<PAGE>

                                                                   Exhibit 10.29

                                JOINDER AGREEMENT

         THIS JOINDER AGREEMENT (this "AGREEMENT"), dated as of May 7, 1999, is
executed by BANK OF AMERICA NATIONAL TRUST AND SAVINGS ASSOCIATION, a national
banking association ("ADDITIONAL BANK"), in favor of the parties to the Credit
Agreement referred to in RECITAL A below.

                                    RECITALS

         A. Pursuant to a Third Amended and Restated Credit Agreement effective
as of September 30, 1998 and amended by Amendment No. 1 thereto dated as of
March 31, 1999 (as further amended, supplemented or restated from time to time,
the "CREDIT AGREEMENT"), among BMC West Corporation, a Delaware corporation
("BORROWER"), the financial institutions from time to time parties thereto
(collectively, the "BANKS"), and Wells Fargo Bank, National Association, as
agent for the Banks (in such capacity, "AGENT"), the Banks have agreed to extend
certain credit facilities to Borrower upon the terms and subject to the
conditions set forth therein.

         B. Additional Bank will become a party to the Credit Agreement with
certain rights and obligations thereunder and under the other Credit Documents
upon the terms and subject to the conditions set forth in this Agreement.

         NOW, THEREFORE, in consideration of the above recitals and for other
good and valuable consideration, the receipt and adequacy of which are hereby
acknowledged, Additional Bank hereby agrees as follows:

         1. DEFINITIONS. Capitalized terms used but not defined in this
Agreement shall have the meanings set forth in the Credit Agreement.

         2. AGREEMENT TO BE BOUND BY CREDIT AGREEMENT. Effective on the
Effective Date (as defined in SECTION 3 below), Additional Bank hereby (a)
accepts and assumes all rights and obligations under the Credit Documents of a
Bank with the Commitment set forth on ATTACHMENT 1 hereto, including the portion
of Revolving Loans and participations in the Letters of Credit outstanding on
the Effective Date and commitments to purchase participations in Letters of
Credit that are attributable to such Commitment (the "ASSUMED RIGHTS AND
Obligations"), (b) agrees to be bound by the Credit Agreement as it would have
been if it had been an original Bank party thereto, and (c) agrees to perform in
accordance with their terms all of the obligations which are required under the
Credit Documents to be performed by it as a Bank. Additional Bank appoints and
authorizes Agent to take such actions as agent on its behalf and to exercise
such powers under the Credit Documents as are delegated to Agent by the terms
thereof, together with such powers as are reasonably incidental thereto.

         3. EFFECTIVENESS. Subject to receipt by Agent of the payments described
in SECTION 4, this Agreement shall become effective on May 7, 1999 (the
"EFFECTIVE DATE").

         4. PAYMENTS ON EFFECTIVE DATE. In consideration of the Assumed Rights
and Obligations, on the Effective Date Additional Bank shall pay to Agent for
distribution to each other Bank: (a) the principal amount of the Revolving Loans
made by such other Bank pursuant to the Credit Agreement and outstanding on the
Effective Date that are greater than such other 

<PAGE>

Bank's Proportionate Share of all Revolving Loans as determined on the Effective
Date, and (b) the amount of all Drawing Payments for which such other Bank has
reimbursed Issuing Bank that are outstanding on the Effective Date and are
greater than such other Bank's Proportionate Share of all Drawing Payments as
determined on the Effective Date.

         5. ALLOCATION AND PAYMENT OF INTEREST AND FEES. Agent shall pay to
Additional Bank all interest, commitment fees and other amounts that are paid by
or on behalf of Borrower pursuant to the Credit Documents and are attributable
to the Assumed Rights and Obligations, that accrue on and after the Effective
Date.

         6. REPRESENTATIONS AND WARRANTIES. Additional Bank represents and
warrants to Agent and the other Banks as follows:

                  (a) It has full power and authority, and has taken all action
         necessary, to execute and deliver this Agreement and to fulfill its
         obligations under, and to consummate the transactions contemplated by,
         this Agreement.

                  (b) The making and performance of this Agreement and all
         documents required to be executed and delivered by it hereunder do not
         and will not violate any law or regulation applicable to it.

                  (c) This Agreement has been duly executed and delivered by it
         and constitutes its legal, valid and binding obligation, enforceable in
         accordance with its terms.

                  (d) All approvals, authorizations or other actions by, or
         filings with, any governmental authority necessary for the validity or
         enforceability of its obligations under this Agreement have been made
         or obtained.

                  (e) Additional Bank has made and shall continue to make its
         own independent investigation of the financial condition, affairs and
         creditworthiness of Borrower and any other Person obligated under the
         Credit Documents (collectively, "CREDIT PARTIES"), and the value of any
         collateral now or hereafter securing any of the obligations,
         indebtedness, liabilities or undertakings under the Credit Documents
         ("COLLATERAL"), in connection with its assumption of the Assumed Rights
         and Obligations.

                  (f) Additional Bank has received a copy of the Credit
         Documents and such other documents, financial statements and
         information as it has deemed appropriate to make its own credit
         analysis and decision to enter into this Agreement.

                                       2
<PAGE>

         7. NO RESPONSIBILITY BY AGENT OR OTHER BANKS. Neither Agent nor any
other Bank makes any representation or warranty or assumes any responsibility to
Additional Bank for:

                  (a) the execution (by any party other than such party),
         effectiveness, genuineness, validity, enforceability, collectibility or
         sufficiency of the Credit Documents or for any representations,
         warranties, recitals or statements made in the Credit Documents or in
         any financial or other written or oral statement, instrument, report,
         certificate or any other document made or furnished or made available
         to Additional Bank by such party or by or on behalf of any Credit Party
         in connection with the Credit Documents and the transactions
         contemplated thereby;

                  (b) the performance or observance of any of the terms,
         conditions, provisions, covenants or agreements contained in any of the
         Credit Documents or as to the existence or possible existence of any
         Default or Event of Default under the Credit Documents, but this shall
         not relieve Agent of any obligation under the Credit Agreement to
         deliver notice of such Default or Event of Default; or

                  (c) the accuracy or completeness of any information provided
         to Additional Bank, whether by such party or by or on behalf of any
         Credit Party.

