will be the directors of the Surviving Corporation, in each case until
their respective successors are duly elected or appointed and qualified.
 
     Upon consummation of the Merger, the Surviving Corporation will become a
wholly-owned subsidiary of Parent, which intends to manage and operate the
Surviving Corporation as an independent operating unit. It is expected that the
business and operations of the Company will, except as set forth in this Offer
to Purchase, be continued by the Surviving Corporation substantially as they are
currently being conducted. Following consummation of the Offer, and thereafter
following the Merger, Parent will continue to evaluate the Company and its
assets, business, operations, properties, policies (including dividend
policies), corporate structure, capitalization, capital expenditures, liquidity
and management and will make such changes as it deems desirable in light of the
circumstances that then exist.
 
     Once the Offer is consummated, if permitted by the NASD and the Exchange
Act, and in any event upon consummation of the Merger, it is the intention of
Purchaser and Parent to cause the Company to file applications to withdraw the
Shares from listing and trading on the Nasdaq National Market and to terminate
the registration of the Shares under the Exchange Act. See Section 7.
 
     Except as otherwise described in this Offer to Purchase, Purchaser has no
current plans or proposals which relate to or would result in: (a) an
extraordinary corporate transaction, such as a merger, reorganization or
liquidation involving the Company or any of its subsidiaries; (b) a sale or
transfer of a material amount of assets of the Company or any of its
subsidiaries outside the ordinary course of business; (c) any change in the
Board or management of the Company; (d) any material change in the present
capitalization or the dividend policy of the Company; (e) any other material
change in the Company's corporate structure or business; or (f) a class of the
Company's securities being delisted from a national securities exchange or
ceasing to be authorized to be quoted in an inter-dealer quotation system of any
registered national securities association.
 
     Appraisal Rights.  Holders of the Shares do not have appraisal rights in
connection with the Offer. However, if the Merger is consummated, holders of the
Shares at the Effective Time of the Merger will have certain rights pursuant to
the provisions of Section 262 of the DGCL to dissent and demand appraisal of,
and to receive payment in cash of the fair value of, their Shares. Dissenting
stockholders of the Company who comply with the applicable statutory procedures
will be entitled to receive a judicial determination of the "fair value" of
their Shares (exclusive of any element of value arising from the accomplishment
or expectation of the Merger) and to receive payment of such fair value in cash,
together with a fair rate of interest thereon, if
 
                                       24
<PAGE>   25
 
any. Any such judicial determination of the fair value of the Shares could be
based upon factors other than, or in addition to, the price per Share to be paid
in the Merger or the market value of the Shares. The value so determined could
be more or less than the price per Share to be paid in the Merger.
 
     In addition, several decisions by Delaware courts have held that, in
certain circumstances, a controlling stockholder of a company involved in a
merger has a fiduciary duty to other stockholders which requires that the merger
be fair to such other stockholders. In determining whether a merger is fair to
minority stockholders, Delaware courts have considered, among other things, the
type and amount of consideration to be received by the stockholders and whether
there was fair dealing among the parties. The Delaware Supreme Court stated in
Weinberger and Rabkin v. Philip A. Hunt Chemical Corp. that the remedy
ordinarily available to minority stockholders in a cash-out merger is the right
to appraisal described above. However, a damages remedy or injunctive relief may
be available if a merger is found to be the product of procedural unfairness,
including fraud, misrepresentation or other misconduct.
 
     Going Private Transactions.  The Commission has adopted Rule 13e-3 under
the Exchange Act, which is applicable to certain "going private" transactions
and which may under certain circumstances be applicable to the Merger or another
business combination following the purchase of the Shares pursuant to the Offer
in which Purchaser seeks to acquire the remaining Shares not held by it. Rule
13e-3 should not be applicable to the Merger if the Merger is consummated within
one year after the expiration or termination of the Offer and the price paid in
the Merger is not less than the per Share price paid pursuant to the Offer.
However, in the event that Purchaser is deemed to have acquired control of the
Company pursuant to the Offer and if the Merger is consummated more than one
year after completion of the Offer or an alternative acquisition transaction is
effected whereby stockholders of the Company receive consideration less than
that paid pursuant to the Offer, in either case at a time when the Shares are
still registered under the Exchange Act, Purchaser may be required to comply
with Rule 13e-3 under the Exchange Act. If Rule 13e-3 were applicable to the
Merger, it would require, among other things, that certain financial information
concerning the Company, and certain information relating to the fairness of the
Merger or such alternative transaction and the consideration offered to the
stockholders of the Company other than Purchaser, Parent and their affiliates in
the Merger or such alternative transaction, be filed with the Commission and
disclosed to stockholders prior to consummation of the Merger or such
alternative transaction. If registration of the Shares under the Exchange Act
were terminated, Rule 13e-3 would be inapplicable to any such transaction.
 
     13.  MERGER AGREEMENT; CERTAIN OTHER AGREEMENTS.  The following are
summaries of the material terms of the Merger Agreement, a letter of undertaking
from Onex to the Company dated April 7, 1999 (the "Letter of Undertaking") and a
confidentiality agreement between Onex and the Company dated as of March 8, 1999
(the "Confidentiality Agreement"). These summaries are not complete descriptions
of the agreements and are qualified in their entirety by reference to the
complete text of the agreements, a copy of each of which is filed as an exhibit
to the Tender Offer Statement on Schedule 14D-1 filed jointly with the
Commission by Parent, Purchaser and Onex, and is incorporated by reference
herein. Capitalized terms not otherwise defined in this Offer to Purchase have
the meanings set forth in the Merger Agreement.
 
  THE MERGER AGREEMENT
 
     The Offer.  The Merger Agreement provides that Purchaser will commence the
Offer and that, upon the terms and subject to the prior satisfaction or waiver
of the conditions of the Offer, Purchaser will purchase all Shares validly
tendered and not withdrawn pursuant to the Offer. The Merger Agreement provides
that, without the written consent of the Company, Purchaser will not (i) waive
the Minimum Condition, (ii) reduce the number of Shares to be purchased in the
Offer, (iii) reduce the Offer Price, (iv) modify or add to the conditions to the
Offer described in Section 15, (v) except as set forth in the following two
sentences, extend the Offer, (vi) change the form of consideration payable in
the Offer or (vii) amend any other term of the Offer in a manner adverse to the
holders of the Shares. However, if on the initially scheduled Expiration Date
any of the conditions to the Offer has not have been satisfied or waived,
Purchaser may, without the consent of the Company, extend the Expiration Date on
one or more occasions for up to 10 Business Days for each extension or for any
period required by any rule, regulation, interpretation or position of the
Commission or its staff applicable to the Offer. In addition, if immediately
prior to the Expiration Date, as it may be
                                       25
<PAGE>   26
 
extended, all of the conditions to Purchaser's obligations to accept for
payment, and to pay for, the Shares are satisfied or waived, but the Shares
tendered and not withdrawn pursuant to the Offer (together with the Shares then
owned by Purchaser and its affiliates) are less than 90% of the outstanding
Shares, Purchaser may extend the Offer for a period of not more than 10 Business
Days.
 
     The Merger.  The Merger Agreement provides that, following the consummation
of the Offer and subject to the terms and conditions set forth therein, at the
Effective Time, Purchaser shall be merged with and into the Company and, as a
result of the Merger, the separate corporate existence of Purchaser shall cease,
and the Company shall continue as the Surviving Corporation as a direct
subsidiary of Parent.
 
     The respective obligations of Parent and Purchaser, on the one hand, and
the Company, on the other hand, to consummate the Merger are subject to the
satisfaction at or prior to the Effective Time of each of the following
conditions: (i) if required by applicable law, the Merger Agreement shall have
been approved and adopted by the affirmative vote of the holders of a majority
of the outstanding Shares; (ii) no statute, rule or regulation shall have been
enacted, promulgated or deemed applicable to the Merger by any governmental
entity which prevents the consummation of the Merger or makes the consummation
of the Merger unlawful, and no temporary restraining order, preliminary or
permanent injunction or other order issued by any court of competent
jurisdiction preventing the consummation of the Merger shall be in effect,
provided, however, that each of the parties is obligated to use reasonable
efforts to prevent the entry of any such injunction or other order and to appeal
as promptly as possible any injunction or other order that may be entered; (iii)
all actions by or in respect of or filings with any U.S. federal governmental
entity required to permit the consummation of the Merger shall have been
completed; and (iv) Purchaser shall have purchased all Shares validly tendered
and not withdrawn pursuant to the Offer, provided, however, this condition in
clause (iv) shall not be applicable to the obligations of Parent or Purchaser
if, in breach of the Merger Agreement or the terms of the Offer, Purchaser fails
to purchase any Shares validly tendered and not withdrawn pursuant to the Offer.
 
     At the Effective Time of the Merger, (i) each issued and outstanding Share
(other than Shares that are held by stockholders properly exercising dissenters'
rights under the DGCL and those referred to in clause (ii) below) shall be
canceled and retired and be converted into the right to receive in cash the
Merger Consideration, (ii) each Share owned by the Company, Parent or Purchaser
or any subsidiary of the Company immediately prior to the Effective Time shall
be canceled and no payment shall be made with respect thereto and (iii) each
share of common stock of Purchaser outstanding immediately prior to the
Effective Time shall be converted into and become one fully paid and
nonassessable share of common stock, par value $.01 per share, of the Surviving
Corporation and shall constitute the only outstanding shares of capital stock of
the Surviving Corporation.
 
     The Company's Board of Directors.  The Merger Agreement provides that
promptly upon the acceptance for payment of, and payment for, Shares by
Purchaser pursuant to the Offer, Purchaser from time to time shall be entitled
to designate such number of directors (rounded up to the next whole number) on
the Board as will give Purchaser, subject to compliance with Section 14(f) of
the Exchange Act, up to that percentage of the total number of directors on the
Board (giving effect to the election of any additional directors described
below) equal to the percentage of then outstanding Shares so accepted for
payment, together with Shares owned by Parent or any of its affiliates, and the
Company will, at such time, cause Purchaser's designees to be so elected by its
existing Board; provided, however, that in the event that such designees are
elected to the Board, until the Effective Time such Board must have at least two
Independent Directors; and provided, further, that if the number of Independent
Directors is reduced below two for any reason whatsoever, the remaining
Independent Director shall be entitled to designate a person to fill such
vacancy who shall be deemed to be an Independent Director for purposes of the
Merger Agreement or, if no Independent Directors then remain, the other
directors shall designate two persons to fill such vacancies who shall not be
officers of the Company or stockholders, affiliates or associates of Purchaser
or Parent, and such persons shall be deemed to be Independent Directors for
purposes of the Merger Agreement. Following the election of Purchaser's
designees and prior to the Effective Time, any amendment or termination of the
Merger Agreement or waiver of any of the Company's rights thereunder shall
require the affirmative vote of a majority of the Independent Directors.
 
                                       26
<PAGE>   27
 
     Stockholders' Meeting.  Pursuant to the Merger Agreement, the Company will,
if required by the DGCL in order to consummate the Merger, as soon as
practicable following the acceptance for payment of, and payment for, shares by
Purchaser pursuant to the Offer, duly call, give notice of, convene and hold a
meeting of its stockholders to consider and vote upon the approval of the Merger
Agreement and the Merger and all other necessary matters (the "Company
Proposals"), with a record date following the acceptance for payment of, and
payment for, Shares pursuant to the Offer. The Merger Agreement provides that
the Company will, if required, as soon as practicable following the expiration
of the Offer, file with the Commission and, when cleared by the Commission, mail
to stockholders, a proxy statement in connection with a meeting of the Company's
stockholders to vote upon the Company Proposals, or an information statement, as
appropriate, satisfying all requirements of the Exchange Act. If Purchaser
acquires at least a majority of the Shares, it will have sufficient voting power
to approve the Merger, even if no other stockholder votes in favor of the
Merger.
 
     The Merger Agreement provides that in the event that Parent acquires at
least 90% of the Shares, pursuant to the Offer or otherwise, Parent, Purchaser
and the Company will, at the request of Parent, take all necessary and
appropriate action to cause the Merger to become effective as soon as
practicable after the Offer, without a meeting of stockholders of the Company,
in accordance with the DGCL.
 
     Options.  Each option to purchase Shares outstanding immediately prior to
the Effective Time (collectively, "Options"), whether or not then vested or
exercisable, shall at the Effective Time be canceled and be converted into the
right to receive an amount in cash in respect thereof equal to the product of
(1) the excess, if any, of the Merger Consideration over the per Share exercise
price thereof and (2) the number of Shares subject thereto immediately prior to
the Effective Time.
 
     Conduct of Business Pending the Merger.  In the Merger Agreement, the
Company has agreed that, during the period from April 7, 1999 to the Effective
Time, it will, and will cause each of its subsidiaries to, carry on their
respective businesses in the usual, regular and ordinary course in substantially
the same manner as heretofore conducted and in compliance with all applicable
laws and regulations, except where the failure to be in compliance would not,
individually or in the aggregate, have a Material Adverse Effect (as defined in
the Merger Agreement) on the Company and, to the extent consistent therewith,
use reasonable efforts to preserve intact their current business organizations,
keep available the services of their current officers and employees and preserve
their relationships with customers, suppliers, licensors, licensees,
distributors, designers, builders/dealers, contractors and others having
business dealings with them to the end that their goodwill and ongoing
businesses shall be unimpaired in any material respect at the Effective Time.
Without limiting the generality of the foregoing, without Parent's consent,
during the period from April 7, 1999 to the Effective Time, the Company has
agreed that it will not, and will not permit any of its subsidiaries to:
 
          (i) (w) declare, set aside or pay any dividends on, or make any other
     distributions in respect of, any of its capital stock or other equity
     interests, except for dividends by a direct or indirect wholly-owned
     subsidiary to its parent, (x) split, combine or reclassify any of its
     capital stock or other equity interests or issue or authorize the issuance
     of any other securities in respect of, in lieu of or in substitution for
     shares of its capital stock or other equity interests, (y) purchase, redeem
     or otherwise acquire any shares of its capital stock or capital stock or
     other equity interests of any of its subsidiaries or any other securities
     thereof or any rights, warrants or options to acquire any such shares,
     equity interests or other securities or (z) amend the terms of any
     outstanding capital stock of the Company or any of its subsidiaries or any
     other equity interests or securities thereof or any rights, warrants or
     options to acquire any such stock, equity interests or other securities;
 
          (ii) issue, deliver, sell, pledge or otherwise encumber any shares of
     its capital stock or other equity interests, any other voting securities or
     any securities convertible into, or any rights, warrants or options to
     acquire, any such shares, equity interests, voting securities or
     convertible securities (other than the issuance of Shares upon the exercise
     of Options outstanding on April 7, 1999 and in accordance with their
     present terms);
 
          (iii) amend its Certificate of Incorporation, By-laws or other
     comparable charter or organizational documents;
 
                                       27
<PAGE>   28
 
          (iv) acquire or agree to acquire (x) by merging or consolidating with,
     or by purchasing a substantial portion of the assets of, or by any other
     manner, any business or any corporation, partnership, joint venture,
     association or other business organization or division thereof or (y) any
     assets that are material, individually or in the aggregate, to the Company
     and its subsidiaries, except purchases in the ordinary course of business
     consistent with past practice;
 
          (v) sell, lease, license, mortgage or otherwise encumber or subject to
     any lien (other than liens pursuant to its existing credit facility) or
     otherwise dispose of any of its properties or assets which are material,
     individually or in the aggregate, to the Company and its subsidiaries,
     except sales in the ordinary course of business consistent with past
     practice;
 
          (vi) (y) incur, assume or prepay any indebtedness for borrowed money,
     including obligations in respect of capital leases (other than capital
     leases entered into with respect to capital expenditures permitted under
     clause (vii) below), or guarantee any such indebtedness of another person,
     issue or sell any debt securities or warrants or other rights to acquire
     any debt securities, or guarantee any debt securities of another person,
     except for borrowings under its revolving credit facility for working
     capital purposes, the endorsement of checks in the normal course of
     business and the extension of credit in the normal course of business, or
     (z) make any loans, advances or capital contributions to, or investments
     in, any other person, other than (A) to any direct or indirect wholly-owned
     subsidiary or (B) up to $800,000 of advances to American Buildings Company
     Asia, L.P. ("ABC Asia") for plant expansion and monthly advances for
     purchases of equipment and salary in accordance with past practice, which
     advances are reimbursed to the Company or (C) travel and similar advances
     to employees in accordance with past practice;
 
          (vii) except for the items currently contracted for by the Company and
     the items contemplated by the Company's 1999 capital expenditure budget
     made available to Parent, make or agree to make any new capital expenditure
     or expenditures other than expenditures which, in the aggregate, are not
     material in amount;
 
          (viii) make any material tax election or settle or compromise any
     material income tax liability;
 
          (ix) pay, discharge, settle or satisfy any claims, liabilities or
     obligations (absolute, accrued, asserted or unasserted, contingent or
     otherwise), other than the payment, discharge or satisfaction, in the
     ordinary course of business consistent with past practice or in accordance
     with their terms, of liabilities reflected or reserved against in, or
     contemplated by, the most recent consolidated financial statements (or the
     notes thereto) included in the reports, schedules, forms, statements and
     other documents filed by the Company with the Commission after December 31,
     1998 and publicly available prior to April 7, 1999, or incurred after
     December 31, 1998 in the ordinary course of business consistent with past
     practice, or waive any material benefits of, or agree to modify in any
     material respect, any confidentiality, standstill or similar agreements to
     which the Company or any of its subsidiaries is a party;
 
          (x) except in the ordinary course of business, modify, amend or
     terminate any Material Contract (as defined in the Merger Agreement) to
     which the Company or any of its subsidiaries is a party, or waive, release
     or assign any material rights or claims;
 
          (xi) except as required to comply with applicable law, (A) adopt,
     enter into, terminate or amend any Benefit Plans (as defined in the Merger
     Agreement), (B) increase in any manner the compensation or fringe benefits
     of, or pay any bonus to, any director, officer or employee (except for
     normal increases or bonuses in the ordinary course of business consistent
     with past practice, but specifically excluding the grant of any
     stock-related awards or compensation), (C) pay any benefit not provided for
     under any Benefit Plan, (D) except as permitted in clause (B) above, grant
     any awards under any bonus, incentive, performance or other compensation
     plan or arrangement or Benefit Plan (including the grant of stock options,
     stock appreciation rights, stock based or stock related awards, performance
     units or restricted stock, or remove existing restrictions in any Benefit
     Plans or agreement or awards made thereunder) or (E) take any action to
     fund or in any other way secure the payment of compensation or benefits
     under any employee plan, agreement, contract or arrangement or Benefit
     Plan;
 
                                       28
<PAGE>   29
 
          (xii) other than as required by law or generally accepted accounting
     principles, make any material change to its accounting policies or
     procedures;
 
          (xiii) make any investment in any person other than in readily
     marketable securities in an amount in excess of $100,000 in the aggregate
     whether by purchase of stock or securities, contributions to capital or any
     property transfer, or purchase for an amount in excess of $250,000 in the
     aggregate, any property or assets of any other individual or entity, other
     than investments in ABC Asia permitted by clause (vi) above;
 
          (xiv) except in the ordinary course of business consistent with past
     practice, license or permit any third party to use any intellectual
     property;
 
          (xv) waive or amend any term or condition of any confidentiality or
     "standstill" agreements to which the Company or any of its subsidiaries is
     a party;
 
          (xvi) settle or compromise any pending or threatened litigations
     without Purchaser's consent (which consent will not be unreasonably
     withheld or delayed), other than settlements of litigations which involve
     solely the payment of money not covered by insurance not to exceed $250,000
     in any one case or $500,000 in the aggregate;
 
          (xvii) permit any material insurance policy naming the Company or any
     subsidiary as a beneficiary or loss payable payee to be canceled or
     terminated; or
 
          (xviii) authorize any of, or commit or agree to take any of, the
     foregoing actions.
 
