<PAGE>
                                                                               .
                                                                               .
                                                                               .

                         NOTICE OF GUARANTEED DELIVERY

                                      FOR
                           TENDER OF ALL OUTSTANDING

<Table>
<S>                                                 <C>  <C>
              7 1/4% SENIOR NOTES DUE               AND            SENIOR FLOATING RATE NOTES DUE
                  OCTOBER 1, 2012                                          OCTOBER 1, 2010
                        OF                                                       OF
             AINSWORTH LUMBER CO. LTD.                                AINSWORTH LUMBER CO. LTD.
</Table>

     This Notice of Guaranteed Delivery relates to the offer by Ainsworth Lumber
Co. Ltd. ("Ainsworth") to exchange (a) US$1,000 in stated amount at maturity of
a new series of 7 1/4% Senior Notes due October 1, 2012 (the "New Fixed Rate
Notes") of Ainsworth for each US$1,000 in stated amount at maturity of
outstanding 7 1/4% Senior Notes due October 1, 2012 ("Original Fixed Rate
Notes") and (b) US$1,000 in stated amount at maturity of a new series of Senior
Floating Rate Notes due October 1, 2010 (the "New Floating Rate Notes", and,
together with the New Fixed Rate Notes, the "Exchange Notes") of Ainsworth for
each US$1,000 in stated amount at maturity of outstanding Senior Floating Rate
Notes due October 1, 2010 (the "Original Floating Rate Notes", and, together
with the Original Fixed Rate Notes, the "Original Notes") of Ainsworth.
Registered holders of outstanding Original Notes of Ainsworth who wish to tender
their Original Notes in exchange for a like principal amount of Exchange Notes
of Ainsworth upon the terms and subject to the conditions set forth in the
prospectus, dated           ,   (the "Prospectus") and the related letter of
transmittal (the "Letter of Transmittal") and, in each case, whose Original
Notes are not immediately available or who cannot deliver their Original Notes
and Letter of Transmittal (and any other documents required by the Letter of
Transmittal) to the Bank of New York (the "Exchange Agent") or cannot complete
the procedure for book-entry transfer prior to the Expiration Date, may use this
Notice of Guaranteed Delivery or one substantially equivalent hereto. This
Notice of Guaranteed Delivery may be delivered by hand or sent by facsimile
transmission (receipt confirmed by telephone and an original delivered by
guaranteed overnight delivery) or mail to the Exchange Agent. See "The Exchange
Offer -- Procedures for Tendering Original Notes" in the Prospectus. Capitalized
terms not defined herein have the meaning as defined in the Prospectus or the
Letter of Transmittal.

THE EXCHANGE OFFER WILL EXPIRE AT 5:00 P.M., NEW YORK CITY TIME, ON           ,
  (THE "EXPIRATION DATE") UNLESS THE OFFER IS EXTENDED BY AINSWORTH IN ITS SOLE
DISCRETION. TENDERS OF OUTSTANDING NOTES MAY BE WITHDRAWN AT ANY TIME PRIOR TO
5:00 P.M., NEW YORK CITY TIME, ON THE EXPIRATION DATE.

The Exchange Agent for the Exchange Offer is:

                              THE BANK OF NEW YORK

<Table>
<S>                                              <C>
      By Hand, Mail or Overnight Delivery                   By Facsimile Transmission
              The Bank of New York                      (for Eligible Institutions only):
           Corporate Trust Operations                             (212) 298-1915
            101 Barclay Street - 7E                         Attention: William Buckley
            New York, New York 01286
           Attention: William Buckley                         Confirm by Telephone:
                                                                  (212) 815-5788
             For Information Call:
                 (212) 815-5788
</Table>

                            ------------------------

     DELIVERY OF THIS NOTICE OF GUARANTEED DELIVERY TO AN ADDRESS OTHER THAN AS
SET FORTH ABOVE OR TRANSMISSION OF INSTRUCTIONS VIA A FACSIMILE TRANSMISSION TO
A NUMBER OTHER THAN AS SET FORTH ABOVE WILL NOT CONSTITUTE A VALID DELIVERY.

     THIS NOTICE OF GUARANTEED DELIVERY IS NOT TO BE USED TO GUARANTEE
SIGNATURES. IF A SIGNATURE ON A LETTER OF TRANSMITTAL IS REQUIRED TO BE
GUARANTEED BY AN ELIGIBLE INSTITUTION (AS DEFINED BY RULE 17AD-15 UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED (THE "EXCHANGE ACT")) , SUCH
SIGNATURE GUARANTEE MUST APPEAR IN THE APPLICABLE SPACE PROVIDED ON THE LETTER
OF TRANSMITTAL FOR GUARANTEE OF SIGNATURES.
<PAGE>

Ladies & Gentlemen:

     The undersigned hereby tender(s) to Ainsworth upon the terms and subject to
the conditions set forth in the Prospectus and the accompanying Letter of
Transmittal, receipt of which is hereby acknowledged, the aggregate principal
amount of Original Notes set forth below pursuant to the guaranteed delivery
procedures set forth in the Prospectus.

