EXHIBIT 3.25

                            CERTIFICATE OF AMENDMENT
                                       OF
                          CERTIFICATE OF INCORPORATION

                  PVC Pipe Manufacturing Corporation ("Corporation"), a
corporation organized and existing under and by virtue of the General
Corporation Law of the State of Delaware, does hereby certify:

                  FIRST: That the Board of Directors of said corporation, by
unanimous written consent of its members, filed with the minutes of the Board,
adopted a resolution proposing and declaring advisable the following amendment
to the Certificate of Incorporation of said corporation:

                  RESOLVED, That the Certificate of Incorporation of PVC Pipe
Manufacturing Corporation be amended by changing Article I thereof so that, as
amended, said Article shall be and read as follows:

                                    ARTICLE I

                  The name of the corporation is Westech Building Products, Inc.

                  SECOND: That in lieu of a meeting and vote of stockholders,
the stockholders have given written consent to said amendment in accordance with
Section 228 of the General Corporation Law of the State of Delaware.

                  THIRD: That the aforesaid amendment was duly adopted in
accordance with the applicable provisions of Sections 242 and 228 of the General
Corporation Law of the State of Delaware.

                  IN WITNESS WHEREOF, PVC Pipe Manufacturing Corporation has
caused this certificate to be signed by its Secretary this 3rd day of May, 1996.

                                              PVC PIPE MANUFACTURING CORPORATION

                                              By: /s/ S. Clayton Snear
                                                  ------------------------------
                                                      S. Clayton Snear
                                                      Secretary