     No Solicitation.  The Merger Agreement provides that the Company shall not,
and shall not permit any of its subsidiaries to, and shall use its reasonable
best efforts to ensure that its officers, directors or employees or any
investment banker, attorney or other advisor or representative retained by it or
any of its subsidiaries do not, (i) solicit, initiate or encourage the
submission of, any Acquisition Proposal (as defined below), or (ii) participate
in any discussions or negotiations regarding, or furnish to any person any
information with respect to, or take any other action to facilitate any
inquiries or the making of any proposal that constitutes, or may reasonably be
expected to lead to, any Acquisition Proposal; provided, however, that prior to
the acceptance for payment of Shares pursuant to the Offer, to the extent
required by the fiduciary obligations of the Board, determined in good faith by
a majority of the disinterested members thereof (after consultation with the
Board's outside counsel and financial advisor), the Company may, in response to
an unsolicited Acquisition Proposal that, in the good faith determination by a
majority of the disinterested members of the Board (after consultation with the
Board's outside counsel and financial advisor), constitutes, or is reasonably
likely to lead to, a Superior Proposal (as defined below), furnish information
with respect to the Company to any third party pursuant to a customary
confidentiality agreement (which shall be no less favorable to the Company than
the Confidentiality Agreement) and discuss such information with such person and
participate in negotiations regarding such Superior Proposal. "Acquisition
Proposal" means any inquiry, proposal or offer from any third party relating to
any direct or indirect acquisition or purchase of a substantial amount of assets
of the Company or any of its subsidiaries, or more than a 20% interest in any
voting securities of the Company or any of its subsidiaries, or any tender offer
or exchange offer that if consummated would result in any person beneficially
owning 20% or more of any class of equity securities of the Company or any of
its subsidiaries, or any merger, consolidation, business combination, sale of
substantially all assets, recapitalization, liquidation, dissolution or similar
transaction involving the Company or any of its subsidiaries, other than the
transactions contemplated by the Merger Agreement. "Superior Proposal" means a
bona fide proposal made by a third party to acquire the Company pursuant to any
merger, sale of all or substantially all of the Company's assets, consolidation,
business combination, recapitalization, liquidation, dissolution or similar
transaction involving the Company or any transaction that would result in a
Change of Control (as defined below) that, in any case, the Board determines in
its good faith judgment (after consultation with the Board's outside counsel and
financial advisor) to be more favorable to the holders of Shares than the Merger
and for which any necessary financing is then committed. "Change of Control"
means any third party shall become the beneficial owner (within the meaning of
Rule 13d-3 under the Exchange Act) of 40% or more of the Company's outstanding
common stock.
 
                                       29
<PAGE>   30
 
     Pursuant to the Merger Agreement neither the Board nor any committee
thereof is permitted to (i) withdraw or modify, or propose to withdraw or
modify, in a manner adverse to Parent or Purchaser, the approval or
recommendation by the Board or any such committee of the Offer, the Merger
Agreement or the Merger, (ii) approve or recommend, or propose to approve or
recommend, any Acquisition Proposal or (iii) enter into any agreement with
respect to any Acquisition Proposal. Notwithstanding the foregoing, the Board,
to the extent required by the fiduciary obligations thereof, as determined in
good faith by a majority of the disinterested members thereof (after
consultation with the Board's outside counsel and financial advisor), may
(subject to the following limitations), (i) withdraw or modify its approval or
recommendation of the Offer, the Merger Agreement or the Merger, (ii) approve or
recommend any Superior Proposal or (iii) prior to any purchase by Purchaser of
Shares pursuant to the Offer upon satisfaction of the Minimum Condition,
provided the Company simultaneously terminates the Merger Agreement in
accordance with the terms of the Merger Agreement, cause the Company to enter
into a definitive agreement with respect to such Superior Proposal, in each case
provided that (x) a Superior Proposal has been made and not withdrawn and (y)
neither the Company nor any of its subsidiaries shall have violated certain
restrictions set forth in the Merger Agreement.
 
     Board of Directors; Officers.  The Merger Agreement provides that, promptly
upon the acceptance for payment of, and payment for, Shares by Purchaser
pursuant to the Offer, Purchaser shall be entitled to designate members of the
Board, as further described above under the caption "The Company's Board of
Directors." After the time that Purchaser's designees are elected to the Board
and until the Effective Time, any amendment or termination of the Merger
Agreement and any exercise or waiver of the Company's rights under the Merger
Agreement shall also require the approval of a majority of the Independent
Directors.
 
     Under the Merger Agreement, the directors of Purchaser immediately prior to
the Effective Time will be the initial directors of the Surviving Corporation,
and the officers of the Company immediately prior to the Effective Time will be
the initial officers of the Surviving Corporation, in each case until their
respective successors are duly elected or appointed and qualified.
 
     Access to Information.  Pursuant to the Merger Agreement, subject to the
Confidentiality Agreement, the Company shall, and shall cause each of its
subsidiaries to, afford to Parent, and to Parent's officers, employees,
accountants, counsel, financial advisors and other representatives, reasonable
access during normal business hours during the period prior to the Effective
Time to all their respective offices, properties, books, contracts, commitments,
personnel and records, provided that such access shall not interfere with the
normal business operations of the Company, and, during such period, the Company
shall, and shall cause each of its subsidiaries to, furnish promptly to Parent
(a) a copy of each report, schedule, registration statement and other document
filed by it during such period pursuant to the requirements of federal or state
securities laws and (b) all other information concerning its business,
properties and personnel as Parent may reasonably request.
 
     Employee Benefits Matters.  Under the Merger Agreement, for a period of at
least 18 months from the Effective Time, the Surviving Corporation will provide
pension, health and welfare benefits to employees of the Company and its
subsidiaries who continue their employment after the Effective Time which are
generally not less favorable in the aggregate to such continuing employees than
the benefits being provided to such continuing employees immediately prior to
the Effective Time. The Surviving Corporation will recognize the service of each
continuing employee through the Effective Time as if such service had been
performed with the Surviving Corporation for purposes of eligibility and vesting
under the Surviving Corporation's benefit plans.
 
     Directors' and Officers' Indemnification and Insurance.  The Merger
Agreement provides that the Company shall, to the fullest extent permitted by
Section 145 of the DGCL and regardless of whether the Merger becomes effective,
indemnify, defend and hold harmless, and after the Effective Time, Parent and
the Surviving Corporation shall, jointly and severally, to the fullest extent
permitted by Section 145 of the DGCL, indemnify, defend and hold harmless each
person who is, or has been at any time prior to the date hereof or who becomes
prior to the Effective Time, an officer or director of the Company or any of its
subsidiaries (collectively, the "Indemnified Parties" and individually, the
"Indemnified Party") against all losses,
 
                                       30
<PAGE>   31
 
liabilities, expenses, claims or damages in connection with any claim, suit,
action, proceeding or investigation based in whole or in part on the fact that
such Indemnified Party is or was a director or officer of the Company or any of
its subsidiaries and arising out of acts or omissions occurring prior to and
including the Effective Time (including but not limited to the transactions
contemplated by the Merger Agreement), for a period of not less than six years
following the Effective Time; provided, however, that in the event any claim or
claims are asserted or made within such six-year period, all rights to
indemnification in respect of any such claim or claims shall continue until
final disposition of any and all such claims.
 
     Under the Merger Agreement, Parent has agreed to cause the Certificate of
Incorporation and By-Laws of the Surviving Corporation and its subsidiaries to
include provisions for the limitation of liability of directors and
indemnification of the Indemnified Parties to the fullest extent permitted under
applicable law and not to permit the amendment of such provisions in any manner
adverse to the Indemnified Parties, as the case may be, without the prior
written consent of such persons, for a period of six years from and after the
date of the Merger Agreement. The Merger Agreement further provides that in the
event any such Indemnified Party is or becomes involved in any capacity in any
action, proceeding or investigation in connection with any matter, including,
without limitation, the transactions contemplated by the Merger Agreement,
occurring prior to, and including, the Effective Time, the Surviving Corporation
will pay as incurred such Indemnified Party's legal and other expenses
(including the cost of any investigation and preparation) incurred in connection
therewith, subject to the provision by such Indemnified Party of an undertaking
to reimburse such payments in the event of a final determination by a court of
competent jurisdiction that such Indemnified Party is not entitled thereto. The
Surviving Corporation is obligated to pay all expenses, including attorneys'
fees, that may be incurred by any Indemnified Party in enforcing the indemnity
and other obligations provided for in the Merger Agreement or any action
involving an Indemnified Party resulting from the transactions contemplated by
the Merger Agreement.
 
     In addition, the Merger Agreement provides that for six years after the
Effective Time, the Surviving Corporation shall cause to be maintained policies
of directors' and officers' liability insurance comparable to those currently
maintained by the Company for the benefit of directors and officers of the
Company (provided that the Surviving Corporation may substitute therefor
policies of at least the same coverage containing terms and conditions which are
substantially equivalent) with respect to matters occurring prior to the
Effective Time, provided that the Surviving Corporation is not obligated to
expend in any one year an amount in excess of 200% of the annual premiums
currently paid by the Company for such insurance (the Company has represented
that the annual premium is currently approximately $140,000), and provided
further, that if the annual premiums of such insurance coverage exceed such
amount, the Surviving Corporation is obligated to obtain a policy with the
greatest coverage available for a cost not exceeding such amount.
 
     The Merger Agreement further provides that in the event the Company or the
Surviving Corporation or any of their respective successors (i) is consolidated
with or merges into another person and shall not be the continuing or surviving
corporation or entity of such consolidation or merger or (ii) transfers all or
substantially all of its properties and assets to any person in a single
transaction or a series of transactions, then, and in each such case, Parent
shall make or cause to be made proper provision so that the successors or
transferees of the Company or the Surviving Corporation, as the case may be,
shall comply in all material respects with such indemnification and insurance
provisions.
 
     Representations and Warranties.  The Merger Agreement contains customary
representations and warranties with respect to the Company, including, without
limitation, (i) the Company's organization and capitalization, (ii) that the
Board of Directors of the Company has approved the Merger Agreement and the
transactions contemplated thereby (including the Offer and the Merger), (iii)
relating to required consents, approvals and governmental filings, (iv) the
accuracy of the Company's documents and reports filed with the Commission and
the Company's financial statements, (v) the absence of certain changes or events
which have had or would reasonably be expected to have, individually or in the
aggregate, a Material Adverse Effect, (vi) the absence of certain litigation,
(vii) the Company's employee benefit plans and other employment matters, (vii)
title to and condition of property, (viii) tax matters, (ix) environmental
matters, (x) intellectual property matters, (xi) insurance matters, (xii)
business relationships and restrictive agreements, (xiii) material contracts,
(xiv) product warranties and related matters and (xv) Year 2000 compliance.
                                       31
<PAGE>   32
 
     In the Merger Agreement, Parent and Purchaser have made customary
representations and warranties, including, without limitation, relating to their
respective corporate organization, authority to execute, deliver and perform the
Merger Agreement, and that Parent has available to it sufficient funds to
consummate the Offer and the Merger in accordance with the terms of the Merger
Agreement.
 
     Conditions to the Merger.  The respective obligations of each party to the
Merger Agreement to effect the Merger are subject to the satisfaction at or
prior to the Effective Time of the following conditions: (a) if required by the
DGCL, the Merger Agreement shall have been approved and adopted by the
affirmative vote of the holders of a majority of the outstanding Shares; (b) no
statute, rule or regulation shall have been enacted, promulgated or deemed
applicable to the Merger by any governmental entity which prevents the
consummation of the Merger or makes the consummation of the Merger unlawful, and
no temporary restraining order, preliminary or permanent injunction or other
order issued by any court of competent jurisdiction preventing the consummation
of the Merger shall be in effect, provided, however, that each of the parties is
obligated to use reasonable efforts to prevent the entry of any such injunction
or other order and to appeal as promptly as possible any injunction or other
order that may be entered; (c) all actions by or in respect of or filings with
any U.S. federal governmental entity required to permit the consummation of the
Merger shall have been completed; and (d) Purchaser shall have purchased all
Shares validly tendered and not withdrawn pursuant to the Offer, provided,
however, that this condition in clause (d) is not applicable to the obligations
of Parent or Purchaser if, in breach of the Merger Agreement or the terms of the
Offer, Purchaser fails to purchase any Shares validly tendered and not withdrawn
pursuant to the Offer.
 
     Termination.  The Merger Agreement may be terminated, and the Merger may be
abandoned, at any time prior to the Effective Time, whether before or after
approval of the Merger by the stockholders of the Company:
 
     (a) by mutual written consent of Parent, Purchaser and the Company (by
action of the Independent Directors only following the purchase of Shares
pursuant to the Offer);
 
     (b) by either Parent or the Company (by action of the Independent Directors
only following the purchase of Shares pursuant to the Offer): (i) if any court
or governmental entity shall have issued an order, decree or ruling or taken any
other action (which order, decree, ruling or other action the parties are
obligated to use their reasonable best efforts to lift) restraining, enjoining
or otherwise prohibiting the Merger and such order, decree, ruling or other
action shall have become final and nonappealable; or (ii) if (x) the Offer shall
have expired without any Shares being purchased therein or (y) Purchaser shall
not have accepted for payment all Shares tendered pursuant to the Offer by July
14, 1999; provided, however, that the right to terminate the Merger Agreement
pursuant to this clause (ii) shall not be available to any party whose failure
to fulfill any obligation under the Merger Agreement has been the cause of, or
resulted in, the failure of Purchaser to purchase the Shares pursuant to the
Offer on or prior to such date;
 
     (c) by the Company: (i) if Parent and/or Purchaser fails to commence the
Offer as provided in the Merger Agreement; provided, that the Company may not
terminate the Merger Agreement if the Company is at such time in breach of its
obligations under the Merger Agreement such as to (x) cause a Material Adverse
Effect on the Company or (y) prevent the purchase of Shares pursuant to the
Offer or the Merger; (ii) in connection with entering into a definitive
agreement with respect to a Superior Proposal, provided (x) that the Company has
notified Parent in writing of its intent to enter into such definitive agreement
at least three Business Days prior to the termination of the Merger Agreement,
and the relevant Acquisition Proposal continues to be a Superior Proposal
notwithstanding any modification by Parent and Purchaser of the terms of the
Offer and the Merger, (y) that the Company has complied with all relevant
provisions of the Merger Agreement including the notice provisions therein, and
(z) that the Company makes simultaneous payment of the Termination Fee (as
defined below); or (iii) if Parent or Purchaser shall have made a material
misrepresentation or have breached in any material respect any of their
respective representations, covenants or other agreements contained in the
Merger Agreement, which breach cannot be or has not been cured, in all material
respects, within 30 days after the giving of written notice to Parent or
Purchaser, as applicable; or
 
     (d) by Parent: (i) if, due to an occurrence, not involving a breach by
Parent or Purchaser of their obligations under the Merger Agreement, which makes
it impossible to satisfy any of the conditions set forth
                                       32
<PAGE>   33
 
in Section 15, Parent or Purchaser shall have failed to commence the Offer
within five Business Days of the initial public announcement of the Offer; (ii)
if, prior to the purchase of Shares pursuant to the Offer, the Company shall
have breached any representation, warranty, covenant or other agreement
contained in the Merger Agreement which (A) would give rise to the failure of a
condition set forth in paragraph (e) or (f) of Section 15 and (B) cannot be or
has not been cured, in all material respects, within 30 days after the giving of
written notice to the Company; or (iii) (A) if the Board shall have taken any
action pursuant to Section 6.02(b) of the Merger Agreement (including
withdrawing or modifying its approval or recommendation of the Offer, the Merger
or the Merger Agreement or approving or recommending an Acquisition Proposal) or
(B) the Company shall have entered into any definitive agreement with respect to
any Superior Proposal.
 
     In the event of the termination of the Merger Agreement and the abandonment
of the Offer and the Merger pursuant to the terms of the Merger Agreement, the
Merger Agreement shall, except as set forth therein, become void and have no
effect, without any liability on the part of any party thereto or its
affiliates, directors, officers or stockholders.
 
     Fees and Expenses.  Except as set forth below, all fees and expenses
incurred in connection with the Offer, the Merger, the Merger Agreement and the
transactions contemplated by the Merger Agreement shall be paid by the party
incurring such fees or expenses, whether or not the Offer or the Merger is
consummated.
 