     The undersigned understands that tenders of Original Notes will be accepted
only in principal amounts equal to $1,000 or integral multiples thereof. The
undersigned understands that tenders of Original Notes pursuant to the Exchange
Offer may not be withdrawn after 5:00 p.m., New York City time on the business
day prior to the Expiration Date. Tenders of Original Notes may also be
withdrawn if the Exchange Offer is terminated without any such Original Notes
being purchased thereunder or as otherwise provided in the Prospectus.

     All authority herein conferred or agreed to be conferred by this Notice of
Guaranteed Delivery shall survive the death or incapacity of the undersigned and
every obligation of the undersigned under this Notice of Guaranteed Delivery
shall be binding upon the heirs, personal representatives, executors,
administrators, successors, assigns, trustees in bankruptcy and other legal
representatives of the undersigned.
<PAGE>

                            PLEASE SIGN AND COMPLETE

<Table>
<S>                                                                <C>
            Signature(s) of Registered Owner(s)                                  Name(s) of Registered Holder(s):
                  or Authorized Signatory:



          ----------------------------------------                           ----------------------------------------



          ----------------------------------------                           ----------------------------------------



          ----------------------------------------                           ----------------------------------------
  Principal Amount of Original Fixed Rate Notes Tendered:                                    Address:



          ----------------------------------------                           ----------------------------------------
    Certificate No(s). of Original Fixed Rate Notes (if                            Area Code and Telephone No.:
                         available):



          ----------------------------------------                  If Original Notes will be delivered by book-entry transfer
          ----------------------------------------                  at The Depository Trust Company, insert Depository Account
                                                                                               No.:
                                                                             ----------------------------------------



          ----------------------------------------
 Principal Amount of Original Floating Rate Notes Tendered:



          ----------------------------------------
   Certificate No(s). of Original Floating Rate Notes (if
                         available):



          ----------------------------------------



          ----------------------------------------



          ----------------------------------------



          ----------------------------------------
                           Date:
</Table>

     This Notice of Guaranteed Delivery must be signed by the registered
holder(s) of Original Notes exactly as its (their) name(s) appear on
certificates for Original Notes or on a security position listing as the owner
of Original Notes, or by person(s) authorized to become registered Holder(s) by
endorsements and documents transmitted with this Notice of Guaranteed Delivery.
If signature is by a trustee, executor, administrator, guardian,
attorney-in-fact, officer or other person acting in a fiduciary or
representative capacity, such person must provide the following information

                      PLEASE PRINT NAME(S) AND ADDRESS(ES)

<Table>
<S>                                                      <C>     <C>

Name(s): ---------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------

Capacity:  -------------------------------------------------------------------------------------------------------

Address(es): -----------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------
</Table>

     DO NOT SEND ORIGINAL NOTES WITH THIS FORM.  ORIGINAL NOTES SHOULD BE SENT
TO THE EXCHANGE AGENT TOGETHER WITH A PROPERLY COMPLETED AND DULY EXECUTED
LETTER OF TRANSMITTAL.
<PAGE>

                             GUARANTEE OF DELIVERY
                    (NOT TO BE USED FOR SIGNATURE GUARANTEE)

     The undersigned, a member firm of a registered national securities exchange
or of the National Association of Securities Dealers, Inc. or a commercial bank
or trust company having an office or a correspondent in the United States or an
"eligible guarantor institution" as defined by Rule 17Ad-15 under the Securities
Exchange Act of 1934, as amended, hereby (a) represents that each bolder of
Original Notes on whose behalf this tender is being made "own(s)" the Original
Notes covered hereby within the meaning of Rule 14e-4 under the Exchange Act,
(b) represents that such tender of Original Notes complies with such Rule 14e-4,
and (c) guarantees that, within three New York Stock Exchange trading days from
the date of this Notice of Guaranteed Delivery, a properly completed and duly
executed Letter of Transmittal, together with certificates representing the
Original Notes covered hereby in proper form for transfer and required documents
will be deposited by the undersigned with the Exchange Agent.

     THE UNDERSIGNED ACKNOWLEDGES THAT IT MUST DELIVER THE LETTER OF TRANSMITTAL
AND ORIGINAL NOTES TENDERED HEREBY TO THE EXCHANGE AGENT WITHIN THE TIME SET
FORTH ABOVE AND THAT FAILURE TO DO SO COULD RESULT IN FINANCIAL LOSS TO THE
UNDERSIGNED.

<Table>
<S>                                                             <C>

---------------------------------------------------------       ---------------------------------------------------------
                      NAME OF FIRM:                                               AUTHORIZED SIGNATURE




---------------------------------------------------------       ---------------------------------------------------------
                        ADDRESS:                                                          NAME:




                                                                ---------------------------------------------------------
                                                                                         TITLE:
---------------------------------------------------------




---------------------------------------------------------       ---------------------------------------------------------
               AREA CODE AND TELEPHONE NO.                                                DATE:




---------------------------------------------------------
</Table>