<PAGE>
                                                                  Exhibit 10.22

                 AMENDMENT NO. 1 TO THE STOCK PURCHASE AGREEMENT


          THIS AMENDMENT NO. 1 TO THE STOCK PURCHASE AGREEMENT,  is entered into
as of August 28, 2003 (this  "Amendment"),  by and among the stockholders listed
as the GENSTAR  STOCKHOLDERS  on Schedule I to the Agreement (as defined  below)
(the  "Genstar  Stockholders"),  the ONTARIO  TEACHERS'  PENSION  PLAN BOARD,  a
non-share capital corporation organized and existing under the Teachers' Pension
Act R.S.C. 1990, C.T.I.  (Ontario) ("OTPPB"),  and the other stockholders listed
on  Schedule I to the  Agreement  (together  with the Genstar  Stockholders  and
OTPPB,   collectively,   "Sellers"  and  each,  a  "Seller"),  as  sellers,  the
Sherwin-Williams  Claims Trust, a statutory  trust  organized and existing under
the laws of the State of Delaware (the "Sherwin-Williams Claims Trust"), GENSTAR
CAPITAL CORPORATION,  a corporation organized and existing under the laws of the
Province of Alberta,  Canada ("Genstar"),  as sellers'  representative  (Genstar
acting in such  capacity  or such other  Person as may  succeed  Genstar in such
capacity  being  referred to herein as "Sellers'  Representative")  and Managing
Trustee of the Sherwin-Williams Claims Trust (Genstar acting in such capacity or
such other  Person as may succeed  Genstar in such  capacity  being  referred to
herein  as  the  "Managing  Trustee"),  GENTEK  HOLDINGS,  INC.,  a  corporation
organized  and  existing  under  the  laws of the  State  of  Delaware  ("Gentek
Holdings"), GENTEK BUILDING PRODUCTS, INC., a corporation organized and existing
under  the laws of the  State  of  Delaware  ("Gentek  U.S."),  GENTEK  BUILDING
PRODUCTS  LIMITED,  a corporation  organized and existing  under the laws of the
Province  of  Ontario,   Canada  ("Gentek  Canada"),  and  ASSOCIATED  MATERIALS
INCORPORATED,  a corporation  organized and existing under the laws of the State
of Delaware ("Purchaser"), as purchaser.

                              W I T N E S S E T H:

          WHEREAS,  Sellers,  the  Sherwin-Williams  Claims  Trust,  Genstar (as
Sellers'  Representative  and Managing Trustee),  Gentek Holdings,  Gentek U.S.,
Gentek  Canada  and  Purchaser  are  parties  to  that  certain  Stock  Purchase
Agreement, entered into as of July 31, 2003 (the "Agreement").

          WHEREAS,  pursuant  to Section  11.08 of the  Agreement,  the  parties
thereto and hereto desire to amend the Agreement on the terms and subject to the
conditions set forth herein.

          NOW,  THEREFORE,  in consideration of the foregoing and the respective
agreements, covenants,  representations and warranties hereinafter set forth and
other good and  valuable  consideration,  the receipt and  adequacy of which are
hereby  acknowledged,  and  intending to be legally  bound  hereby,  the parties
hereto hereby agree as follows:

<PAGE>

          1.  Defined  Terms.  Capitalized  terms used herein but not  otherwise
defined have the meanings assigned to them in the Agreement.

          2.  Amendments to the Preamble of the  Agreement.  The preamble to the
Agreement is hereby amended as follows:

          (a) The phrase "the  Sherwin-Williams  Claims Trust, a trust organized
and existing under that certain Trust  Agreement,  dated as of July 31, 2003, by
and among  Genstar  Capital  Corporation  and the  persons  listed on Schedule I
thereto (the "Sherwin-Williams Claims Trust")" is hereby deleted and replaced by
the phrase "the  Sherwin-Williams  Claims Trust, a statutory trust organized and
existing under the laws of the State of Delaware (the  "Sherwin-Williams  Claims
Trust")".