     The Company is required to pay, or cause to be paid, to Onex a fee equal to
$8,000,000 (the "Termination Fee"), payable in immediately available funds prior
to or concurrently with termination of the Merger Agreement, if the Merger
Agreement is terminated (a) by the Company pursuant to clause (c)(ii) above
under "Termination," or (b) by Parent under clause (d)(iii) above under
"Termination" or (c) by any party for any reason (other than a material breach
of the Merger Agreement by Parent or Purchaser), provided in the case of this
clause (c) only (x) an Acquisition Proposal shall have been made by any third
party at any time on or after the date of the Merger Agreement and prior to such
termination, (y) the Minimum Condition is not satisfied and (z) there is (A) a
merger, sale of all or substantially all of the assets, consolidation, business
combination, recapitalization, liquidation, dissolution or similar transaction
involving the Company or a Change of Control, in any case within six months of
the date of termination of the Merger Agreement or (B) the Company enters into a
definitive agreement for any transaction referred to in clause (A) or a Change
of Control within six months of the date of termination of the Merger Agreement
and such transaction or Change of Control is subsequently consummated. If the
Termination Fee is payable to Onex for any reason, then the Company is also
required to reimburse Parent and its affiliates not later than two Business Days
after submission of reasonable documentation thereof for 100% of their
out-of-pocket fees and expenses (including the reasonable fees and expenses of
counsel), in each case, actually incurred by any of them or on their behalf in
connection with the Merger Agreement and the transactions contemplated thereby
(including the Merger and the arrangement of, obtaining the commitment to
provide or obtaining financing for the transactions contemplated by the Merger
Agreement (including fees payable to any financing parties and their respective
counsel)), up to a maximum reimbursement of $500,000.
 
     Amendments.  The Merger Agreement may be amended by the parties thereto at
any time before or after any required approval of the Merger by the stockholders
of the Company; provided, however, that after any such approval, there shall be
made no amendment that by law requires further approval by such stockholders
without the further approval of such stockholders. The Merger Agreement may not
be amended except by an instrument in writing signed on behalf of each of the
parties thereto.
 
     Conditions to the Offer.  The Merger Agreement provides for the Minimum
Condition and the other conditions to the Offer set forth in Section 15 of this
Offer to Purchase.
 
  THE LETTER OF UNDERTAKING
 
     Pursuant to the Letter of Undertaking, in consideration for and in order to
induce the Company to enter into the Merger Agreement, Onex has agreed to
provide or cause to be provided to Parent or Purchaser the funds necessary to
(i) purchase the Shares pursuant to the Offer and the Merger, (ii) pay all fees
and expenses related to the transactions contemplated by the Merger Agreement
and (iii) pay the liabilities or
                                       33
<PAGE>   34
 
obligations, if any, of Parent or Purchaser under Section 9.02 of the Merger
Agreement in the event of a termination of the Merger Agreement.
 
  THE CONFIDENTIALITY AGREEMENT
 
     Pursuant to the Confidentiality Agreement, Onex has agreed, among other
things, to keep confidential certain nonpublic confidential or proprietary
information of the Company furnished to Onex and its representatives by or on
behalf of the Company, including notes, analyses, compilations, studies,
interpretations or other documents prepared by Onex and its representatives
which contain, reflect or are based upon such information ("Evaluation
Material"), and to use the Evaluation Material solely for the purpose of
evaluating a possible transaction with the Company. Onex has further agreed to
maintain the confidentiality of any discussions or negotiations with the Company
and, upon request, to redeliver or destroy all the Evaluation Material. Onex
also agreed that, without the prior written consent of the Company, Onex will
not directly or indirectly enter into any agreement, arrangement or
understanding, or any discussions which might lead to an agreement, arrangement
or understanding, with any other person regarding a possible transaction
involving the Company for a period of two years from the date of the
Confidentiality Agreement. The Confidentiality Agreement further provides that,
for a period of two years from the date of the Confidentiality Agreement,
without the prior written consent of the Board, neither Onex nor any of its
affiliates, acting alone or as a part of a group, may acquire or offer to agree
to acquire, directly or indirectly, by purchase or otherwise, any voting
securities (or direct or indirect rights or options to acquire any voting
securities) of the Company, or otherwise seek to influence or control, in any
manner whatsoever, the management or policies of the Company. For a period of
two years from the date of the Confidentiality Agreement, neither Onex, nor any
of its affiliates will solicit to employ (whether as an employee, officer,
director, agent, consultant or independent contractor) any current officer or
employee of the Company and its subsidiaries with whom Onex had contact or who
was specifically identified to Onex during its investigation of the Company,
provided that Onex is permitted to hire any such person who responds to a
general advertisement not targeted at such person.
 
     Because Onex is an affiliate of Purchaser and Parent, the provisions of the
Confidentiality Agreement are also applicable to Purchaser and Parent.
 
     14.  DIVIDENDS AND DISTRIBUTIONS.  The Merger Agreement provides that from
April 7, 1999 through the Effective Time, the Company will not and will not
permit any of its subsidiaries to (i) declare, set aside or pay any dividends
on, or make any other distributions in respect of, any of its capital stock or
other equity interests, except for dividends by a direct or indirect wholly
owned subsidiary to its parent, (ii) split, combine or reclassify any of its
capital stock or other equity interests or issue or authorize the issuance of
any other securities in respect of, in lieu of or in substitution for shares of
its capital stock or other equity interests or (iii) purchase, redeem or
otherwise acquire any shares of its capital stock or capital stock or other
equity interests of any of its subsidiaries or any other securities thereof or
any rights, warrants or options to acquire any such shares, equity interests or
other securities.
 
     15.  CERTAIN CONDITIONS OF THE OFFER.  Notwithstanding any other term of
the Offer or the Merger Agreement, Purchaser is not required to accept for
payment or, subject to any applicable rules and regulations of the Commission,
including Rule 14e-1(c) under the Exchange Act (relating to Purchaser's
obligation to pay for or return tendered Shares after the termination or
withdrawal of the Offer), to pay for any Shares tendered pursuant to the Offer
unless (i) the Minimum Condition is satisfied and (ii) any waiting period under
the HSR Act applicable to the purchase of Shares pursuant to the Offer shall
have expired or been terminated. Furthermore, notwithstanding any other term of
the Offer or the Merger Agreement, Purchaser is not required to accept for
payment or, subject as aforesaid, to pay for any Shares not theretofore accepted
for payment or paid for, and may terminate the Offer if, at any time on or after
the date of the Merger Agreement and before the acceptance of such Shares for
payment or the payment therefor, any of the following conditions exists (other
than as a result of any action or inaction of Parent, Purchaser or any
subsidiary of Parent which constitutes a breach of the Merger Agreement):
 
          (a) there shall be threatened (with a reasonable likelihood of being
     brought) or pending by any governmental entity or by any other person any
     suit, action or proceeding (i) challenging or seeking to
 
                                       34
<PAGE>   35
 
     make illegal the acquisition by Parent or Purchaser of any Shares under the
     Offer, seeking to restrain or prohibit the making or consummation of the
     Offer or the Merger or seeking to obtain from the Company, Parent or
     Purchaser any damages that are material in relation to the Company and its
     subsidiaries taken as whole or seeking to impose any material adverse
     conditions in connection therewith, (ii) seeking to prohibit or limit the
     ownership or operation by the Company or any of its subsidiaries or Parent
     or Purchaser of a material portion of any material business or material
     assets of the Company and its subsidiaries, taken as a whole, or to compel
     the Company or Parent to dispose of or hold separate any material portion
     of any material business or material assets of the Company and its
     subsidiaries, taken as a whole, as a result of the Offer or the Merger,
     (iii) seeking to impose limitations on the ability of Parent or Purchaser
     to acquire or hold, or exercise full rights of ownership of, any Shares
     accepted for payment pursuant to the Offer including, without limitation,
     the right to vote such Shares on all matters properly presented to the
     stockholders of the Company, or (iv) seeking to prohibit Parent or
     Purchaser from effectively controlling in any material respect the business
     or operations of the Company and its subsidiaries, taken as a whole;
 
          (b) there shall be any statute, rule, regulation, judgment, order or
     injunction enacted, entered, enforced, promulgated or deemed applicable to
     the Offer or the Merger, or any other action shall be taken by any
     governmental entity, other than the application to the Offer or the Merger
     of applicable waiting periods under the HSR Act, that is reasonably likely
     to result, directly or indirectly, in any of the consequences referred to
     in clauses (i) through (iv) of paragraph (a) above;
 
          (c) there shall have occurred any events after April 7, 1999 which,
     individually or in the aggregate, have or are reasonably likely to have a
     Material Adverse Effect on the Company;
 
          (d) (i) the Company or the Board or any committee thereof shall have
     taken any action pursuant to Section 6.02(b) of the Merger Agreement or
     approved or recommended any Acquisition Proposal or (ii) the Company shall
     have entered into any definitive agreement for a Superior Proposal;
 
          (e) the representations and warranties of the Company set forth in the
     Merger Agreement (disregarding any qualification as to, or exception based
     on, materiality or Material Adverse Effect) shall not be true and correct
     (except for failures to be true and correct which would not, individually
     or in the aggregate, have a Material Adverse Effect) as of the date of the
     Merger Agreement and as if such representations and warranties were made at
     any time prior to the purchase of Shares pursuant to the Offer as if made
     at and as of such time;
 
          (f) the Company shall have (i) knowingly breached or failed to perform
     in any material respect any material obligation or to comply in any
     material respect with any material agreement or covenant of the Company to
     be performed or complied with by it under the Merger Agreement which is not
     cured within five days after notice from Purchaser or (ii) breached or
     failed to perform any obligation or to comply with any agreement or
     covenant of the Company to be performed or complied with by it under the
     Merger Agreement, which breach or failure in the case of this clause (ii)
     (x) has or is reasonably likely to have a Material Adverse Effect or (y)
     prevents the purchase of Shares pursuant to the Offer or the Merger;
 
          (g) the Merger Agreement shall have been terminated in accordance with
     its terms; or
 
          (h) there shall have occurred and be continuing (i) any general
     suspension of trading in securities on the New York, Toronto, or American
     Stock exchanges or in the Nasdaq National Market System (other than circuit
     breakers), (ii) the declaration of a banking moratorium or any suspension
     of payments in respect of banks in the United States or Canada, (iii) the
     commencement of a war, armed hostilities or other international or national
     calamity or emergency, directly or indirectly involving the United States
     or Canada (with the exception of any such occurrence involving Iraq or
     Yugoslavia), (iv) any limitations (whether or not mandatory) imposed by any
     governmental entity on the nature or extension of credit or further
     extension of credit by banks or other lending institutions or (v) a
     currency moratorium on the exchange markets in Canada or the United States
     with respect to the Canadian or United States dollar;
 
                                       35
<PAGE>   36
 
which, in the judgment of Purchaser in any case and regardless of circumstances,
makes it inadvisable to proceed with such acceptance for payment or payment.
 
     The foregoing conditions are for the sole benefit of Purchaser and Parent
and may, subject to the terms of the Merger Agreement, be waived by Purchaser
and Parent in whole or in part at any time and from time to time in their sole
discretion. The failure by Parent or Purchaser at any time to exercise any of
the foregoing rights shall not be deemed a waiver of any such right, the waiver
of any such right with respect to particular facts and circumstances shall not
be deemed a waiver with respect to any other facts and circumstances and each
such right shall be deemed an ongoing right that may be asserted at any time and
from time to time.
 
     16.  CERTAIN REGULATORY AND LEGAL MATTERS.
 
     General.  Except as set forth in this Section 16, Parent, Purchaser and
Onex are not aware of any approval or other action by any governmental or
administrative agency which would be required for the acquisition or ownership
of Shares by Purchaser as contemplated herein. Should any such approval or other
action be required, it will be sought, but Purchaser has no current intention to
delay the purchase of Shares tendered pursuant to the Offer pending the outcome
of any such matter, subject, however, to Purchaser's right to decline to
purchase Shares if any of the conditions specified in Section 15 shall have
occurred. There can be no assurance that any such approval or other action, if
needed, would be obtained or would be obtained without substantial conditions,
or that adverse consequences might not result to the Company's business or that
certain parts of the Company's business might not have to be disposed of if any
such approvals were not obtained or other action taken. If certain types of
adverse action are taken with respect to the matters discussed below, or certain
approvals, consents, licenses or permits identified below are not obtained,
Purchaser could decline to accept for payment or pay for any Shares tendered.
See Section 15.
 
     State Takeover Laws.  A number of states throughout the United States have
enacted takeover statutes that purport, in varying degrees, to be applicable to
attempts to acquire securities of corporations that are incorporated or have
assets, stockholders, executive offices or places of business in such states. In
Edgar v. MITE Corp., the Supreme Court of the United States held that the
Illinois Business Takeover Act, which involved state securities laws that made
the takeover of certain corporations more difficult, imposed a substantial
burden on interstate commerce and therefore was unconstitutional. In CTS Corp.
v. Dynamics Corp. of America, however, the Supreme Court of the United States
held that a state may, as a matter of corporate law and, in particular, those
laws concerning corporate governance, constitutionally disqualify a potential
acquirer from voting on the affairs of a target corporation without approval of
the remaining stockholders, provided that such laws were applicable only under
certain conditions.
 
     The Company is incorporated under the laws of the State of Delaware.
Section 203 of the DGCL generally prohibits such a Delaware corporation from
engaging in certain "business combinations" (defined to include mergers and
consolidations) with an "interested stockholder" (defined generally as any
person that beneficially owns 15% or more of the outstanding voting securities
of the corporation) for a period of three years after the date the person became
an interested stockholder unless, before such date, the board of directors of
the corporation approved either the business combination or the purchase of more
than 15% of the corporation's voting securities by the interested stockholder or
certain other statutory conditions have been met. On April 7, 1999, the Board
approved the purchase of Shares contemplated by the Offer and the Merger and any
purchase of Shares by Onex following the acquisition of Shares pursuant to the
Offer. Accordingly, Section 203 is inapplicable to, and will not prevent
consummation of, the Merger.
 
     Based on information supplied by the Company, Purchaser does not believe
that any other state takeover statutes purport to apply to the Offer or the
Merger. Neither Purchaser nor Parent has currently complied with any other state
takeover statute or regulation. Purchaser reserves the right to challenge the
applicability or validity of any state law purportedly applicable to the Offer
or the Merger, and nothing in this Offer to Purchase or any action taken in
connection with the Offer or the Merger is intended as a waiver of such right.
If it is asserted that any other state takeover statute is applicable to the
Offer or the Merger and an appropriate court does not determine that it is
inapplicable or invalid as applied to the Offer or the Merger, Purchaser might
be required to file certain information with, or to receive approvals from, the
relevant state authorities, and the Purchaser might be unable to accept for
payment or pay for securities tendered pursuant to the Offer,
                                       36
<PAGE>   37
 
or be delayed in consummating the Offer or the Merger. In such case, Purchaser
may not be obligated to accept for payment or pay for any securities tendered
pursuant to the Offer.
 
     Antitrust.  Under the provisions of the HSR Act applicable to the Offer,
the acquisition of Shares under the Offer may be consummated only following the
expiration or early termination of the applicable waiting period under the HSR
Act.
 
     Under the provisions of the HSR Act applicable to the purchase of Shares
pursuant to the Offer, such purchase may not be made until the expiration of a
15-calendar day waiting period following the required filing of a Notification
and Report Form under the HSR Act by Purchaser's ultimate parent. The Merger
Agreement requires that such form be filed as promptly as possible after the
date of the Merger Agreement and that early termination of the applicable
waiting period be requested. Accordingly, if the Notification and Report Form is
filed on April 13, 1999, the waiting period under the HSR Act would expire at
11:59 P.M., New York City time, on April 28, 1999, unless early termination of
the waiting period is granted by the Federal Trade Commission ("FTC") and the
Department of Justice, Antitrust Division (the "Antitrust Division") or a
request for additional information or documentary material is received prior
thereto. If either the FTC or the Antitrust Division issues a request for
additional information or documentary material from Purchaser prior to the
expiration of the 15-day waiting period, the waiting period will be extended and
will expire at 11:59 P.M., New York City time, on the tenth calendar day after
the date of substantial compliance by Purchaser's ultimate parent with such
request unless terminated earlier by the FTC and the Antitrust Division. If such
a request is issued, the purchase of and payment for Shares pursuant to the
Offer will be deferred until the additional waiting period expires or is
terminated. Only one extension of such waiting period pursuant to a request for
additional information or documentary material is authorized by the rules
promulgated under the HSR Act. Thereafter, the waiting period can be extended
only by court order or by consent of Purchaser's ultimate parent. Although the
Company is required to file certain information and documentary material with
the Antitrust Division and the FTC in connection with the Offer, neither the
Company's failure to make such filings nor a request to the Company from the
Antitrust Division or the FTC for additional information or documentary material
will extend the waiting period.
 
     The Antitrust Division and the FTC frequently scrutinize the legality under
the antitrust laws of transactions such as Purchaser's proposed acquisition of
the Company. At any time before or after Purchaser's purchase of Shares pursuant
to the Offer, the Antitrust Division or the FTC could take such action under the
antitrust laws as either deems necessary or desirable in the public interest,
including seeking to enjoin the purchase of Shares pursuant to the Offer or the
consummation of the Merger or seeking the divestiture of Shares acquired by
Purchaser or the divestiture of substantial assets of the Company or its
subsidiaries or Parent or its subsidiaries. Private parties and states'
Attorneys General may also bring legal action under the antitrust laws under
certain circumstances. If the Antitrust Division, the FTC, a state or a private
party raises antitrust concerns in connection with a proposed transaction, the
parties frequently engage in negotiations with the relevant governmental agency
concerning possible means of addressing these issues and may delay consummation
of the Offer or the Merger while such discussions are ongoing. There can be no
assurance that a challenge to the Offer on antitrust grounds will not be made,
or, if such a challenge is made, of the result thereof. See Section 15.
 
