<PAGE>   1
                                                                  EXHIBIT 10.14
                               AMENDMENT NO. 2
                                      TO
                               CREDIT AGREEMENT

         AMENDMENT NO. 2, dated as of March 8, 2001 (this "Amendment"), to the
Credit Agreement, dated as of December 4, 2000, among Building Materials
Corporation of America (the "Borrower"), the lenders from time to time party
thereto, and The Bank of New York, as Swing Line Lender and as Administrative
Agent (in such capacity, the "Administrative Agent") (as amended to the date
hereof, the "Credit Agreement").

                                   RECITALS

         I.       Capitalized terms used herein which are not otherwise
defined herein shall have the respective meanings ascribed thereto in the
Credit Agreement.

         II.      The Borrower has requested that the Administrative Agent and
the Lenders amend the Credit Agreement upon the terms and conditions contained
in this Amendment, and the Administrative Agent and the Required Lenders are
willing so to do.

         Accordingly, in consideration of the Recitals and the covenants and
conditions hereinafter set forth, and of other good and valuable
consideration, the receipt and adequacy of which are hereby acknowledged, the
parties hereto hereby agree as follows:

         1.       Section 2.7(b) of the Credit Agreement is amended and
restated in its entirety to read as follows:

                  (b)      Mandatory Prepayments. At any time when the
         Invested Cash plus the sum of (i) the book value (as determined in
         accordance with GAAP and reflected in the most recent Consolidated
         balance sheet delivered to the Administrative Agent and the Lenders
         pursuant to Section 7.1(d)) of the City of Michigan City, Indiana
         Economic Development Taxable Revenue Bonds Series 1999 held by the
         Borrower and its Subsidiaries and (ii) the Marketable Securities of
         the Borrower and its Subsidiaries (other than any Receivables
         Subsidiary) on a Consolidated basis in accordance with GAAP exceed
         (i) for the period beginning on the Effective Date and ending 91 days
         thereafter, $25,000,000, and (ii) for the period beginning 92 days
         after the Effective Date and thereafter, $50,000,000, the Borrower
         shall immediately repay any outstanding Loans in an amount equal to
         such excess.

         2.       Section 6.3 of the Credit Agreement is amended and restated
in its entirety to read as follows:

                  6.3.     Minimum Cash Amount

<PAGE>   2

                  On each Borrowing Date and with respect to the making of
         Loans and the issuance of Letters of Credit, the Invested Cash plus
         the sum of (i) the book value (as determined in accordance with GAAP
         and reflected in the most recent Consolidated balance sheet delivered
         to the Administrative Agent and the Lenders pursuant to Section
         7.1(d)) of the City of Michigan City, Indiana Economic Development
         Taxable Revenue Bonds Series 1999 held by the Borrower and its
         Subsidiaries and (ii) the Marketable Securities of the Borrower and
         its Subsidiaries (other than any Receivables Subsidiary) on a
         Consolidated basis in accordance with GAAP shall be less than (i) for
         the period beginning on the Effective Date and ending 91 days
         thereafter, $25,000,000, and (ii) for the period beginning 92 days
         after the Effective Date and thereafter, $50,000,000.

         3.       Effective as of December 4, 2000, Schedule 8.5 to the Credit
Agreement is amended and restated in its entirety in the form of Schedule 8.5
attached hereto.

         4.       Section 3 of each of Exhibit C-1 and C-2 is amended and
restated in its entirety to read as follows:

                  3.       The Borrower hereby certifies that on the date
         hereof and on the Borrowing Date set forth above, (a) the Invested
         Cash plus the sum of (i) the book value (as determined in accordance
         with GAAP and reflected in the most recent Consolidated balance sheet
         delivered to the Administrative Agent and the Lenders pursuant to
         Section 7.1(d)) of the City of Michigan City, Indiana Economic
         Development Taxable Revenue Bonds Series 1999 held by the Borrower
         and its Subsidiaries and (ii) the Marketable Securities of the
         Borrower and its Subsidiaries (other than any Receivables Subsidiary)
         on a Consolidated basis in accordance with GAAP is less than (i) for
         the period beginning on the Effective Date and ending 91 days
         thereafter, $25,000,000, and (ii) for the period beginning 92 days
         after the Effective Date and thereafter, $50,000,000.

         5.       Paragraphs 1-4 shall not be effective until the
Administrative Agent shall have received this Amendment, duly executed by a
duly authorized officer or officers of the Borrower, the Guarantors, the
Administrative Agent and the Required Lenders.

         6.       On the date hereof, each Credit Party hereby (a) reaffirms
and admits the validity and enforceability of each Loan Document (as amended
by this Amendment) to which it is a party and all of its obligations
thereunder, (b) agrees and admits that it has no defenses to or offsets
against any such obligation, and (c) represents and warrants that no Default
or Event of Default under any Loan Document (as amended by this Amendment) has
occurred and is continuing, and that each of the representations and
warranties made by it in the Loan Documents (as amended by this Amendment) to
which it is a party is true and correct in all material respects with the same
effect as though each such representation and warranty had been made on the
date hereof, except to the extent such representation and warranty
specifically relates to an earlier date, in which case such representation and
warranty shall have been true and correct on and as of such earlier date.