          (b) The phrase  "(Genstar acting in such capacity or such other Person
as may  succeed  Genstar  in such  capacity  being  referred  to  herein  as the
"Trustee")"  is hereby  deleted and replaced by the phrase  "(Genstar  acting in
such capacity or such other Person as may succeed Genstar in such capacity being
referred to herein as the "Managing Trustee")".  Except as otherwise provided in
Section 3(b) of this Amendment, each reference to the "Trustee" in the Agreement
is hereby deleted and replaced by a reference to the "Managing Trustee".

          3.  Amendment  to Section 1.01 of the  Agreement.  Section 1.01 of the
Agreement is hereby amended as follows:

          (a) The  following  definition  is hereby added to Section 1.01 of the
Agreement in  alphabetical  order:  ""Managing  Trustee"  shall have the meaning
specified in the preamble to this Agreement."

          (b) The definition of "Trustee" is hereby deleted in its entirety.

          4. Amendment to Heading of Section 2.05 of the  Agreement.  The phrase
", the  Sherwin-Williams  Claims  Trust and Sellers'  Representative"  is hereby
inserted  immediately after the word "Sellers" in the heading of Section 2.05 of
the Agreement.

          5. Amendment to Section 2.05(iv) of the Agreement. Section 2.05(iv) of
the  Agreement  is hereby  amended  and  restated  in its  entirety  as follows:
"counterparts,  executed by  Sellers'  Representative  and the  Sherwin-Williams
Claims Trust, of the Escrow Agreement dated as of the Closing Date;".

          6. Amendment to Section  2.06(i) of the Agreement.  Section 2.06(i) of
the  Agreement  is hereby  amended  and  restated  in its  entirety  as follows:
"[Intentionally Omitted];".


<PAGE>

          7.  Amendment  to  Section  2.09(b)(i)  of the  Agreement.  The phrase
"thirty (30)  calendar  days" in Section  2.09(b)(i)  of the Agreement is hereby
deleted and replaced by the phrase "thirty one (31) calendar days".

          8. Amendment to Section  3.01(c) of the  Agreement.  The following two
sentences  are  hereby  inserted  at the  beginning  of  Section  3.01(c) of the
Agreement  "The  Sherwin-Williams   Claims  Trust  is  a  statutory  trust  duly
organized,  validly existing and in good standing under the laws of the State of
Delaware.  A certificate  of conversion to statutory  trust and a certificate of
trust  have  been  duly  filed in  proper  form in the name and on behalf of the
Sherwin-Williams  Claims  Trust  with the  Secretary  of  State of the  State of
Delaware and have become  effective in  accordance  with the Delaware  Statutory
Trust Act.".

          9.  Amendment to Section 6.12 of the  Agreement.  The phrase "and that
certain  Promissory  Note between Charles Canning and Gentek U.S. dated February
11, 1997, as revised  pursuant to that certain  Revision to Term Promissory Note
dated April 6, 1998" is hereby inserted  immediately before the end of the first
parenthetical of Section 6.12 of the Agreement.

          10. Amendment to Schedule III of the Agreement. Item 8 of Schedule III
to the  Agreement is hereby  deleted and replaced by the phrase  "[Intentionally
Omitted.]".

          11.  Continuing  Effect of the  Agreement.  This  Amendment  shall not
constitute a waiver,  amendment or  modification  of any other  provision of the
Agreement  not  expressly  referred  to herein and shall not be  construed  as a
waiver or  consent  to any  further  or future  action on the part of any of the
parties  that would  require a waiver or consent of the other  party.  Except as
expressly  amended or modified  herein,  the provisions of the Agreement are and
shall remain in full force and effect.

          12.  Counterparts.  This  Amendment  may be  executed  in one or  more
counterparts,  each of which shall be deemed an original, and all of which shall
constitute one and the same agreement.

          13. Governing Law; Jurisdiction.

          (a) This Amendment shall be governed by, and construed and enforced in
accordance with, the laws of the state of Delaware.