     17.  FEES AND EXPENSES.  Parent and Purchaser have retained Morrow & Co.,
Inc. to act as the Information Agent and American Stock Transfer & Trust Company
to act as the Depositary in connection with the Offer. The Information Agent and
the Depositary will each receive reasonable and customary compensation for their
services hereunder, be reimbursed for their reasonable out-of-pocket expenses
and be indemnified against certain liabilities and expenses in connection with
the Offer including certain liabilities under the securities laws.
 
     None of Parent, Purchaser or Onex, nor any officer, director, stockholder,
agent or other representative of Parent, Purchaser or Onex, will pay any fees or
commissions to any broker, dealer or other person (other than the Information
Agent) for soliciting tenders of Shares pursuant to the Offer. Brokers, dealers,
commercial banks and trust companies and other nominees will, upon request, be
reimbursed by the Purchaser for customary mailing and handling expenses incurred
by them in forwarding materials to their customers.
 
                                       37
<PAGE>   38
 
     18.  MISCELLANEOUS.  Purchaser is not aware of any state where the making
of the Offer is prohibited by administrative or judicial action pursuant to any
valid state statute. If Purchaser becomes aware of any valid state statute
prohibiting the making of the Offer or the acceptance of Shares pursuant
thereto, Purchaser will make a good faith effort to comply with such state
statute. If, after such good faith effort, Purchaser cannot comply with such
state statute, the Offer will not be made to (nor will tenders be accepted from
or on behalf of) the holders of Shares in such state. In any jurisdiction where
the securities, blue sky or other laws require the Offer to be made by a
licensed broker or dealer, the Offer shall be deemed to be made on behalf of
Purchaser by one or more registered brokers or dealers licensed under the laws
of such jurisdiction.
 
     NO PERSON HAS BEEN AUTHORIZED TO GIVE ANY INFORMATION OR MAKE ANY
REPRESENTATION ON BEHALF OF PURCHASER, PARENT OR ONEX OTHER THAN AS CONTAINED IN
THIS OFFER TO PURCHASE OR IN THE LETTER OF TRANSMITTAL, AND, IF ANY SUCH
INFORMATION OR REPRESENTATION IS GIVEN OR MADE, IT SHOULD NOT BE RELIED UPON AS
HAVING BEEN AUTHORIZED BY PURCHASER, PARENT OR ONEX.
 
     Purchaser, Parent and Onex have jointly filed a Tender Offer Statement on
Schedule 14D-1 with the Commission, pursuant to Rule 14d-1 of the Exchange Act,
together with exhibits furnishing certain information with respect to the Offer.
Such Schedule 14D-1 and any amendments thereto, including all exhibits, may be
examined and copies may be obtained at the same places and in the same manner as
set forth with respect to the Company in Section 8 (except that they may not be
available at the regional offices of the Commission).
 
                                          ABCO ACQUISITION CORP.
 
April 13, 1999
 
                                       38
<PAGE>   39
 
                                                                      SCHEDULE I
 
                 INFORMATION CONCERNING DIRECTORS AND EXECUTIVE
                     OFFICERS OF PARENT, PURCHASER AND ONEX
           AND PURCHASES OF COMPANY SHARES BY ONEX AND ITS AFFILIATES
 
     DIRECTORS AND EXECUTIVE OFFICERS OF PARENT AND PURCHASER.  The following
table sets forth the name and positions of each director and executive officer
of Parent and Purchaser. Each such person is a citizen of Canada and the
business address of each such person is c/o Onex Investment Corporation, 712
Fifth Avenue, 40th Floor, New York, New York 10019. The positions set forth
opposite each individual's name refer to positions with each of Parent and
Purchaser. The directors and executive officers of Parent and Purchaser have
held such positions since April 6, 1999.
 
<TABLE>
<CAPTION>
NAME                                                             POSITIONS
- ----                                                             ---------
<S>                                            <C>
Mark L. Hilson...............................  President, Treasurer and Director
Nigel S. Wright..............................  Vice President, Secretary and Director
</TABLE>
 
     Mr. Wright has been a principal of Onex since 1997. Prior to joining Onex,
Mr. Wright was a partner in the law firm of Davies, Ward & Beck in Ontario,
Canada for more than three years. Additional information about Mr. Hilson is set
forth in the table below under "Directors and Executive Officers of Onex
Corporation."
 
     DIRECTORS AND EXECUTIVE OFFICERS OF ONEX CORPORATION.  The following table
sets forth, for each director and executive officer of Onex, such person's name,
position with Onex, present principal occupation or employment and material
occupation, position, offices or employment for the past five years. Unless
otherwise indicated, each such person is a citizen of Canada and the business
address of each such person is c/o Onex Corporation, Canada Trust Tower, 161 Bay
Street, 49th Floor, Toronto, Ontario M5J2S1 Canada.
 
ONEX CORPORATION
 
<TABLE>
<CAPTION>
                                PRESENT PRINCIPAL OCCUPATION OR EMPLOYMENT/OTHER POSITIONS AND
NAME                            MATERIAL OCCUPATIONS OR POSITIONS HELD DURING PAST FIVE YEARS
- ----                            --------------------------------------------------------------
<S>                             <C>
Gerald W. Schwartz............  Chairman of the Board, President, Chief Executive Officer and
                                Director of Onex
 
Ewout R. Heersink
(Netherlands Citizen).........  Vice President and Chief Financial Officer of Onex
 
Mark L. Hilson................  Vice President of Onex
 
Anthony R. Melman.............  Vice President of Onex
 
Anthony Munk..................  Vice President of Onex
 
Seth M. Mersky
(U.S. Citizen)................  Vice President of Onex
 
John S. Elder, Q.C............  Secretary of Onex; Vice Chairman of the law firm of Fraser
                                Milner
                                Business Address: 1 First Canadian Place, 100 King Street West
                                Toronto, Ontario M5X 1B2 Canada
 
Dan C. Casey..................  Director of Onex; Chairman and Chief Executive Officer of
                                Creson Corporation, an Ontario real estate company
                                Business Address: Creson Corporation, 16 Clarence Square
                                Toronto, Ontario M5V 1H1 Canada
 
Donald H. Gales...............  Director of Onex
                                Business Address: Ellesmere Britannia, P.O. Box 1698GT,
                                Villa 639 Grand Cayman Island, British West Indies
 
Serge Gouin...................  Director of Onex; Vice Chairman of Salomon Smith Barney
                                Canada, Inc.
                                Business Address: Salomon Smith Barney, Canada, Inc. 1250
                                Rene-Levesque Boulevard, W. #2200 Montreal, Quebec, H3B 4W8
                                Canada
</TABLE>
 
                                       I-1
<PAGE>   40
 
<TABLE>
<CAPTION>
                                PRESENT PRINCIPAL OCCUPATION OR EMPLOYMENT/OTHER POSITIONS AND
NAME                            MATERIAL OCCUPATIONS OR POSITIONS HELD DURING PAST FIVE YEARS
- ----                            --------------------------------------------------------------
<S>                             <C>
Brian M. King.................  Director of Onex
                                Business Address: 13805 Ponderosa Way, Vernon,
                                British Colombia V1B 1A2 Canada
 
J. William E. Mingo, Q.C. ....  Director of Onex; Partner at Stewart McKelvey Stirling Scales,
                                a law firm in Halifax, Nova Scotia
                                Business Address: Stewart McKelvey Stirling Scales, 1959 Upper
                                Water St., 10th Floor, Halifax, Nova Scotia B3J2X2 Canada
 
J. Robert S. Prichard, O.C. ..  Director of Onex; President of the University of Toronto
                                Business Address: University of Toronto, 27 Kings College
                                Circle, Simcoe Hall, Room 206, Toronto, Ontario M5S 1A1 Canada
 
R. Geoffrey P. Styles.........  Director of Onex; Corporate Director of Royal Bank
                                Business Address: Royal Bank Plaza, Suite 3115, South Tower,
                                Toronto, Ontario M5J 2J5 Canada
 
Arni C. Thorsteinson..........  Director of Onex; President of Shelter Canadian Properties
                                Limited
                                Business Address: Shelter Canadian Properties Limited, 2600-7
                                Evergreen Place, Winnipeg, Manitoba R3L 2T3 Canada
</TABLE>
 
PURCHASES OF COMPANY SHARES BY ONEX AND ITS AFFILIATES
 
     A wholly-owned subsidiary of Onex (1306365 Ontario Inc.) purchased a total
of 255,000 Shares during the past 60 days, as follows:
 
<TABLE>
<CAPTION>
                                                              NUMBER OF    PRICE PER
                         TRADE DATE                            SHARES        SHARE
                         ----------                           ---------    ---------
<S>                                                           <C>          <C>
February 16, 1999...........................................    97,100      $21.80
February 17, 1999...........................................    85,600       21.69
February 23, 1999...........................................    17,200       20.67
February 24, 1999...........................................    25,100       20.63
February 26, 1999...........................................    30,000       20.59
                                                               -------
                                                               255,000
</TABLE>
 
     All of the transactions were effected through a registered broker-dealer on
the Nasdaq National Market. The total purchase price for the Shares, including
commissions, was $5,464,305.33.
 
                                       I-2
<PAGE>   41
 
                        The Depositary for the Offer is:
 
                    AMERICAN STOCK TRANSFER & TRUST COMPANY
                                 40 WALL STREET
                               NEW YORK, NY 10005
 
                             Facsimile Copy Number:
                                 (718) 234-5001
 
                             Confirm by Telephone:
                                 (718) 921-8200
 
                             For Information Call:
                                 (718) 921-8200
 
Any questions or requests for assistance or additional copies of the Offer to
Purchase and the related Letter of Transmittal, and other tender offer
materials, may be directed to the Information Agent at its telephone numbers and
address listed below. Stockholders may also contact their broker, dealer,
commercial bank, trust company or other nominee for assistance concerning the
Offer.
 
                    The Information Agent for the Offer is:
 
                               MORROW & CO., INC.
                           445 Park Avenue, 5th Floor
                            New York, New York 10022
                     Banks and Brokerage Firms Please Call:
                                 (800) 662-5200
 
                           Stockholders Please Call:
                                 (800) 566-9061

<PAGE>   1
 
                             LETTER OF TRANSMITTAL
                        TO TENDER SHARES OF COMMON STOCK
 
                                       OF
 
                           AMERICAN BUILDINGS COMPANY
 
             PURSUANT TO THE OFFER TO PURCHASE DATED APRIL 13, 1999
 
                                       OF
 
                             ABCO ACQUISITION CORP.
 
                     AN INDIRECT WHOLLY-OWNED SUBSIDIARY OF
                            [ONEX CORPORATION LOGO]
 
  THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY
          TIME, ON MONDAY, MAY 10, 1999, UNLESS THE OFFER IS EXTENDED.
 
                        The Depositary for the Offer is:
 
                            AMERICAN STOCK TRANSFER
                                & TRUST COMPANY
 
                             Facsimile Copy Number:
                                 (718) 234-5001
 
                             Confirm by Telephone:
                                 (718) 921-8200
 
                             For Information Call:
                                 (718) 921-8200
 
     By First Class Mail, by Express Mail or Overnight Courier, or by Hand:
 
                            American Stock Transfer
                                & Trust Company
                                 40 Wall Street
                                   46th Floor
                               New York, NY 10005
 
                            ------------------------
 
     DELIVERY OF THIS LETTER OF TRANSMITTAL TO AN ADDRESS OTHER THAN AS SET
FORTH ABOVE OR TRANSMISSION OF INSTRUCTIONS VIA A FACSIMILE NUMBER OTHER THAN AS
LISTED ABOVE WILL NOT CONSTITUTE A VALID DELIVERY. THE INSTRUCTIONS ACCOMPANYING
THIS LETTER OF TRANSMITTAL SHOULD BE READ CAREFULLY BEFORE THIS LETTER OF
TRANSMITTAL IS COMPLETED.
<PAGE>   2
 
     This Letter of Transmittal is to be completed by stockholders of American
Buildings Company (the "Company") if certificates representing Shares (as
defined below) are to be forwarded herewith or, unless an Agent's Message (as
defined in the Offer to Purchase) is utilized, if delivery of Shares is to be
made by book-entry transfer to the Depositary's account at The Depository Trust
Company (hereinafter referred to as the "Book-Entry Transfer Facility") pursuant
to the procedures set forth in Section 3 of the Offer to Purchase. Stockholders
whose stock certificates are not immediately available or who cannot deliver
their stock certificates and all other documents required hereby to the
Depositary prior to the Expiration Date (as defined in the Offer to Purchase),
or who cannot comply with the book-entry transfer procedures on a timely basis,
may nevertheless tender their Shares pursuant to the guaranteed delivery
procedure set forth in Section 3 of the Offer to Purchase. See Instruction 2.
DELIVERY OF DOCUMENTS TO THE BOOK-ENTRY TRANSFER FACILITY IN ACCORDANCE WITH THE
BOOK-ENTRY TRANSFER FACILITY'S PROCEDURES DOES NOT CONSTITUTE DELIVERY TO THE
DEPOSITARY.
 
[ ] CHECK HERE IF TENDERED SHARES ARE BEING DELIVERED BY BOOK-ENTRY TRANSFER TO
    THE DEPOSITARY'S ACCOUNT AT THE BOOK-ENTRY TRANSFER FACILITY AND COMPLETE
    THE FOLLOWING:
 
  Name of Tendering Institution:
  ------------------------------------------------------------------------------
 
  Account Number:
  ------------------------------------------------------------------------------
 
  Transaction Code Number:
  ------------------------------------------------------------------------------
 
[ ] CHECK HERE IF SHARES ARE BEING TENDERED PURSUANT TO A NOTICE OF GUARANTEED
    DELIVERY PREVIOUSLY SENT TO THE DEPOSITARY AND COMPLETE THE FOLLOWING:
 
   Name(s) of Registered Holder(s):
   -----------------------------------------------------------------------------
 
   Window Ticket No. (if any):
   -----------------------------------------------------------------------------
 
   Date of Execution of Notice of Guaranteed Delivery:
   -----------------------------------------------------------------
 
   Name of Institution which Guaranteed Delivery:
   ----------------------------------------------------------------------
 
<TABLE>
<CAPTION>
- ------------------------------------------------------------------------------------------------------------------------
                                             DESCRIPTION OF SHARES TENDERED
- ------------------------------------------------------------------------------------------------------------------------
      NAME(S) AND ADDRESS(ES) OF REGISTERED HOLDER(S)
       (PLEASE FILL IN, IF BLANK, EXACTLY AS NAME(S)                 STOCK CERTIFICATE(S) AND SHARE(S) TENDERED
             APPEAR(S) ON STOCK CERTIFICATE(S)                          (ATTACH ADDITIONAL LIST IF NECESSARY)
- ------------------------------------------------------------------------------------------------------------------------
                                                                                    TOTAL NUMBER
                                                                                      OF SHARES
                                                                    STOCK           EVIDENCED BY          NUMBER OF
                                                                 CERTIFICATE            STOCK              SHARES
                                                                NUMBER(S)(*)       CERTIFICATE(S)        TENDERED**
<S>                                                          <C>                 <C>                 <C>
                                                             ------------------------------------------------------
                                                             ------------------------------------------------------
                                                             ------------------------------------------------------
                                                             ------------------------------------------------------
                                                             ------------------------------------------------------
                                                                Total Shares
- ------------------------------------------------------------------------------------------------------------------------
  * Need not be completed by stockholders delivering Shares by book-entry transfer.
 ** Unless otherwise indicated, it will be assumed that all Shares evidenced by each stock certificate delivered to the
    Depositary are being tendered hereby. See Instruction 4.
- ------------------------------------------------------------------------------------------------------------------------
</TABLE>
 
     The name(s) and address(es) of the registered holder(s) should be printed,
if not already printed above, exactly as they appear on the certificate(s)
representing the Shares tendered hereby. The certificates and number of Shares
that the undersigned wishes to tender should be indicated in the appropriate
box.
 
                                        2
<PAGE>   3
 
                    NOTE: SIGNATURES MUST BE PROVIDED BELOW.
              PLEASE READ THE ACCOMPANYING INSTRUCTIONS CAREFULLY
 
LADIES AND GENTLEMEN:
 
     The undersigned hereby tenders to ABCO Acquisition Corp., a Delaware
corporation ("Purchaser"), a wholly-owned subsidiary of ABCO Holdings Corp., a
Delaware corporation and an indirect wholly-owned subsidiary of Onex
Corporation, an Ontario corporation, the above-described shares of Common Stock,
par value $.01 per share (the "Shares"), of American Buildings Company, a
Delaware corporation (the "Company"), pursuant to Purchaser's offer to purchase
all outstanding Shares at a purchase price of $36 per Share, net to the seller
in cash, without interest thereon, upon the terms and subject to the conditions
set forth in the Offer to Purchase, dated April 13, 1999 (the "Offer to
Purchase"), receipt of which is hereby acknowledged, and in this Letter of
Transmittal (which, together with the Offer to Purchase, as each may be amended
and supplemented from time to time, constitute the "Offer").
 
     Subject to, and effective upon, acceptance for payment of the Shares
tendered herewith, the undersigned hereby sells, assigns and transfers to or
upon the order of Purchaser all right, title and interest in and to all the
Shares that are being tendered hereby and any and all other Shares or other
securities issued or issuable in respect thereof on or after April 7, 1999 (each
a "Distribution") and appoints the Depositary the true and lawful agent and
attorney-in-fact of the undersigned with respect to such Shares (and any
Distributions), with full power of substitution (such power of attorney being
deemed to be an irrevocable power coupled with an interest), to (a) deliver
stock certificates (and any Distributions), or transfer ownership of such Shares
(and any Distributions) on the account books maintained by the Book-Entry
Transfer Facility, together, in any such case, with all accompanying evidences
of transfer and authenticity, to or upon the order of Purchaser, (b) present
such Shares (and any Distributions) for transfer on the books of the Company and
(c) receive all benefits and otherwise exercise all rights of beneficial
ownership of such Shares (and any Distributions), all in accordance with the
terms and subject to the conditions of the Offer.
 