                                      2

<PAGE>   3

         7.       In all other respects, the Loan Documents shall remain in
full force and effect, and no consent or amendment in respect of any term or
condition of any Loan Document contained herein shall be deemed to be a
consent or amendment in respect of any other term or condition contained in
any Loan Document.

         8.       This Amendment may be executed in any number of counterparts
all of which, taken together, shall constitute one agreement. In making proof
of this Amendment, it shall only be necessary to produce the counterpart
executed and delivered by the party to be charged. All future references to
the Credit Agreement shall mean and refer to the Credit Agreement as amended
hereby.

         9.       THIS AMENDMENT IS BEING EXECUTED AND DELIVERED IN, AND IS
INTENDED TO BE PERFORMED IN, THE STATE OF NEW YORK AND SHALL BE CONSTRUED AND
ENFORCEABLE IN ACCORDANCE WITH, AND BE GOVERNED BY, THE INTERNAL LAWS OF THE
STATE OF NEW YORK, WITHOUT REGARD TO PRINCIPLES OF CONFLICT OF LAWS, BUT
INCLUDING SECTION 5-1401 OF THE GENERAL OBLIGATIONS LAW.

                           [signature pages follow]


                                      3
<PAGE>   4

                               AMENDMENT NO. 2
                                      TO
                               CREDIT AGREEMENT
                  BUILDING MATERIALS CORPORATION OF AMERICA


         AS EVIDENCE of the agreement by the parties hereto to the terms and
conditions herein contained, each such party has caused this Amendment No. 2 to
be executed on its behalf.


                              BUILDING MATERIALS CORPORATION OF AMERICA


                              By: /s/ Susan B. Yoss
                                 -----------------------------------------
                              Name: Susan B. Yoss
                                   ---------------------------------------
                              Title: Senior Vice President and Treasurer
                                    --------------------------------------




<PAGE>   5



                               AMENDMENT NO. 2
                                      TO
                               CREDIT AGREEMENT
                  BUILDING MATERIALS CORPORATION OF AMERICA




                              THE BANK OF NEW YORK, as Swing Line Lender, as
                              Issuing Bank, as Administrative Agent and as a
                              Lender


                              By: /s/ David C. Judge
                                  -----------------------------------
                              Name: David C. Judge
                                   ----------------------------------
                              Title: Senior Vice President
                                    ---------------------------------


<PAGE>   6



                               AMENDMENT NO. 2
                                      TO
                               CREDIT AGREEMENT
                  BUILDING MATERIALS CORPORATION OF AMERICA




                              FLEET NATIONAL BANK


                              By: /s/ Peggy Peckham
                                  -----------------------------------
                              Name: Peggy Peckham
                                   ----------------------------------
                              Title: Senior Vice President
                                    ---------------------------------


<PAGE>   7




                               AMENDMENT NO. 2
                                      TO
                               CREDIT AGREEMENT
                  BUILDING MATERIALS CORPORATION OF AMERICA



                              BEAR STEARNS CORPORATE LENDING INC.


                              By: /s/ Victor F. Bulzaccehellci
                                  -----------------------------------
                              Name: Victor F. Bulzaccehellci
                                   ----------------------------------
                              Title: Managing Director
                                    ---------------------------------


<PAGE>   8



                               AMENDMENT NO. 2
                                      TO
                               CREDIT AGREEMENT
                  BUILDING MATERIALS CORPORATION OF AMERICA




                              THE CHASE MANHATTAN BANK


                              By: /s/ Peter A. Dedousis
                                  -----------------------------------
                              Name: Peter A. Dedousis
                                   ----------------------------------
                              Title: Managing Director
                                    ---------------------------------


<PAGE>   9



                               AMENDMENT NO. 2
                                      TO
                               CREDIT AGREEMENT
                  BUILDING MATERIALS CORPORATION OF AMERICA




                              THE BANK OF NOVA SCOTIA


                              By: /s/ Daniel A. Costigan
                                  -----------------------------------
                              Name: Daniel A. Costigan
                                   ----------------------------------
                              Title: Director
                                    ---------------------------------


<PAGE>   10



                               AMENDMENT NO. 2
                                      TO
                               CREDIT AGREEMENT
                  BUILDING MATERIALS CORPORATION OF AMERICA




AGREED AND CONSENTED TO:


BMCA INSULATION PRODUCTS INC.
BUILDING MATERIALS INVESTMENT CORPORATION
BUILDING MATERIALS MANUFACTURING CORPORATION
DUCTWORK MANUFACTURING CORPORATION
GAF LEATHERBACK CORP.
GAF MATERIALS CORPORATION (CANADA)
GAF PREMIUM PRODUCTS INC.
GAFTECH CORPORATION
LL BUILDING PRODUCTS INC.
WIND GAP REAL PROPERTY ACQUISITION
    CORP.


By: /s/ Susan B. Yoss
    ----------------------------------------
Name: Susan B. Yoss
      --------------------------------------
Title: Senior Vice President and Treasurer
       -------------------------------------