          (b) Any judicial proceeding brought against any of the parties to this
Amendment in connection  with any dispute  arising out of this  Amendment or the
transactions  contemplated  hereby (each, a "Proceeding")  may be brought in the
courts of the State of New York, or in the United States  District Court for the
Southern District of New York, and, by execution and delivery of this Amendment,
each of the parties to this Amendment accepts the exclusive jurisdiction of such
courts,  and irrevocably  agrees to be bound by any judgment rendered thereby in
connection with this Amendment.  The


<PAGE>

foregoing  consent to  jurisdiction  shall not  constitute  general  consents to
service of process in the State of New York for any  purpose  except as provided
above and shall not be deemed  to confer  rights on any  Person  other  than the
respective   parties  to  this   Amendment.   Each  of  the  Sellers,   Sellers'
Representative and Purchaser agree that service of any process,  summons, notice
or document by U.S.  registered mail to such party's address as set forth in the
Agreement  shall  be  effective  service  of  process  for any  action,  suit or
proceeding in the State of New York with respect to any Proceeding.

          14.  WAIVER OF JURY TRIAL.  EACH OF THE PARTIES  HERETO  WAIVES TO THE
FULLEST  EXTENT  PERMITTED BY  APPLICABLE  LAW ANY RIGHT IT MAY HAVE TO TRIAL BY
JURY IN  RESPECT OF ANY CLAIM,  DEMAND,  ACTION OR CAUSE OF ACTION  BASED ON, OR
ARISING OUT OF, UNDER OR IN  CONNECTION  WITH THIS  AGREEMENT,  OR ANY COURSE OF
CONDUCT,  COURSE OF DEALING,  VERBAL OR WRITTEN STATEMENT OR ACTION OF ANY PARTY
HERETO, IN EACH CASE WHETHER NOW EXISTING OR HEREAFTER  ARISING,  AND WHETHER IN
CONTRACT,  TORT,  EQUITY OR OTHERWISE.  EACH OF THE PARTIES HERETO HEREBY AGREES
THAT ANY SUCH CLAIM, DEMAND, ACTION OR CAUSE OF ACTION SHALL BE DECIDED BY COURT
TRIAL  WITHOUT  A JURY  AND  THAT  THE  PARTIES  HERETO  MAY  FILE  AN  ORIGINAL
COUNTERPART  OF A COPY OF THIS  AGREEMENT  WITH  ANY  COURT AS  EVIDENCE  OF THE
CONSENT OF THE PARTIES HERETO TO THE WAIVER OF THEIR RIGHT TO TRIAL BY JURY.




                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

<PAGE>

          IN WITNESS WHEREOF, each party hereto has executed, or caused its duly
authorized  officer(s) to execute,  this  Agreement as of the date first written
above.

                                     SELLERS

                                     THE MANUFACTURERS LIFE
                                     INSURANCE COMPANY

                                     439246 ONTARIO INC.

                                     ROYAL TRUST CORPORATION OF
                                     CANADA, TRUSTEE FOR DUPONT
                                     CANADA INC. PENSION TRUST FUND

                                     FIDUCIE DESJARDINS, COMPTE #43-
                                     00418-7 FOR SOCIETE DE TRANSPORT
                                     DE LA COMMUNAUTE URBAINE DE
                                     MONTREAL

                                     COMINCO PENSION FUND CO-
                                     ORDINATING SOCIETY

                                     GREAT-WEST LIFE & ANNUITY
                                     INSURANCE COMPANY

                                     ASSOCIATION DE BIENFAISANCE ET
                                     DE RETRAITE DES POLICIERS DE LA
                                     COMMUNAUTE URBAINE DE
                                     MONTREAL

                                     THE RETIREMENT PLAN FOR
                                     EMPLOYEES OF CANADIAN UTILITIES
                                     LIMITED AND PARTICIPATING
                                     COMPANIES PLAN I

                                     BANTOR COMPANY

                                     CROWN LIFE INSURANCE COMPANY

                                     DESJARDINS FINANCIAL SECURITY
                                     LIFE ASSURANCE COMPANY

                                     OEFC PRIVATE EQUITY HOLDCO INC.

                                     AXA SECONDARY FUND LP

<PAGE>

                                     PAUL CAPITAL PARTNERS VI
                                     HOLDINGS

                                     BPO PROPERTIES LTD.