     The undersigned hereby irrevocably appoints designees of Purchaser as the
attorneys and proxies of the undersigned, each with full power of substitution,
to exercise all voting and other rights of the undersigned in such manner as
each such attorney and proxy or his substitute shall in his sole judgment deem
proper, with respect to all of the Shares tendered hereby and any Distributions
which have been accepted for payment by Purchaser prior to the time of any vote
or other action at any meeting of stockholders of the Company (whether annual or
special and whether or not an adjourned meeting) or otherwise. This power of
attorney and proxy are irrevocable, are coupled with an interest in the Shares
tendered hereby and any Distributions, and are granted in consideration of, and
effective upon, the acceptance for payment of such Shares by Purchaser in
accordance with the terms of the Offer. Such acceptance for payment shall revoke
any other proxy or written consent granted by the undersigned at any time with
respect to such Shares (and any Distributions), and no subsequent proxies will
be given or written consents executed by the undersigned (and if given or
executed, will not be deemed effective).
 
     The undersigned hereby represents and warrants that the undersigned has
full power and authority to tender, sell, assign and transfer the Shares
tendered hereby (and any Distributions) and that when the same are accepted for
payment by Purchaser, Purchaser will acquire good and unencumbered title
thereto, free and clear of all liens, restrictions, charges and encumbrances and
not subject to any adverse claims. The undersigned will, upon request, execute
and deliver any additional documents deemed by the Depositary or Purchaser to be
necessary or desirable to complete the sale, assignment and transfer of the
Shares tendered hereby (and any Distributions). All authority herein conferred
or agreed to be conferred shall survive the death or incapacity of the
undersigned, and any obligation of the undersigned hereunder shall be binding
upon the heirs, personal representatives, successors and assigns of the
undersigned. Except as stated in the Offer, this tender is irrevocable.
 
     The undersigned understands that tenders of Shares pursuant to any one of
the procedures described in Section 3 of the Offer to Purchase and in the
instructions hereto will constitute an agreement between the undersigned and
Purchaser upon the terms and subject to the conditions of the Offer. The
undersigned recognizes that, under certain circumstances set forth in the Offer
to Purchase, Purchaser may not be required to accept for payment any of the
Shares tendered hereby. The undersigned acknowledges that no interest will be
paid on the purchase price for tendered Shares regardless of any extension of
the Offer or any delay in making such payment.
 
                                        3
<PAGE>   4
 
     Unless otherwise indicated in the box entitled "Special Payment
Instructions," please issue the check for the purchase price of any Shares
purchased, and return any stock certificates evidencing any Shares not tendered
or not purchased, in the name(s) of the undersigned (and, in the case of Shares
tendered by book-entry transfer, by credit to the account at the Book-Entry
Transfer Facility). Similarly, unless otherwise indicated in the box entitled
"Special Delivery Instructions," please mail the check for the purchase price of
any Shares purchased and return any stock certificates evidencing any Shares not
tendered or not purchased (and accompanying documents, as appropriate) to the
undersigned at the address shown below the undersigned's signature(s). In the
event that the boxes entitled "Special Payment Instructions" and "Special
Delivery Instructions" are both completed, please issue the check for the
purchase price of any Shares purchased and return any stock certificates
evidencing any Shares not tendered or not purchased in the name(s) of, and mail
said check and stock certificates to, the person(s) so indicated. Stockholders
tendering Shares by book-entry transfer may request that any Shares not accepted
for payment be returned by crediting such account maintained at the Book-Entry
Transfer Facility as such stockholder may designate by making an appropriate
entry under "Special Payment Instructions." The undersigned acknowledges that
Purchaser has no obligation, pursuant to the "Special Payment Instructions," to
transfer any Shares from the name of the registered holder(s) thereof if
Purchaser does not accept for payment any of the Shares so tendered.
 
          ------------------------------------------------------------
 
                          SPECIAL PAYMENT INSTRUCTIONS
                        (SEE INSTRUCTIONS 1, 5, 6 AND 7)
 
        To be completed ONLY if the check for the purchase price of Shares
   purchased or stock certificates evidencing Shares not tendered or not
   purchased are to be issued in the name of someone other than the
   undersigned, or if Shares tendered hereby and delivered by book-entry
   transfer which are not purchased are to be returned by credit to an
   account at a Book-Entry Transfer Facility other than that designated
   above.
 
   Issue:  [ ] Check  [ ] Stock Certificate(s) to:
 
   Name
   ----------------------------------------------------
                                    (PLEASE PRINT)
 
   Address
   --------------------------------------------------
 
          ------------------------------------------------------------
 
          ------------------------------------------------------------
                                   (ZIP CODE)
 
          ------------------------------------------------------------
                (TAXPAYER IDENTIFICATION OR SOCIAL SECURITY NO.)
                   (SEE SUBSTITUTE FORM W-9 ON REVERSE SIDE)
 
   [ ] Credit Shares delivered by book-entry transfer and not purchased to
       the account set forth below:
 
          ------------------------------------------------------------
                                (ACCOUNT NUMBER)
          ------------------------------------------------------------
          ------------------------------------------------------------
 
                         SPECIAL DELIVERY INSTRUCTIONS
                        (SEE INSTRUCTIONS 1, 5, 6 AND 7)
 
        To be completed ONLY if the check for the purchase price of Shares
   purchased or stock certificates evidencing Shares not tendered or not
   purchased are to be mailed to someone other than the undersigned, or to
   the undersigned at an address other than that shown under the
   undersigned's signature.
 
   Mail:  [ ] Check  [ ] Stock certificate(s) to:
 
   Name
   ----------------------------------------------------
                                    (PLEASE PRINT)
 
   Address
   --------------------------------------------------
 
          ------------------------------------------------------------
 
          ------------------------------------------------------------
                                   (ZIP CODE)
 
          ------------------------------------------------------------
                (TAXPAYER IDENTIFICATION OR SOCIAL SECURITY NO.)
                   (SEE SUBSTITUTE FORM W-9 ON REVERSE SIDE)
 
          ------------------------------------------------------------
 
                                        4
<PAGE>   5
 
                                   IMPORTANT
                            STOCKHOLDERS: SIGN HERE
             (PLEASE COMPLETE SUBSTITUTE FORM W-9 ON REVERSE SIDE)
(Signature(s) of Holder(s))
- --------------------------------------------------------------------------------
 
- --------------------------------------------------------------------------------
 
Dated:
- --------------------------- , 1999
 
(Must be signed by registered holder(s) exactly as name(s) appear(s) on stock
certificate(s) or on a security position listing or by person(s) authorized to
become registered holder(s) by certificates and documents transmitted herewith.
If signature is by a trustee, executor, administrator, guardian,
attorney-in-fact, officer of a corporation or other person acting in a fiduciary
or representative capacity, please provide the following information and see
Instruction 5.)
 
Name(s):
       -------------------------------------------------------------------------
 
- --------------------------------------------------------------------------------
                                 (PLEASE PRINT)
 
Capacity (full title):
               -----------------------------------------------------------------
 
Address:
       -------------------------------------------------------------------------
 
- --------------------------------------------------------------------------------
                               (INCLUDE ZIP CODE)
 
Area Code and Telephone No.:
                       ---------------------------------------------------------
 
Taxpayer Identification or Social Security No.:
                                  ----------------------------------------------
 
                           GUARANTEE OF SIGNATURE(S)
                           (SEE INSTRUCTIONS 1 AND 5)
                    FOR USE BY FINANCIAL INSTITUTIONS ONLY.
                    PLACE MEDALLION GUARANTEE IN SPACE BELOW
 
Authorized Signature:
                ----------------------------------------------------------------
 
Name: --------------------------------------------------------------------------
 
- --------------------------------------------------------------------------------
                             (PLEASE TYPE OR PRINT)
 
Title:
     ---------------------------------------------------------------------------
 
Name of Firm:
           ---------------------------------------------------------------------
 
Address:
       -------------------------------------------------------------------------
 
Area Code and Telephone No.:
                       ---------------------------------------------------------
 
Dated:
- --------------------------- , 1999
 
                                        5
<PAGE>   6
 
                                  INSTRUCTIONS
 
             Forming Part of the Terms and Conditions of the Offer
 
     1.  GUARANTEE OF SIGNATURES.  Except as otherwise provided below,
signatures on this Letter of Transmittal must be guaranteed by a firm that is a
bank, broker, dealer, credit union, savings association or other entity which is
a member in good standing of the Securities Transfer Agents Medallion Program or
by any other bank, broker, dealer, credit union, savings association or other
entity which is an "eligible guarantor institution," as such term is defined in
Rule 17Ad-15 under the Securities Exchange Act of 1934, as amended (each of the
foregoing constituting an "Eligible Institution"), unless the Shares tendered
thereby are tendered (i) by the registered holder(s) of such Shares who has not
completed either the box labeled "Special Payment Instructions" or the box
labeled "Special Delivery Instructions" on this Letter of Transmittal or (ii)
for the account of an Eligible Institution. See Instruction 5. If stock
certificates are registered in the name of a person or persons other than the
signer of this Letter of Transmittal, or if payment is to be made or delivered
to, or certificates evidencing unpurchased Shares are to be issued or returned
to, a person other than the registered owner or owners, then the tendered stock
certificates must be endorsed or accompanied by duly executed stock powers, in
either case signed exactly as the name or names of the registered owner or
owners appear on the stock certificates, with the signatures on the stock
certificates or stock powers guaranteed by an Eligible Institution as provided
herein. See Instruction 5.
 
     2.  DELIVERY OF LETTER OF TRANSMITTAL AND STOCK CERTIFICATES.  This Letter
of Transmittal is to be used either if stock certificates are to be forwarded
herewith or, unless an Agent's Message (as defined in the Offer to Purchase) is
utilized, if the delivery of Shares is to be made by book-entry transfer
pursuant to the procedures set forth in Section 3 of the Offer to Purchase.
Certificates for all physically delivered Shares, or a confirmation of a
book-entry transfer into the Depositary's account at the Book-Entry Transfer
Facility of all Shares delivered electronically, as well as a properly completed
and duly executed Letter of Transmittal (or a manually signed facsimile
thereof), or an Agent's Message in the case of a book-entry transfer, and any
other documents required by this Letter of Transmittal must be received by the
Depositary at one of its addresses set forth on the front page of this Letter of
Transmittal by the Expiration Date (as defined in the Offer to Purchase).
Stockholders who cannot deliver their stock certificates and all other required
documents to the Depositary by the Expiration Date must tender their Shares
pursuant to the guaranteed delivery procedure set forth in Section 3 of the
Offer to Purchase. Pursuant to such procedure: (a) such tender must be made by
or through an Eligible Institution; (b) a properly completed and duly executed
Notice of Guaranteed Delivery, substantially in the form provided by Purchaser,
must be received by the Depositary prior to the Expiration Date; and (c) the
stock certificates for all tendered Shares, in proper form for tender, or a
confirmation of a book-entry transfer into the Depositary's account at the Book-
Entry Transfer Facility of all Shares delivered electronically, as well as a
properly completed and duly executed Letter of Transmittal (or a manually signed
facsimile thereof), or an Agent's Message in the case of a book-entry transfer,
and any other documents required by this Letter of Transmittal, must be received
by the Depositary within three trading days (as defined in Section 3 of the
Offer to Purchase) after the date of execution of such Notice of Guaranteed
Delivery, all as provided in Section 3 of the Offer to Purchase.
 
     THE METHOD OF DELIVERY OF THIS LETTER OF TRANSMITTAL, STOCK CERTIFICATES
AND ALL OTHER REQUIRED DOCUMENTS, INCLUDING DELIVERY THROUGH ANY BOOK-ENTRY
TRANSFER FACILITY, IS AT THE OPTION AND RISK OF THE TENDERING STOCKHOLDER, AND
THE DELIVERY WILL BE DEEMED MADE ONLY WHEN ACTUALLY RECEIVED BY THE DEPOSITARY.
IF DELIVERY IS BY MAIL, REGISTERED MAIL WITH RETURN RECEIPT REQUESTED, PROPERLY
INSURED, IS RECOMMENDED. IN ALL CASES, SUFFICIENT TIME SHOULD BE ALLOWED TO
ENSURE TIMELY DELIVERY.
 
     No alternative, conditional or contingent tenders will be accepted. By
execution of this Letter of Transmittal (or a manually signed facsimile
thereof), all tendering stockholders waive any right to receive any notice of
the acceptance of their Shares for payment.
 
     3.  INADEQUATE SPACE.  If the space provided herein is inadequate, the
stock certificate numbers and/or the number of Shares should be listed on a
separate schedule attached hereto.
 
     4.  PARTIAL TENDERS (NOT APPLICABLE TO STOCKHOLDERS WHO TENDER BY
BOOK-ENTRY TRANSFER).  If fewer than all the Shares represented by any stock
certificate delivered to the Depositary are to be tendered, fill in the number
of Shares which are to be tendered in the box entitled "Number of Shares
Tendered." In such case, a new stock certificate for the remainder of the Shares
represented by the old stock certificate will be sent to the person(s) signing
this Letter of
 
                                        6
<PAGE>   7
 
Transmittal, unless otherwise provided in the box entitled "Special Payment
Instructions" or "Special Delivery Instructions," as promptly as practicable
following the expiration or termination of the Offer. All Shares represented by
stock certificates delivered to the Depositary will be deemed to have been
tendered unless otherwise indicated.
 
     5.  SIGNATURES ON LETTER OF TRANSMITTAL; STOCK POWERS AND ENDORSEMENTS.  If
this Letter of Transmittal is signed by the registered holder(s) of the Shares
tendered hereby, the signature(s) must correspond with the name(s) as written on
the face of the stock certificates without alteration, enlargement or any other
change whatsoever.
 
     If any of the Shares tendered hereby are owned of record by two or more
persons, all such persons must sign this Letter of Transmittal.
 
     If any of the Shares tendered hereby are registered in different names on
different stock certificates, it will be necessary to complete, sign and submit
as many separate Letters of Transmittal as there are different registrations of
stock certificates.
 
     If this Letter of Transmittal is signed by the registered holder(s) of the
Shares tendered hereby, no endorsements of stock certificate(s) or separate
stock powers are required, unless payment of the purchase price is to be made
to, or stock certificate(s) evidencing Shares not tendered or not purchased are
to be returned to or issued in the name of, any person other than the registered
holder(s). Signatures on any such stock certificates or stock powers must be
guaranteed by an Eligible Institution.
 
     If this Letter of Transmittal is signed by a person other than the
registered holder(s) of the Shares tendered hereby, the stock certificate(s)
evidencing the Shares tendered hereby must be endorsed or accompanied by
appropriate stock powers, in either case signed exactly as the name(s) of the
registered holder(s) appear(s) on such stock certificate(s). Signature(s) on any
such stock certificate(s) or stock powers must be guaranteed by an Eligible
Institution.
 
     If this Letter of Transmittal or any stock certificate or stock power is
signed by a trustee, executor, administrator, guardian, attorney-in-fact,
officer of a corporation or other person acting in a fiduciary or representative
capacity, such person should so indicate when signing and proper evidence
satisfactory to Purchaser of the authority of such person so to act must be
submitted.
 
     6.  STOCK TRANSFER TAXES.  Purchaser will pay any stock transfer taxes with
respect to the sale and transfer of any Shares to it or its order pursuant to
the Offer. If, however, payment of the purchase price is to be made to, or stock
certificates evidencing Shares not tendered or not purchased are to be returned
to, or issued in the name of, any person other than the registered holder(s) of
such Shares, then the amount of any stock transfer taxes (whether imposed on the
registered holder(s), such other person or otherwise) payable on account of the
transfer to such person will be deducted from the purchase price unless
satisfactory evidence of the payment of such taxes, or exemption therefrom, is
submitted. EXCEPT AS PROVIDED IN THIS INSTRUCTION 6, IT WILL NOT BE NECESSARY
FOR TRANSFER TAX STAMPS TO BE AFFIXED TO THE STOCK CERTIFICATE(S) LISTED IN THIS
LETTER OF TRANSMITTAL.
 
     7.  SPECIAL PAYMENT AND DELIVERY INSTRUCTIONS.  If the check for the
purchase price of any Shares purchased is to be issued, or any stock
certificates evidencing Shares not tendered or not purchased are to be returned,
in the name of a person other than the person(s) signing this Letter of
Transmittal or if the check or any stock certificates evidencing Shares not
tendered or not purchased are to be mailed to someone other than the person(s)
signing this Letter of Transmittal or to the person(s) signing this Letter of
Transmittal at an address other than that shown above, the appropriate boxes on
this Letter of Transmittal should be completed. Stockholders tendering Shares by
book-entry transfer may request that Shares not purchased be credited to such
account at the Book-Entry Transfer Facility as such stockholder may designate in
the box entitled "Special Payment Instructions." If no such instructions are
given, any such Shares not purchased will be returned by crediting the account
at the Book-Entry Transfer Facility.
 
     8.  LOST, DESTROYED OR STOLEN CERTIFICATES.  If any certificate(s)
representing Shares has been lost, or stolen, the stockholder should promptly
notify the Depositary. The stockholder will then be instructed as to the steps
that must be taken in order to replace the certificate(s). This Letter of
Transmittal and related documents cannot be processed until the procedures for
replacing lost or destroyed certificates have been followed.
 
                                        7
<PAGE>   8
 
     9.  WAIVER OF CONDITIONS.  Except in certain circumstances where the
Company's consent is required, in the case of any Shares tendered hereby the
conditions of the Offer may be waived by Purchaser, in whole or in part, at any
time and from time to time in Purchaser's sole discretion.
 
     10.  SUBSTITUTE FORM W-9.  The tendering holder of Shares is required to
provide the Depositary with such holder's correct taxpayer identification number
("TIN") on Substitute Form W-9, which is provided below, unless an exemption
applies. In the case of such a holder who has completed the box entitled
"Special Payment Instructions," however, the correct TIN on Substitute Form W-9
should be provided for the recipient of the payment pursuant to such
instructions. Failure to provide the information on the Substitute Form W-9 may
subject the tendering holder of Shares to a $50 penalty and to 31% federal
income tax backup withholding on the payment of the purchase price for the
Shares.
 
     11.  FOREIGN HOLDERS.  Foreign holders must submit a completed IRS Form W-8
to avoid backup withholding. IRS Form W-8 may be obtained by contacting the
Depositary at one of the addresses on the face of this Letter of Transmittal.
 