Neither Agent nor any other Bank shall have any initial or continuing duty or
responsibility to make any investigation of the financial condition, affairs or
creditworthiness of any of the Credit Parties, or the value of any Collateral,
in connection with Additional Bank's assumption of the Assumed Rights and
Obligations or to provide Additional Bank with any credit or other information
with respect thereto, whether coming into its possession before the date hereof
or at any time or times thereafter, except as otherwise expressly provided in
the Credit Agreement.

         8. FOREIGN WITHHOLDING. On or before the Effective Date, Additional
Bank shall comply with the provisions of SUBPARAGRAPH 2.10(b) OF THE CREDIT
AGREEMENT.

         9. GENERAL.

                  (a) This Agreement constitutes the entire understanding with
         respect to the subject matter hereof and supersedes all prior and
         current understandings and agreements, whether written or oral.

                  (b) No term or provision of this Agreement may be amended,
         waived or terminated orally, but only by an instrument signed by
         Additional Bank, Borrower, Agent and Issuing Bank.

                  (c) This Agreement may be executed in one or more
         counterparts. Each set of executed counterparts shall be an original.
         Executed counterparts may be delivered by facsimile transmission.

                  (d) This Agreement shall be binding upon and inure to the
         benefit of Additional Bank and the other parties to the Credit
         Agreement and their respective successors and assigns. Additional Bank
         may not assign or transfer any of its rights or obligations under this
         Agreement without the prior written consent of Borrower, Agent, 

                                       3
<PAGE>

         Issuing Bank and the Required Banks. The preceding sentence shall not
         limit the right of Additional Bank to grant to others assignments of or
         participations in all or part of the Assumed Rights and Obligations to
         the extent permitted by the terms of the Credit Documents.

                  (e) All payments by or to Additional Bank hereunder shall be
         made in United States Dollars, in immediately available funds. Payments
         by Additional Bank hereunder shall be made to Agent to the address or
         account specified in the Credit Agreement. Payments to Additional Bank
         shall be made to the address or account specified on ATTACHMENT 1 to
         this Agreement. The address of Additional Bank for notice purposes
         under the Credit Agreement shall be as specified on ATTACHMENT 1 to
         this Agreement.

                  (f) If any provision of this Agreement is held invalid,
         illegal or unenforceable, the remaining provisions hereof will not be
         affected or impaired in any way.

                  (g) Additional Bank shall bear its own expenses in connection
         with the preparation and execution of this Agreement.

                  (h) This Agreement shall be governed by and construed in
         accordance with the laws of the State of California.







                                       4
<PAGE>

         IN WITNESS WHEREOF, Additional Bank has executed this Agreement as of
the date first above written.

ADDITIONAL BANK:                    BANK OF AMERICA NATIONAL TRUST AND
                                    SAVINGS ASSOCIATION

                                    By: /s/ KEVIN LEADER
                                       ----------------------------------------
                                    Printed Name: Kevin Leader

                                    Title: Vice President

ACKNOWLEDGED AND AGREED:

         BORROWER:                  BMC WEST CORPORATION

                                    By: /s/ ELLIS C. GOEBEL
                                       ----------------------------------------
                                    Printed Name: Ellis C. Goebel

                                    Title: Senior VP - Finance and Treasurer



         AGENT:                     WELLS FARGO BANK, NATIONAL
                                    ASSOCIATION, as Agent

                                    By: /s/ALFRED ARTIS AND DONALD. A. HARTMANN
                                       ----------------------------------------
                                    Printed Name: Alfred Artis

                                    Title: Vice President

                                    Printed Name:  Donald A. Hartmann

                                    Title:  Vice President



         ISSUING BANK:              WELLS FARGO BANK, NATIONAL
                                    ASSOCIATION, as Issuing Bank

                                    By: /s/ALFRED ARTIS AND DONALD. A. HARTMANN
                                       ----------------------------------------
                                    Printed Name: Alfred Artis

                                    Title: Vice President

                                    Printed Name:  Donald A. Hartmann

                                    Title:  Vice President




                                       5
<PAGE>

                                 ATTACHMENT 1 TO
                                JOINDER AGREEMENT

<TABLE>
<CAPTION>

       BANK                                                                   Commitment             Commitment 
                                                                                Before              On and After 
                                                                               Scheduled             Scheduled
                                                                            Reduction Date         Reduction Date
                                                                            --------------         --------------
<S>                                                                       <C>                    <C>
D.     Bank of America National Trust and Savings Association                 $25,000,000           $25,000,000

</TABLE>

       Applicable Lending Office and Address for Notices:

           Bank of America National Trust and Savings Association
           555 California Street, 41st Floor
           San Francisco, CA  94104
           Attention:  Kevin C. Leader
           Telephone No.:  (415) 622-8168
           Telecopy No.:   (415) 622-4585
           Wiring Instructions:
           Bank of America National Trust and Savings Association
           1850 Gateway Boulevard
           Concord, CA  94520
           Attention: [                         ]
           Telephone No.: [                         ]
           Telecopy No.: [                        ]
           ABA # 121000358
           Account No.:  [                           ]
           Ref:  BMC West













                                       6