                                     SUN LIFE ASSURANCE COMPANY OF
                                     CANADA

                                     CITIBANK CANADA

                                     CAPITAL GUIDANCE (PLACEMENTS)
                                     LTD.

                                     DAVID H. BUTTERFIELD

                                     RICHARD USHER-JONES

                                     RAYQUEST HOLDINGS LTD.

                                     MANFRED WIRTH

                                     BMO NESBITT BURNS INC.

                                     TOW PARTNERS, A CALIFORNIA
                                     LIMITED PARTNERSHIP

                                     G.R. DAWSON HOLDINGS LIMITED

                                     INVENTURES CAPITAL

                                     805491 ONTARIO INC.

                                     ZURI-INVEST A.G.

                                     ALDERPRISE INC.

                                     DAVID L. ANDERSON

                                     TERRY A. JACKSON

                                     PATHONIC ULC

                                     G. LEONARD BAKER, JR.

                                     JIC

                                     WIRRAL BOROUGH COUNCIL
                                     MERCEYSIDE PENSION FUND

<PAGE>

                                     GE CAPITAL EQUITY INVESTMENT
                                     LTD.

                                     NORTH BAY LIMITED

                                     ABN AMRO VENTURES BV

                                     GENSTAR INVESTMENT
                                     CORPORATION

                                     RICHARDSON VENTURES INC.

                                     ONTARIO TEACHERS' PENSION PLAN
                                     BOARD

                                     DAVID L. BURKE

                                     KONG H. CHEN

                                     GEORGE E. ECKERD

                                     J. HERBERT GAUL, JR.

                                     JOSEPH P. IPPOLITO

                                     DARVIN L. KING

                                     STEPHEN L. KLEIN

                                     ALAIN LAROSE

                                     JEFFREY V. MILLER

                                     MICHAEL C. MILLER

                                     WAYNE G. PALMER

                                     JAN P. RANDLES

                                     ALAIN ROBITAILLE

                                     DONALD L. SPERRY

                                     DANIEL R. TAYLOR

                                     DENNIS M. THOMPSON

<PAGE>

                                     JOHN UMIASTOWSKI

                                     By: Genstar Capital Corporation, as
                                         Sellers' Representative


                                              By: /s/ William MacDonald
                                              Name:   William MacDonald
                                              Title:  Chairman and President



                                     THE SHERWIN-WILLIAMS CLAIMS
                                     TRUST


                                     SHERWIN-WILLIAMS CLAIMS TRUST

                                     By:  Genstar Capital Corporation, as
                                          Managing Trustee


                                              By: /s/ William MacDonald
                                              Name:   William MacDonald
                                              Title:  Chairman and President

                                     SELLERS' REPRESENTATIVE

                                     GENSTAR CAPITAL CORPORATION


                                              By: /s/ William MacDonald
                                              Name:   William MacDonald
                                              Title:  Chairman and President



                                     GENTEK HOLDINGS

                                     GENTEK HOLDINGS, INC.


                                              By: /s/ Mark A. Gamble
                                              Name:   Mark A. Gamble
                                              Title:  Executive Vice President
                                                      and Chief Financial
                                                      Officer

<PAGE>

                                     GENTEK U.S.

                                     GENTEK BUILDING PRODUCTS, INC.


                                              By: /s/ Mark A. Gamble
                                              Name:   Mark A. Gamble
                                              Title:  Executive Vice President
                                                      and Chief Financial
                                                      Officer


                                     GENTEK CANADA

                                     GENTEK BUILDING PRODUCTS LIMITED


                                              By:  /s/ Mark A. Gamble
                                              Name:    Mark A. Gamble
                                              Title:   Executive Vice President
                                                       and Chief Financial
                                                       Officer



                                     PURCHASER

                                     ASSOCIATED MATERIALS INCORPORATED


                                              By: /s/ D. Keith LaVanway
                                              Name:   D. Keith LaVanway
                                              Title:  Vice President, Chief
                                                      Financial Officer,
                                                      Treasurer and Secretary