     12.  QUESTIONS AND REQUESTS FOR ASSISTANCE OR ADDITIONAL COPIES.  Questions
and requests for assistance may be directed to the Information Agent at its
address and telephone numbers set forth on the back cover of the Offer to
Purchase. Additional copies of the Offer to Purchase, the Letter of Transmittal,
the Notice of Guaranteed Delivery and other related materials may be obtained
from the Information Agent or from brokers, dealers, commercial banks and trust
companies.
 
     THIS LETTER OF TRANSMITTAL (OR A MANUALLY SIGNED FACSIMILE COPY HEREOF), OR
AN AGENT'S MESSAGE IN THE CASE OF A BOOK-ENTRY TRANSFER, TOGETHER WITH STOCK
CERTIFICATES OR CONFIRMATION OF BOOK-ENTRY TRANSFER AND ALL OTHER REQUIRED
DOCUMENTS, OR NOTICE OF GUARANTEED DELIVERY MUST BE RECEIVED BY THE DEPOSITARY
ON OR PRIOR TO THE EXPIRATION DATE.
 
                                        8
<PAGE>   9
 
                           IMPORTANT TAX INFORMATION
 
     Under the federal income tax law, a holder of Shares whose tendered Shares
are accepted for payment is required by law to provide the Depositary (as payor)
with such holder's correct TIN on Substitute Form W-9 below. The holder of
Shares must also state that (i) such holder has not been notified by the
Internal Revenue Service that such holder is subject to backup withholding as a
result of a failure to report all interest or dividends or (ii) the Internal
Revenue Service has notified such holder that such holder is no longer subject
to backup withholding. If the Depositary is not provided with the correct TIN,
the holder of Shares may be subject to a $50 penalty imposed by the Internal
Revenue Service and payments made to such holder may be subject to backup
withholding.
 
     Certain holders of Shares (including, among others, all corporations and
certain foreign individuals) are not subject to these backup withholding and
reporting requirements. In order for a foreign individual to qualify as an
exempt recipient, such individual must submit a statement, signed under
penalties of perjury, attesting to such individual's exempt status. Forms of
such statements can be obtained from the Depositary. See the enclosed Guidelines
for Certification of Taxpayer Identification Number on Substitute Form W-9 for
additional instructions.
 
     If backup withholding applies, the Depositary is required to withhold 31%
of any payments made to the holder of Shares. Backup withholding is not an
additional tax. Rather, the tax withheld pursuant to backup withholding rules
will be available as a credit against such holder's tax liabilities. If
withholding results in an overpayment of taxes, a refund may be obtained from
the Internal Revenue Service.
 
PURPOSE OF SUBSTITUTE FORM W-9
 
     To prevent backup withholding on payments that are made to a stockholder
with respect to Shares purchased pursuant to the Offer, the stockholder is
required to notify the Depositary of such stockholder's correct TIN by
completing the Substitute Form W-9 below certifying that the TIN provided on
such form is correct (or that such stockholder is awaiting a TIN) and that (i)
such holder is exempt from backup withholding, (ii) such holder has not been
notified by the IRS that such holder is subject to backup withholding as a
result of a failure to report all interest or dividends, or (iii) the IRS has
notified such holder that such holder is no longer subject to backup withholding
(see Part 2 of Substitute Form W-9).
 
WHAT NUMBER TO GIVE THE DEPOSITARY
 
     If the holder of Shares is an individual, the correct TIN is his or her
social security number. In other cases, the correct TIN may be the employer
identification number of the record holder of the Shares tendered hereby. If the
Shares are in more than one name or are not in the name of the actual owner,
consult the enclosed Guidelines for Certification of Taxpayer Identification
Number on Substitute Form W-9 for additional guidance on which number to report.
If the tendering holder of Shares has not been issued a TIN and has applied for
a number or intends to apply for a number in the near future, the holder should
write "Applied For" in the space provided for the TIN in Part I of the
Substitute Form W-9, and sign and date the Substitute Form W-9. If "Applied For"
is written in Part I of the Substitute Form W-9 and the Depositary is not
provided with a TIN within 30 days, the Depositary may withhold 31% of all
payments of the purchase price to such holder until a TIN is provided to the
Depositary.
 
                                        9
<PAGE>   10
 
<TABLE>
<S>                          <C>                                                         <C>
- ------------------------------------------------------------------------------------------------------------------------
                                 PAYOR'S NAME: AMERICAN STOCK TRANSFER & TRUST COMPANY
- ------------------------------------------------------------------------------------------------------------------------
  SUBSTITUTE                   PART I--Taxpayer Identification Number. For all                     PART III--
  FORMW-9                      accounts, enter taxpayer identification number in the         -----------------------
                               box at right. (For most individuals, this is your social      SOCIAL SECURITY NUMBER
                               security number. If you do not have a number, see           OR ------------------------
                               OBTAINING A NUMBER in the enclosed Guidelines.) Certify   EMPLOYER IDENTIFICATION NUMBER
                               by signing and dating below. NOTE: If the account is in          (IF AWAITING TIN
                               more than one name, see chart in the enclosed Guidelines       WRITE "APPLIED FOR")
                               to determine which number to give the payor.
                             -------------------------------------------------------------------------------------------
 
 Department of the
  Treasury, Internal           PART II--For Payees exempt from backup withholding, see the enclosed Guidelines and
  Revenue Service              complete as instructed therein.
  PAYOR'S REQUEST FOR
  TAXPAYER IDENTIFICATION      -----------------------------------------------------------------------------------------
      NUMBER ("TIN")           CERTIFICATION -- UNDER PENALTIES OF PERJURY, I CERTIFY THAT:
                               (1) The number shown on this form is my correct Taxpayer Identification Number (or I am
                                   waiting for a number to be issued to me); and
                               (2) I am not subject to backup withholding either because (a) I have not been notified by
                                   the Internal Revenue Service (IRS) that I am subject to backup withholding as a
                                   result of a failure to report all interest or dividends, or (b) the IRS has notified
                                   me that I am no longer subject to backup withholding.
- ------------------------------------------------------------------------------------------------------------------------
 
   CERTIFICATION INSTRUCTIONS--You must cross out item (2) above if you have been notified by the IRS that
   you are subject to backup withholding because of underreporting interest or dividends on your tax return. However, if
   after being notified by the IRS that you were subject to backup withholding, you received another notification from
   the IRS that you were no longer subject to backup withholding, do not cross out item (2). (Also see instructions in
   the enclosed Guidelines.)
   SIGNATURE:
- ------------------------------------------------------------------------------------------------------------------------
   DATE:
- ------------------------------------------------------------------------------------------------------------------------
   NAME:
- ------------------------------------------------------------------------------------------------------------------------
   ADDRESS:
- ------------------------------------------------------------------------------------------------------------------------
   CITY-STATE-ZIP:
- ------------------------------------------------------------------------------------------------------------------------
- ------------------------------------------------------------------------------------------------------------------------
</TABLE>
 
NOTE:  FAILURE TO COMPLETE AND RETURN THE SUBSTITUTE FORM W-9 MAY RESULT IN
       BACKUP WITHHOLDING OF 31% OF ANY PAYMENTS MADE TO YOU PURSUANT TO THE
       OFFER TO PURCHASE. PLEASE REVIEW THE ENCLOSED GUIDELINES FOR
       CERTIFICATION OF TAXPAYER IDENTIFICATION NUMBER ON SUBSTITUTE FORM W-9
       FOR ADDITIONAL DETAILS.
 
       YOU MUST COMPLETE THE FOLLOWING CERTIFICATE IF YOU ARE AWAITING (OR WILL
       SOON APPLY FOR) A TAXPAYER IDENTIFICATION NUMBER.
 
<TABLE>
<S>                                                                <C>
- --------------------------------------------------------------------------------------------------
                      CERTIFICATE OF AWAITING TAXPAYER IDENTIFICATION NUMBER
 
 I certify under penalties of perjury that a taxpayer identification number has not been issued to
 me, and either (a) I have mailed or delivered an application to receive a taxpayer identification
 number to the appropriate Internal Revenue Service Center or Social Security Administration
 Office or (b) I intend to mail or deliver an application in the near future. I understand that,
 notwithstanding the information I provided in Part III of the Substitute Form W-9 (and the fact
 that I have completed this Certificate of Awaiting Taxpayer Identification Number), if I do not
 provide a correct TIN to the Depositary within 30 days, 31% of all reportable payments made to me
 pursuant to the Offer may be withheld.
  Signature: ______________________________________________________ Date: ---------------------
- --------------------------------------------------------------------------------------------------
</TABLE>
 
     If you have any questions regarding the Offer, please contact the
Information Agent.
 
                                       10
<PAGE>   11
 
                    The Information Agent for the Offer is:
 
                               MORROW & CO., INC.
                           445 Park Avenue, 5th Floor
                            New York, New York 10022
                     Banks and Brokerage Firms Please Call:
                                 (800) 662-5200
 
                           Stockholders Please Call:
                                 (800) 566-9061
 
                                       11

<PAGE>   1
 
                       NOTICE OF GUARANTEED DELIVERY FOR
                        TENDER OF SHARES OF COMMON STOCK
 
                                       OF
 
                           AMERICAN BUILDINGS COMPANY
 
                                       TO
 
                             ABCO ACQUISITION CORP.
 
                     AN INDIRECT WHOLLY-OWNED SUBSIDIARY OF
                            [ONEX CORPORATION LOGO]
 
                   (NOT TO BE USED FOR SIGNATURE GUARANTEES)
 
     This Notice of Guaranteed Delivery, or one substantially in the form
hereof, must be used to accept the Offer (as defined below) if certificates
evidencing shares of Common Stock, par value $.01 per share (the "Shares"), of
American Buildings Company, a Delaware corporation (the "Company"), are not
immediately available, or if the procedure for book-entry transfer cannot be
completed on a timely basis or time will not permit all required documents to
reach the Depositary on or prior to the Expiration Date (as defined in the Offer
to Purchase, dated April 13, 1999 (the "Offer to Purchase")). Such form may be
delivered by hand, facsimile transmission or mail to the Depositary. See Section
3 of the Offer to Purchase.
 
                        The Depositary for the Offer is:
 
                            AMERICAN STOCK TRANSFER
                                & TRUST COMPANY
 
                             Facsimile Copy Number:
 
                                 (718) 234-5001
 
                             Confirm by Telephone:
 
                                 (718) 921-8200
 
                             For Information Call:
 
                                 (718) 921-8200
 
     By First Class Mail, By Express Mail or Overnight Courier, or By Hand
 
                            American Stock Transfer
                                & Trust Company
 
                                 40 Wall Street
                                   46th Floor
                               New York, NY 10005
 
     DELIVERY OF THIS NOTICE OF GUARANTEED DELIVERY TO AN ADDRESS OTHER THAN AS
SET FORTH ABOVE OR TRANSMISSION OF INSTRUCTIONS VIA FACSIMILE TRANSMISSION OTHER
THAN AS SET FORTH ABOVE WILL NOT CONSTITUTE A VALID DELIVERY.
<PAGE>   2
 
Ladies and Gentlemen:
 
     The undersigned hereby tenders to ABCO Acquisition Corp., a Delaware
corporation, upon the terms and subject to the conditions set forth in the Offer
to Purchase and the related Letter of Transmittal (which together, as the same
may be amended as supplemented from time to time, constitute the "Offer"),
receipt of which is hereby acknowledged, the number of Shares specified below
pursuant to the guaranteed delivery procedures described in Section 3 of the
Offer to Purchase.
 
Number of Shares:
- -------------------------------------
 
Certificate Nos. (If Available):
 
- ----------------------------------------------------------
 
- ----------------------------------------------------------
 
[ ] Check box if Shares will be delivered by book-entry transfer:
 
Account Number:
- --------------------------------------
 
Dated:
- --------------------------------------------, 1999
SIGN HERE
Name(s) of Holders(s):
 
- -----------------------------------------------------------
 
- -----------------------------------------------------------
 
                                (Signature(s))
 
- -----------------------------------------------------------
 
- -----------------------------------------------------------
                                (Print Name(s))
 
- -----------------------------------------------------------
 
- -----------------------------------------------------------
                              (Print Address(es))
 
- -----------------------------------------------------------
                      (Area Code and Telephone Number(s))
 
- -----------------------------------------------------------
            (Taxpayer Identification or Social Security Number(s))
 
                                   GUARANTEE
                    (NOT TO BE USED FOR SIGNATURE GUARANTEE)
 
      The undersigned, a member in good standing of the Security Transfer
 Agent's Medallion Program, the New York Stock Exchange Medallion Signature
 Program or the Stock Exchange Medallion Program (each, an "Eligible
 Institution"), (a) represents that the above named person(s) own(s) the Shares
 tendered hereby within the meaning of Rule 14e-4 promulgated under the
 Securities Exchange Act of 1934, as amended (the "Exchange Act"), (b)
 represents that such tender of Shares complies with Rule 14e-4 under the
 Exchange Act, and (c) guarantees delivery to the Depositary, at one of its
 addresses set forth above, of certificates representing the Shares tendered
 hereby in proper form for transfer, or confirmation of book-entry transfer of
 such Shares into the Depositary's account at The Depository Trust Company, in
 each case with delivery of a properly completed and duly executed Letter of
 Transmittal (or facsimile thereof) with any required signature guarantees, or
 an Agent's Message in the case of a book-entry transfer, and any other
 required documents, within three Nasdaq National Market trading days after the
 date hereof.
 
- ----------------------------------------------------------
 
                                 (Name of Firm)
 
- ----------------------------------------------------------
                             (Authorized Signature)
 
- ----------------------------------------------------------
                                   (Address)
 
- ----------------------------------------------------------
                                   (Address)
 
- -----------------------------------------------------------
                                    (Title)
 
Name:
- ---------------------------------------------------
                            (Please Type or Print)
 
- -----------------------------------------------------------
                         (Area Code and Telephone No.)
 
Dated:
- --------------------------------------------, 1999
 
NOTE:  DO NOT SEND STOCK CERTIFICATES WITH THIS NOTICE. STOCK CERTIFICATES
SHOULD BE SENT WITH YOUR LETTER OF TRANSMITTAL.
                                        2

<PAGE>   1
 
                           OFFER TO PURCHASE FOR CASH
                     ALL OUTSTANDING SHARES OF COMMON STOCK
 
                                       OF
 
                           AMERICAN BUILDINGS COMPANY
 
                                       AT
 
                               $36 NET PER SHARE
 
                                       BY
 
                             ABCO ACQUISITION CORP.
 
                     AN INDIRECT WHOLLY-OWNED SUBSIDIARY OF
                            [ONEX CORPORATION LOGO]
 
       THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW
     YORK CITY TIME, ON MONDAY, MAY 10, 1999, UNLESS THE OFFER IS EXTENDED.
 
                                                                  April 13, 1999
To Broker, Dealers, Commercial Banks,
Trust Companies And Other Nominees:
 
     We have been appointed by ABCO Acquisition Corp., a Delaware corporation
("Purchaser"), a wholly-owned subsidiary of ABCO Holdings Corp., a Delaware
corporation ("Parent") and an indirect wholly-owned subsidiary of Onex
Corporation, an Ontario corporation, to act as Information Agent in connection
with the Purchaser's offer to purchase all of the outstanding shares of common
stock, par value $.01 per share (the "Shares"), of American Buildings Company, a
Delaware corporation (the "Company"), at a price of $36 per Share (the "Offer
Price"), net to the seller in cash, upon the terms and subject to the conditions
set forth in the Offer to Purchase, dated April 13, 1999 (the "Offer to
Purchase"), and the related Letter of Transmittal (which together constitute the
"Offer"), copies of which are enclosed herewith. The Offer is being made in
connection with the Agreement and Plan of Merger, dated as of April 7, 1999,
among Parent, Purchaser and the Company (the "Merger Agreement").
 
     Please furnish copies of the enclosed materials to those of your clients
for whose accounts you hold Shares registered in your name or in the name of
your nominee.
 
     THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS, THERE BEING VALIDLY
TENDERED AND NOT WITHDRAWN PRIOR TO THE EXPIRATION OF THE OFFER THAT NUMBER OF
SHARES WHICH, TOGETHER WITH THE SHARES THEN OWNED BY PURCHASER AND ITS
AFFILIATES, WOULD CONSTITUTE A MAJORITY OF THE OUTSTANDING SHARES ON A
FULLY-DILUTED BASIS (AS DEFINED IN THE OFFER TO PURCHASE).
<PAGE>   2
 
     For your information and for forwarding to your clients, we are enclosing
the following documents:
 
          1.  The Offer to Purchase.
 
          2.  The Letter of Transmittal to be used by stockholders of the
     Company in accepting the Offer. Facsimile copies of the Letter of
     Transmittal (with manual signatures) may be used to tender Shares.
 
          3.  A letter to stockholders of the Company from William L. Selden and
     Robert T. Ammerman, Chairman of the Board of Directors and Chief Executive
     Officer of the Company, respectively, together with a Solicitation/
     Recommendation Statement on Schedule 14D-9 filed by the Company with the
     Securities and Exchange Commission and mailed to the stockholders of the
     Company.
 
          4.  A printed form of letter which may be sent to your clients for
     whose account you hold Shares in your name or in the name of your nominee
     with space provided for obtaining such clients' instructions with regard to
     the Offer.
 
          5.  The Notice of Guaranteed Delivery to be used to accept the Offer
     if certificates representing Shares are not immediately available or if
     time will not permit all required documents to reach the Depositary prior
     to the Expiration Date (as defined in Section 1 of the Offer to Purchase)
     or if the procedures for book-entry transfer cannot be completed on a
     timely basis.
 
          6.  Guidelines of the Internal Revenue Service for Certification of
     Taxpayer Identification Number on Substitute Form W-9.
 
          7.  A return envelope addressed to American Stock Transfer & Trust
     Company, as Depositary.
 
     Your attention is directed to the following:
 
          1.  The Offer Price is $36 per Share, net to the seller in cash.
 
          2.  THE BOARD OF DIRECTORS OF THE COMPANY HAS UNANIMOUSLY (WITH ONE
     DIRECTOR NOT PRESENT) APPROVED THE MERGER AGREEMENT, THE OFFER AND THE
     MERGER (AS DEFINED IN THE OFFER TO PURCHASE) AND DEEMED THEM TO BE
     ADVISABLE, HAS DETERMINED THAT THE TERMS OF THE OFFER AND THE MERGER ARE
     FAIR TO, AND IN THE BEST INTERESTS OF, THE STOCKHOLDERS OF THE COMPANY AND
     RECOMMENDS THAT THE STOCKHOLDERS OF THE COMPANY ACCEPT THE OFFER AND TENDER
     THEIR SHARES PURSUANT TO THE OFFER.
 
          3.  The Offer and withdrawal rights will expire at 12:00 Midnight, New
     York City time, on Monday, May 10, 1999, unless the Offer is extended.
 
          4.  The Offer is being made for all of the outstanding Shares. The
     Offer is conditioned upon, among other things, there being validly tendered
     and not withdrawn prior to the expiration of the Offer that number of
     Shares which, together with the Shares then owned by Purchaser and its
     affiliates, would constitute a majority of the outstanding Shares on a
     fully-diluted basis (as described in the Offer to Purchase) on the date of
     purchase.
 
          5.  Stockholders who tender Shares will not be obligated to pay
     brokerage fees, commissions or, except as set forth in Instruction 6 of the
     Letter of Transmittal, transfer taxes on the purchase of Shares by
     Purchaser pursuant to the Offer.
 
     Upon the terms and subject to the conditions of the Offer (including, if
the Offer is extended or amended, the terms and conditions of any such extension
or amendment), Purchaser will accept for payment and pay for all Shares which
are validly tendered on or prior to the Expiration Date and not theretofore
withdrawn pursuant to the Offer. In all cases, payment for Shares accepted for
payment pursuant to the Offer will be made only after timely receipt by the
Depositary of (i) certificates representing such Shares (or a timely
confirmation of a book-entry transfer of such Shares into the Depositary's
account at The Depository Trust Company, pursuant to the procedures described in
Section 3 of the Offer to Purchase), (ii) a properly completed and duly executed
Letter of Transmittal (or facsimile thereof) with any required signature
guarantees (or, in connection with a book-entry transfer, an Agent's Message (as
defined in Section 3 of the Offer to Purchase)), and (iii) all other documents
required by the Letter of Transmittal.
 
     If holders of Shares wish to tender, but it is impracticable for them to
forward their certificates or other required documents prior to the expiration
of the Offer, a tender may be effected by following the guaranteed delivery
procedures specified under Section 3, "Procedure for Tendering Shares," in the
Offer to Purchase.
 
                                        2
<PAGE>   3
 
     Purchaser will not pay any fees or commissions to any broker or dealer or
to any other person (other than the Information Agent) in connection with the
solicitation of tenders of Shares pursuant to the Offer. Purchaser will,
however, upon request, reimburse you for customary mailing and handling expenses
incurred by you in forwarding the enclosed materials to your clients. Purchaser
will pay or cause to be paid any transfer taxes payable on the transfer of
Shares to it, except as otherwise provided in Instruction 6 of the enclosed
Letter of Transmittal.
 
     YOUR PROMPT ACTION IS REQUESTED. WE URGE YOU TO CONTACT YOUR CLIENTS AS
PROMPTLY AS POSSIBLE. PLEASE NOTE THAT THE OFFER AND WITHDRAWAL RIGHTS WILL
EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME, ON MONDAY, MAY 10, 1999, UNLESS
THE OFFER IS EXTENDED.
 
     Any inquiries you may have with respect to the Offer should be directed to,
and additional copies of the enclosed materials may be obtained by contacting,
the undersigned at (800) 566-9061. Banks and brokerage firms please call (800)
662-5200.
 
                                         Very truly yours,
 
                                         MORROW & CO., INC.
 
NOTHING CONTAINED HEREIN OR IN THE ENCLOSED DOCUMENTS SHALL CONSTITUTE YOU OR
ANY PERSON AS AN AGENT OF PURCHASER, PARENT, ONEX CORPORATION, THE DEPOSITARY OR
THE INFORMATION AGENT, OR ANY AFFILIATE OF ANY OF THE FOREGOING, OR AUTHORIZE
YOU OR ANY OTHER PERSON TO GIVE ANY INFORMATION OR USE ANY DOCUMENT OR MAKE ANY
STATEMENTS ON BEHALF OF ANY OF THEM IN CONNECTION WITH THE OFFER OTHER THAN THE
DOCUMENTS ENCLOSED AND THE STATEMENTS CONTAINED THEREIN.
 
                                        3

<PAGE>   1
 
                           OFFER TO PURCHASE FOR CASH
                     ALL OUTSTANDING SHARES OF COMMON STOCK
 
                                       OF
 
                           AMERICAN BUILDINGS COMPANY
                                       AT
 
                               $36 NET PER SHARE
 
                                       BY
 
                             ABCO ACQUISITION CORP.
                     AN INDIRECT WHOLLY-OWNED SUBSIDIARY OF
                            [ONEX CORPORATION LOGO]
 
       THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW
     YORK CITY TIME, ON MONDAY, MAY 10, 1999, UNLESS THE OFFER IS EXTENDED.
 
                                                                  April 13, 1999
 
To Our Clients:
 
     Enclosed for your consideration is an Offer to Purchase, dated April 13,
1999 (the "Offer to Purchase"), and the related Letter of Transmittal (which
together constitute the "Offer") relating to the offer by ABCO Acquisition
Corp., a Delaware corporation ("Purchaser"), a wholly-owned subsidiary of ABCO
Holdings Corp., a Delaware corporation ("Parent") and an indirect wholly-owned
subsidiary of Onex Corporation, an Ontario corporation, to purchase all of the
outstanding shares of common stock, par value $.01 per share (the "Shares"), of
American Buildings Company, a Delaware corporation (the "Company"), at a price
of $36 per Share (the "Offer Price"), net to the seller in cash, upon the terms
and subject to the conditions set forth in the Offer. The Offer is being made in
connection with the Agreement and Plan of Merger, dated as of April 7, 1999,
among Parent, Purchaser and the Company (the "Merger Agreement").
 
     WE ARE THE HOLDER OF RECORD OF SHARES FOR YOUR ACCOUNT. A TENDER OF SUCH
SHARES CAN BE MADE ONLY BY US AS THE HOLDER OF RECORD AND PURSUANT TO YOUR
INSTRUCTIONS. THE LETTER OF TRANSMITTAL IS FURNISHED TO YOU FOR YOUR INFORMATION
ONLY AND CANNOT BE USED BY YOU TO TENDER SHARES HELD BY US FOR YOUR ACCOUNT.
 
     We request instructions as to whether you wish to have us tender on your
behalf any or all of the Shares held by us for your account, pursuant to the
terms and conditions set forth in the Offer.
 
     Your attention is directed to the following:
 
          1.  The Offer Price is $36 per Share, net to you in cash.
 
          2.  THE BOARD OF DIRECTORS OF THE COMPANY HAS UNANIMOUSLY (WITH ONE
     DIRECTOR NOT PRESENT) APPROVED THE MERGER AGREEMENT, THE OFFER AND THE
     MERGER (AS DEFINED IN THE OFFER TO PURCHASE) AND DEEMED THEM TO BE
     ADVISABLE, HAS DETERMINED UNANIMOUSLY (WITH ONE DIRECTOR NOT PRESENT) THAT
     THE TERMS OF THE OFFER AND THE MERGER ARE FAIR TO, AND IN THE BEST
     INTERESTS OF, STOCKHOLDERS OF THE COMPANY, AND RECOMMENDS THAT THE
     STOCKHOLDERS OF THE COMPANY ACCEPT THE OFFER AND TENDER THEIR SHARES
     PURSUANT TO THE OFFER.
 
          3.  The Offer and withdrawal rights will expire at 12:00 Midnight, New
     York City time, on Monday, May 10, 1999, unless the Offer is extended.
 
          4.  The Offer is being made for all of the outstanding Shares. The
     Offer is conditioned upon, among other things, there being validly tendered
     and not withdrawn prior to the expiration of the Offer that number of
     Shares which, together with the Shares then owned by Purchaser and its
     affiliates, would constitute a majority of the outstanding Shares on a
     fully-diluted basis (as described in the Offer to Purchase) on the date of
     purchase.
<PAGE>   2
 
          5.  Stockholders who tender Shares will not be obligated to pay
     brokerage fees, commissions or, except as set forth in Instruction 6 of the
     Letter of Transmittal, transfer taxes on the purchase of Shares by
     Purchaser pursuant to the Offer.
 
     If you wish to have us tender any or all of your Shares, please complete,
sign and return the instruction form set forth below. An envelope to return your
instructions to us is enclosed. If you authorize the tender of your Shares, all
such Shares will be tendered unless otherwise specified on the instruction form
set forth below. PLEASE FORWARD YOUR INSTRUCTIONS TO US AS SOON AS POSSIBLE TO
ALLOW US AMPLE TIME TO TENDER YOUR SHARES ON YOUR BEHALF PRIOR TO THE EXPIRATION
OF THE OFFER.
 
     The Offer is made solely by the Offer to Purchase and the related Letter of
Transmittal and any supplements and amendments thereto. Purchaser is not aware
of any state where the making of the Offer is prohibited by administrative or
judicial action pursuant to any valid state statute. If Purchaser becomes aware
of any valid state statute prohibiting the making of the Offer or the acceptance
of Shares pursuant thereto, Purchaser will make a good faith effort to comply
with any such state statute or seek to have such statute declared inapplicable
to the Offer. If, after such good faith effort, Purchaser cannot comply with any
such state statute, the Offer will not be made to (nor will tenders be accepted
from or on behalf of) the holders of Shares in such state. In any jurisdiction
where the securities, blue sky or other laws require the Offer to be made by a
licensed broker or dealer, the Offer will be deemed to be made on behalf of
Purchaser by one or more registered brokers or dealers licensed under the laws
of such jurisdiction.
<PAGE>   3
 
               INSTRUCTIONS WITH RESPECT TO THE OFFER TO PURCHASE
                FOR CASH ALL OUTSTANDING SHARES OF COMMON STOCK
                                       OF
                           AMERICAN BUILDINGS COMPANY
 
     The undersigned acknowledge(s) receipt of your letter and the enclosed
Offer to Purchase, dated April 13, 1999, and the related Letter of Transmittal
(which together constitute the "Offer") relating to the offer by ABCO
Acquisition Corp., a Delaware corporation ("Purchaser"), to purchase all of the
outstanding shares of common stock, par value $.01 per share (the "Shares"), of
American Buildings Company, a Delaware corporation, at a price of $36 per Share,
net to the seller in cash.
 
     This will instruct you to tender to Purchaser the number of Shares
indicated below (or if no number is indicated below, all Shares) held by you for
the account of the undersigned, upon the terms and subject to the conditions set
forth in the Offer.
 
<TABLE>
<S>                                                               <C>
 
Number of Shares to be Tendered:*                                                          SIGN HERE
                    Shares
- -------------------
                                                                  -----------------------------------------------------------
                           

                                                                  -----------------------------------------------------------
                                                                                         SIGNATURE(S)
 
Account Number: -------------------------------                   -----------------------------------------------------------


                                                                  -----------------------------------------------------------
                                                                           PLEASE PRINT NAME(S) AND ADDRESS(ES) HERE
 

                                                                  -----------------------------------------------------------
Dated:            , 1999                                                       AREA CODE AND TELEPHONE NUMBER(S)


                                                                  -----------------------------------------------------------
                                                                         TAX IDENTIFICATION OR SOCIAL SECURITY NUMBER
</TABLE>
 
- ---------------
 
* Unless otherwise indicated, it will be assumed that all of your Shares held by
  us for your account are to be tendered in the Offer.

<PAGE>   1
 
            GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
                         NUMBER ON SUBSTITUTE FORM W-9
 
GUIDELINES FOR DETERMINING THE PROPER IDENTIFICATION NUMBER TO GIVE THE
PAYOR.--Social Security numbers have nine digits separated by two hyphens: i.e.
000-00-0000. Employer identification numbers have nine digits separated by only
one hyphen: i.e. 00-0000000. The table below will help determine the number to
give the payor.
 
<TABLE>
<C>  <S>                                 <C>
- ------------------------------------------------------------
                                         GIVE THE TAXPAYER
              FOR THIS TYPE OF ACCOUNT:  IDENTIFICATION
                                         NUMBER OF--
- ------------------------------------------------------------
 
 1.  An individual's account             The individual
 2.  Two or more individuals (joint      The actual owner of
     account)                            the account or, if
                                         combined funds, any
                                         one of the
                                         individuals(1)
 3.  Husband and wife (joint account)    The actual owner of
                                         the account or, if
                                         joint funds, either
                                         person (1)
 4.  Custodian account of a minor        The minor(2)
     (Uniform Gift to Minors Act)
 5.  Adult and minor (joint account)     The adult or, if
                                         the minor is the
                                         only contributor,
                                         the minor(1)
 6.  Account in the name of guardian or  The ward, minor, or
     committee for a designated ward,    incompetent
     minor, or incompetent person        person(3)
 7.  a. The usual revocable savings      The grantor-
        trust account (grantor is also   trustee(1)
        trustee)
     b. So-called trust account that is  The actual owner(1)
        not a legal or valid trust
        under State law
 8.  Sole proprietorship account         The Owner(4)
- ------------------------------------------------------------
- ------------------------------------------------------------
                                         GIVE THE TAXPAYER
              FOR THIS TYPE OF ACCOUNT:  IDENTIFICATION
                                         NUMBER OF--
- ------------------------------------------------------------
 
 9.  A valid trust, estate or pension    The Legal entity
     trust                               (Do not furnish the
                                         identifying number
                                         of the personal
                                         representative or
                                         trustee unless the
                                         legal entity itself
                                         is not designated
                                         in the account
                                         title.)(5)
10.  Corporate account                   The corporation
11.  Religious, charitable, or           The organization
     educational organization account
12.  Partnership account held in the     The partnership
     name of the business
13.  Association, club, or other tax-    The organization
     exempt organization
14.  A broker or registered nominee      The broker or
                                         nominee
15.  Account with the Department of      The public entity
     Agriculture in the name of a
     public entity (such as a State or
     local government, school district,
     or prison) that receives
     agricultural program payments
- ------------------------------------------------------------
</TABLE>
 
(1) List first and circle the name of the person whose number you furnish.
(2) Circle the minor's name and furnish the minor's social security number.
(3) Circle the ward's, minor's or incompetent person's name and furnish such
    person's social security number.
(4) Show the name of the owner.
(5) List first and circle the name of the legal trust, estate, or pension trust.
 
NOTE: If no name is circled when there is more than one name, the number will be
      considered to be that of the first name listed.
<PAGE>   2
 
OBTAINING A NUMBER
If you do not have a taxpayer identification number or you do not know your
number, obtain Form SS-5, Application for a Social Security Number Card, or Form
SS-4, Application for Employer Identification Number, at the local office of the
Social Security Administration or the Internal Revenue Service and apply for a
number.
 
PAYEES EXEMPT FROM BACKUP WITHHOLDING
Payees specifically exempted from backup withholding on ALL payments include the
following:
  - A corporation.
  - A financial institution.
  - An organization exempt from tax under section 501(a), or an individual
    retirement plan.
  - The United States or any agency or instrumentality thereof.
  - A State, the District of Columbia, a possession of the United States or any
    subdivision or instrumentality thereof.
  - A foreign government, a political subdivision of a foreign government, or
    any agency or instrumentality thereof.
  - An international organization or any agency, or instrumentality thereof.
  - A registered dealer in securities or commodities registered in the U.S. or a
    possession of the U.S.
  - A real estate investment trust.
  - A common trust fund operated by a bank under section 584(a).
  - An exempt charitable remainder trust, or a non-exempt trust described in
    section 4947(a)(1).
  - An entity registered at all times under the Investment Company Act of 1940.
  - A foreign central bank of issue.
  Payments of dividends and patronage dividends not generally subject to backup
withholding include the following:
  - Payments to nonresident aliens subject to withholding under section 1441.
  - Payments to partnerships not engaged in a trade or business in the U.S. and
    which have at least one nonresident partner.
  - Payments of patronage dividends where the amount received is not paid in
    money.
  - Payments made by certain foreign organizations.
  - Payments made to a nominee.
  Payments of interest generally subject to backup withholding include the
following:
  - Payments of interest on obligations issued by individuals. Note: You may be
    subject to backup withholding if this interest is $600 or more and is paid
    in the course of the payor's trade or business and you have not provided
    your correct taxpayer identification number to the payor.
  - Payments of tax-exempt interest (including exempt-interest dividends under
    section 852).
  - Payments described in section 6049(b)(5) to nonresident aliens.
  - Payments on tax-free covenant bonds under section 1451.
  - Payments made by certain foreign organizations.
  - Payments made to a nominee.
Exempt payees described above should file Form W-9 to avoid possible erroneous
backup withholding. FILE THIS FORM WITH THE PAYOR.  FURNISH YOUR TAXPAYER
IDENTIFICATION NUMBER, WRITE "EXEMPT" ON THE FACE OF THE FORM, AND RETURN IT TO
THE PAYOR. IF THE PAYMENTS ARE INTEREST, DIVIDENDS, OR PATRONAGE DIVIDENDS, ALSO
SIGN AND DATE THE FORM.
 
  Certain payments other than interest, dividends, and patronage dividends, that
are not subject to information reporting are also not subject to backup
withholding. For details, see the regulations under sections 6041, 6041A(a),
6045, and 6050A.
 
PRIVACY ACT NOTICE.--Section 6109 requires most recipients of dividend,
interest, or other payments to give taxpayer identification numbers to payors
who must report the payments to the IRS. The IRS uses the numbers for
identification purposes. Payors must be given the numbers whether or not
recipients are required to file a tax return. Payors must generally withhold 31%
of taxable interest, dividend, and certain other payments to a payee who does
not furnish a taxpayer identification number to a payor. Certain penalties may
also apply.
 
PENALTIES
(1) PENALTY FOR FAILURE TO FURNISH TAXPAYER IDENTIFICATION NUMBER.--If you fail
to furnish your taxpayer identification number to a payor, you are subject to a
penalty of $50 for each such failure unless your failure is due to reasonable
cause and not to willful neglect.
(2) FAILURE TO REPORT CERTAIN DIVIDEND AND INTEREST PAYMENTS.--If you fail to
include any portion of an includible payment for interest, dividends, or
patronage dividends in gross income, such failure will generally be treated as
being due to negligence and will be subject to a penalty of 20% on any portion
of an underpayment attributable to that failure.
(3) CIVIL PENALTY FOR FALSE INFORMATION WITH RESPECT TO WITHHOLDING.--If you
make a false statement with no reasonable basis which results in no imposition
of backup withholding, you are subject to a penalty of $500.
(4) CRIMINAL PENALTY FOR FALSIFYING INFORMATION.--Falsifying certifications or
affirmations may subject you to criminal penalties including fines and/or
imprisonment.
 
FOR ADDITIONAL INFORMATION CONTACT YOUR TAX CONSULTANT OR THE INTERNAL REVENUE
SERVICE

<PAGE>   1
 
[NOTE: AMOUNTS IN CANADIAN DOLLARS UNLESS OTHERWISE INDICATED.]
 
                            [ONEX CORPORATION LOGO]
 
STOCK SYMBOL: TSE, ME: OCX
TORONTO, ONTARIO -- APRIL 8, 1999
 
               ONEX ACQUIRES LEADING METAL BUILDING MANUFACTURER
- --------------------------------------------------------------------------------
 
TORONTO, ONTARIO -- Onex Corporation announced today that two of its
subsidiaries have entered into a definitive merger agreement to acquire all the
outstanding common shares of American Buildings Company (NASDAQ: ABCO) at a
price of US$36.00 per share in cash. The total value of the transaction is
approximately $405 million.
 
American Buildings Company, headquartered in Eufaula, Alabama, is a diversified
manufacturer and marketer of metal building products throughout North America.
Principal products include metal buildings, roofing and upward-acting door
systems. The company reported 1998 sales from continuing operations of $660
million.
 
The Onex subsidiaries will commence a tender offer for all the outstanding
shares of American Buildings Company within five business days. The Board of
Directors of the company has approved the merger agreement and has recommended
that shareholders tender their shares to the offer. The Board of Directors of
American Buildings Company has received a fairness opinion from Warburg Dillon
Read LLC.
 
The offer is subject to customary conditions, including there having been
validly tendered by the expiration date and not withdrawn shares that, together
with shares held by Onex and its subsidiaries, constitute a majority of American
Buildings Company's outstanding shares, on a fully-diluted basis.
 
The offer will be made only upon and subject to the terms and conditions of the
Offer to Purchase and the related Letter of Transmittal.
 
"American Buildings is an outstanding company with an excellent management team
and is a leader in its industry," said Mark L. Hilson, Vice-President of Onex
Corporation. "We believe that the price we are paying, which is 65% above the
closing price for the shares on April 7 on NASDAQ, shows the high regard we have
for the business."
 
Onex will be the majority and controlling shareholder of the company and will
invest approximately $145 million in the equity. It is anticipated that the
management of American Buildings Company will become significant investors as
well.
 
Onex Corporation is a diversified company with annual consolidated revenues of
$8.8 billion, consolidated assets of $6.8 billion and 53,000 employees. Onex was
ranked the 9th-largest company in Canada in The Financial Post 500. It operates
through autonomous subsidiaries that are leaders in their industries. They
include Sky Chefs, Celestica Inc., ClientLogic, Lantic Sugar Limited, Dura
Automotive Systems, Inc., Tower Automotive, Inc., Phoenix Pictures Inc. and
Vencap, Inc. Onex shares trade on the Toronto and Montreal exchanges under the
stock symbol OCX.
 
FOR FURTHER INFORMATION: MARK L. HILSON OR NIGEL S. WRIGHT -- (416) 362-7711
 
- --------------------------------------------------------------------------------

<PAGE>   1
 
                            [ONEX CORPORATION LOGO]
 
                                 April 7, 1999
 
American Buildings Company
1150 State Docks Road
P.O. Box 800
Eufaula, AL 36027
 
Attention:  Mr. William Selden, Chairman
 
Gentlemen:
 
     We refer to the Agreement and Plan of Merger (the "Merger Agreement") dated
as of the date hereof among ABCO Acquisition Corp., ABCO Holdings Corp. and
American Buildings Company (the "Company"). Capitalized terms used but not
defined herein have the meanings set forth in the Merger Agreement.
 
     In consideration for and in order to induce the Company to enter into and
perform its obligations under the Merger Agreement, including, without
limitation, its obligations under Section 9.03(b) thereof, we agree to provide
or cause to be provided to Parent or Purchaser on a timely basis (a) the funds
necessary to (i) purchase all outstanding shares of Company Common Stock (on a
fully diluted basis) pursuant to the Offer and the Merger, and (ii) pay all fees
and expenses related to the transactions contemplated by the Merger Agreement,
and (b) in the event of termination of the Merger Agreement by the Company as
provided in Section 9.01 of the Merger Agreement, the funds necessary to pay the
liabilities or obligations, if any, of Parent or Purchaser pursuant to Section
9.02 of the Merger Agreement.
 
                                          Very truly yours,
 
                                          ONEX CORPORATION
 
                                          By: /s/ MARK L. HILSON
 
                                            ------------------------------------
                                            Name:  Mark L. Hilson
                                            Title:  Vice President
 
ACKNOWLEDGED AND AGREED:
 
AMERICAN BUILDINGS COMPANY
 
By: /s/ WILLIAM L. SELDEN
 
    --------------------------------------------------------
    Name:  William L. Selden
    Title:  Chairman
 
                                        5

<PAGE>   1
 
                           AMERICAN BUILDINGS COMPANY
                             1150 State Docks Road
                             Eufaula, Alabama 36027
                                 (205) 687-2032
 
March 8, 1999
 
Onex Corporation
161 Bay Street
Toronto, Canada M5J 2S1
Attn: Mr. Mark L. Hilson
 
Gentlemen:
 
     In connection with your consideration of a possible negotiated transaction
with American Buildings Company (together with its subsidiaries, the "Company"),
the Company is prepared to make available to you certain information concerning
the business, financial condition, operations, assets and liabilities of the
Company, including information which is not available to the general public. As
a condition to such information being furnished to you and your directors,
officers, employees, agents and advisors (including, without limitation,
attorneys, accountants, consultants, bankers and financial advisors)
(collectively, "Representatives"), you agree to treat any information concerning
the Company (whether prepared by the Company, its advisors or otherwise and
irrespective of the form of communication) which is furnished to you or to your
Representatives now or in the future by or on behalf of the Company (herein
collectively referred to as the "Evaluation Material") in accordance with the
provisions of this letter agreement, and to take or abstain from taking certain
other actions hereinafter set forth.
 
     The term "Evaluation Material" also shall be deemed to include all notes,
analyses, compilations, studies, interpretations or other documents prepared by
you or your Representatives which contain, reflect or are based upon, in whole
or in part, the information furnished to you or your Representatives pursuant
hereto. The term "Evaluation Material" does not include information which (i) is
or becomes generally available to the public other than as a result of a
disclosure by you or your Representatives, (ii) was within your possession prior
to its being furnished to you by or on behalf of the Company pursuant hereto,
provided that the source of such information was not known by you to be bound by
a confidentiality agreement with or other contractual, legal or fiduciary
obligation of confidentiality to the Company or any other party with respect to
such information or (iii) becomes available to you on a non-confidential basis
from a source other than the Company or any of its Representatives, provided
that such source is not bound by a confidentiality agreement with or other
contractual, legal or fiduciary obligation of confidentiality to the Company or
any other party with respect to such information.
 
     You hereby agree that you and your Representatives shall use the Evaluation
Material solely for the purpose of evaluating a possible negotiated transaction
between the Company and you, that the Evaluation Material will be kept
confidential and that you and your Representatives will not disclose any of the
Evaluation Material in any manner whatsoever; provided, however, that (i) you
may make any disclosure of such information to which the Company gives its prior
written consent and (ii) any of such information may be disclosed to your
Representatives who need to know such information for the sole purpose of
evaluating a possible negotiated transaction with the Company, who agree to keep
such information confidential and who are provided with a copy of this letter
agreement and agree to be bound by the terms hereof to the same extent as if
they were parties hereto. In any event, you shall be responsible for any breach
of this letter agreement by any of your Representatives and you agree, at your
sole expense, to take all reasonable measures (including but not limited to
court proceedings) to restrain your Representatives from prohibited or
unauthorized disclosure or use of the Evaluation Material.
 
     In addition, you agree that, without the prior written consent of the
Company, you and your Representatives will not disclose to any other person the
fact that the Evaluation Material has been made available to you, that
discussions or negotiations are taking place concerning a possible transaction
involving
<PAGE>   2
 
the Company or any of the terms, conditions or other facts with respect thereto
(including the status thereof), provided that you may make such disclosure if
you have received the written opinion of your outside counsel that such
disclosure must be made by you in order that you not commit a violation of law.
Without limiting the generality of the foregoing, you further agree that,
without the prior written consent of the Company, you will not, directly or
indirectly, enter into any agreement, arrangement or understanding, or any
discussions which might lead to such agreement, arrangement or understanding,
with any person regarding a possible transaction involving the Company. The term
"person" as used in this letter agreement shall be broadly interpreted to
include the media and any corporation, partnership, group, individual or other
entity.
 
     In the event that you or any of your Representatives are requested or
required (by oral questions, interrogatories, requests for information or
documents in legal proceedings, subpoena, civil investigative demand or other
similar process) to disclose any of the Evaluation Material, you shall provide
the Company with prompt written notice of any such request or requirement so
that the Company may seek a protective order or other appropriate remedy and/or
waive compliance with the provisions of this letter agreement. If, in the
absence of a protective order or other remedy or the receipt of a waiver by the
Company, you or any of your Representatives are nonetheless, in the written
opinion of counsel, legally compelled to disclose Evaluation Material to any
tribunal or else stand liable for contempt or suffer other censure or penalty,
you or your Representative may, without liability hereunder, disclose to such
tribunal only that portion of the Evaluation Material which such counsel advises
you is legally required to be disclosed, provided that you exercise your best
efforts to preserve the confidentiality of the Evaluation Material, including,
without limitation, by cooperating with the Company to obtain an appropriate
protective order or other reliable assurance that confidential treatment will be
accorded the Evaluation Material by such tribunal.
 
     If you decide that you do not wish to proceed with a transaction with the
Company, you will promptly inform the Company of that decision. If that case, or
at any time upon the written request of the Company for any reason, you will
promptly deliver to the Company all Evaluation Material (and all copies thereof)
furnished to you or your Representatives by or on behalf of the Company pursuant
hereto. In the event of such a decision or request, all other Evaluation
Material prepared by you or your Representatives shall be destroyed and no copy
thereof shall be retained. Notwithstanding the return or destruction of the
Evaluation Material, you and your Representatives will continue to be bound by
your obligations of confidentiality and other obligations hereunder.
 
     You understand and acknowledge that neither the Company nor any of its
Representatives or any of the Company's directors, officers, employees or
agents) make any representation or warranty, express or implied, as to the
accuracy or completeness of the Evaluation Material. You agree that neither the
Company nor any of its Representatives (including without limitation any of the
Company's directors, officers, employees or agents) shall have any liability to
you or to any of your Representatives relating to or resulting from the use of
the Evaluation Material or any errors therein or omissions therefrom. Only those
representations or warranties which are made in a final definitive agreement
regarding any transactions contemplated hereby, when, as and if executed, and
subject to such limitations and restrictions as may be specified therein, will
have any legal effect.
 
     You hereby acknowledge that you are aware, and that you will advise your
Representatives, that the United States securities laws prohibit any person who
has received from an issuer material, non-public information from purchasing or
selling securities of such issuer or from communicating such information to any
other person under circumstances in which it is reasonably foreseeable that such
person is likely to purchase or sell such securities.
 
     In consideration of the Evaluation Material being furnished to you, you
hereby agree that, for a period of two years from the date hereof, neither you
nor any of your affiliates will solicit to employ any of the current officers or
employees of the Company with whom you have had contact or who was specifically
identified to you during the period of your investigation of the Company, so
long as they are employed by the Company, without obtaining the prior written
consent of the Company. Provided, however, that hiring such person who has
responded to general advertisements not targeted at such person will not be
considered a violation of this paragraph.
 
                                        2
<PAGE>   3
 
     You further agree that, for a period of two years from the date of this
letter agreement, unless such shall have been specifically invited in writing by
the Company, neither you nor any of your affiliates (as such term is defined
under the Securities Exchange Act of 1934, as amended (the "Exchange Act")) or
Representatives will in any manner, directly or indirectly, (a) effect or seek,
offer or propose (whether publicly or otherwise) to effect, or cause or
participate in or in any way assist any other person to effect or seek, offer or
propose (whether publicly or otherwise) to effect or participate in, (i) any
acquisition of any securities (or beneficial ownership thereof) or assets of the
Company or any of its subsidiaries; (ii) any tender or exchange offer, merger or
other business combination involving the Company or any of its subsidiaries;
(iii) any recapitalization, restructuring, liquidation, dissolution or other
extraordinary transaction with respect to the Company or any of its
subsidiaries; or (iv) any "solicitation" of "proxies" (as such terms are used in
the proxy rules of the Securities and Exchange Commission) or consents to vote
any voting securities of the Company; (b) form, join or in any way participate
in a "group" (as defined under the Exchange Act); (c) otherwise act, alone or in
concert with others, to seek to control or influence the management, Board of
Directors or policies of the Company; (d) take any action which might force the
Company to make a public announcement regarding any of the types of matters set
forth in (a) above; or (e) enter into any discussions or arrangements with any
third party with respect to any of the foregoing. You also agree during such
period not to request the Company (or its directors, officers, employees or
agents), directly or indirectly, to amend or waive any provision of this
paragraph (including this sentence).
 
     You understand and agree that no contract or agreement providing for any
transaction involving the Company shall be deemed to exist between you and the
Company unless and until a final definitive agreement has been executed and
delivered, and you hereby waive, in advance, any claims (including, without
limitation, breach of contract) in connection with any transaction involving the
Company unless and until you and the Company shall have entered into a final
definitive agreement. You also agree that unless and until a final definitive
agreement regarding a transaction between the Company and you has been executed
and delivered, neither the Company nor you will be under any legal obligation of
any kind whatsoever with respect to such a transaction by virtue of this letter
agreement except for the matters specifically agreed to herein. You further
acknowledge and agree that the Company reserves the right, in its sole
discretion, to reject any and all proposals made by you or any of your
Representatives with regard to a transaction between the Company and you, and to
terminate discussions and negotiations with you at any time. You further
understand that (i) the Company and its Representatives shall be free to conduct
any process for any transaction involving the Company, if and as they in their
sole discretion shall determine (including, without limitation, negotiating with
any other interested parties and entering into a definitive agreement without
prior notice to you or any other person), (ii) any procedures relating to such
process or transaction may be changed at any time without notice to you or any
other person, and (iii) you shall not have any claims whatsoever against the
Company, its Representatives or any of their respective directors, officers,
stockholders, owners, affiliates or agents arising out of or relating to any
transaction involving the Company (other than those as against the parties to a
definitive agreement with you in accordance with the terms thereof) nor, unless
a definitive agreement is entered into with you, against any third party with
whom a transaction is entered into. Neither this paragraph nor any other
provision in this agreement can be waived or amended except by written consent
of the Company, which consent shall specifically refer to this paragraph (or
such provision) and explicitly make such waiver or amendment.
 
     It is understood and agreed that no failure or delay by the Company in
exercising any right, power or privilege hereunder shall operate as a waiver
thereof, nor shall any single or partial exercise thereof preclude any other or
future exercise thereof or the exercise of any other right, power or privilege
hereunder.
 
     It is further understood and agreed that money damages would not be
sufficient remedy for any breach of this letter agreement by you or any of your
Representatives and that the Company shall be entitled to equitable relief,
including injunction and specific performance, as a remedy for any such breach.
Such remedies shall not be deemed to be the exclusive remedies for a breach by
you of this letter agreement but shall be in addition to all other remedies
available at law or equity to the Company.
 
     This letter agreement is for the benefit of the Company, and its directors,
officers, stockholders, owners, affiliates and agents, and shall be governed by
and construed in accordance with the laws of the State of New
                                        3
<PAGE>   4
 
York. You also hereby irrevocably and unconditionally consent to submit to the
exclusive jurisdiction of the courts of the State of New York and of the United
States of America located in the State of New York for any actions, suits or
proceedings arising out of or relating to this agreement and the transactions
contemplated hereby (and you agree not to commence any action, suit or
proceeding relating thereto except in such courts), and further agree that
service of any process, summons, notice or document by U.S. registered mail to
your address set forth above shall be effective service of process for any
action, suit or proceeding brought against you in any such court. You hereby
irrevocably and unconditionally waive any objection to the laying of venue of
any action, suit or proceeding arising out of this agreement or the transactions
contemplated hereby, in the courts of the State of New York or the United States
of America located in the State of New York, and hereby further irrevocably and
unconditionally waive and agree not to plead or claim in any such court that any
such action, suit or proceeding brought in any such court has been brought in an
inconvenient forum.
 
     This agreement expires in 2 years from the date noted below.
 
     Please confirm your agreement with the foregoing by signing and returning
one copy of this letter to the undersigned, whereupon this letter agreement
shall become a binding agreement between you and the Company.
 
                                          Very truly yours,
 
                                          AMERICAN BUILDINGS COMPANY
 
                                          By: /s/ WILLIAM L. SELDEN
                                            ------------------------------------
                                            Name: William L. Selden
                                            Title:   Chairman of the Board
 
                                            Accepted and agreed as of
                                            the date first written above:
 
                                          ONEX CORPORATION
 
                                          By: /s/ MARK HILSON
                                            ------------------------------------
                                            Name: Mark Hilson
                                            Title:   Vice President
 
                                        4


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