<PAGE>   1
                                 EXHIBIT (4.10)

                       FOURTH AMENDMENT TO LOAN AGREEMENT

    FOURTH AMENDMENT TO LOAN AGREEMENT (this "Fourth Amendment"), dated as of
December 15, 1997, is entered into among ELCOR CORPORATION, a Delaware
corporation ("Company"), the lenders listed on the signature pages hereof
("Lenders"), NATIONSBANK OF TEXAS, N.A., as Issuer (in said capacity, "Issuer"),
and NATIONSBANK OF TEXAS, N.A., as Administrative Lender (in said capacity,
"Administrative Lender").

                                   BACKGROUND

     A. Company, the Lenders, Issuer and Administrative Lender are parties to
that certain Loan Agreement, dated as of September 29, 1993, as amended by that
certain First Amendment to Loan Agreement, dated as of October 31, 1994, that
certain Second Amendment to Loan Agreement, dated as of December 15, 1995, and
that certain Third Amendment to Loan Agreement, dated as of October 31, 1996
(said Loan Agreement, as amended, the "Loan Agreement"; the terms defined in the
Loan Agreement and not otherwise defined herein shall be used herein as defined
in the Loan Agreement).

     B. Company, Lenders, Issuer and Administrative Lender desire to amend the
Loan Agreement to (i) increase the Commitment to $100,000,000, (ii) extend the
Termination Date, (iii) add The Bank of Tokyo-Mitsubishi, Ltd. as a Lender
thereto ("Bank of Tokyo"), and (iv) make certain other amendments thereto.

     NOW, THEREFORE, in consideration of the covenants, conditions and
agreements hereafter set forth, and for other good and valuable consideration,
the receipt and adequacy of which are all hereby acknowledged, Company, Lenders,
Issuer and Administrative Lender covenant and agree as follows:

     1. AMENDMENTS TO LOAN AGREEMENT.

        (a) The dollar amount of "$80,000,000" set forth in the Background
     paragraph of the Loan Agreement is hereby amended to be "$100,000,000".

        (b) The definition of "Commitment" set forth in Section 1.1 of the Loan
     Agreement is hereby amended to read as follows:

           "'Commitment' means as to any Lender, the amount set forth opposite
        such Lender's name under the column titled "Commitment" on Schedule 7
        hereto, as the same may be reduced or terminated pursuant to Article 2,
        which at no time shall exceed such Lender's Specified Percentage of
        $100,000,000."




<PAGE>   2

        (c) The definition of "Subsidiary" set forth in Section 1.1 of the Loan
     Agreement is hereby amended to read as follows:

           "'Subsidiary' of Company means any corporation, partnership, joint
        venture, trust or estate or other Person of which (or in which) more
        than 50% of:

            (a) the outstanding capital stock having voting power to elect a
        majority of the Board of Directors of such corporation (irrespective of
        whether at the time capital stock of any other class or classes of such
        corporation shall or might have such voting power upon the occurrence of
        any contingency),

            (b) the interest in the capital or profits of such partnership or
        joint venture,

            (c) the beneficial interest of such trust or estate, or

            (d) the equity interest of such other Person,

        is at the time directly or indirectly owned by Company, by Company and
        one or more of its Subsidiaries or by one or more of Company's
        Subsidiaries."

        (d) The definition of "Termination Date" set forth in Section 1.1 of the
     Loan Agreement is hereby amended to read as follows:

       "'Termination Date' means December 15, 2002, or such earlier date that
     the Commitment is terminated or such later date that the Commitment is
     extended pursuant to Section 2.19 hereof."

        (e) Section 2.6 of the Loan Agreement is hereby amended to read as
     follows:

            "2.6. Commitment Fee. Subject to Section 9.13 hereof, Company shall
        pay to the Administrative Lender, for the ratable account of the Lender,
        a commitment fee (which shall be payable quarterly in arrears on each
        Quarterly Date and on the Termination Date) on the daily average Unused
        Portion (as later defined in this Section 2.6) at the following per
        annum percentages, applicable in the following situations:

<TABLE>
<CAPTION>
                                      Applicability                        Fee
                                      -------------                        ---

<S>                                                                       <C>   
            (i)   If the Fixed Charge Coverage Ratio is less than 1.25    0.300 
                  to 1

            (ii)  If the Fixed Charge Coverage Ratio is greater than or   0.200
                  equal to 1.25 to 1 but less than 1.50 to 1

            (iii) If the Fixed Charge Coverage Ratio is greater than or   0.175 
                  equal to 1.50 to 1
</TABLE>



                                     - 2 -
<PAGE>   3

            The commitment fee payable hereunder shall be subject to reduction
        or increase, as applicable and as set forth in the table above, on a
        quarterly basis according to the performance of Company as tested by the
        Fixed Charge Coverage Ratio. Any such increase or reduction in such
        commitment fee shall be effective on the first calendar day of the month
        next succeeding the date of receipt by Administrative Lender of the
        applicable financial statements. If financial statements of Company
        setting forth the Fixed Charge Coverage Ratio are not received by
        Administrative Lender by the date required pursuant to Section 5.5
        hereof, the commitment fee shall be determined as if the Fixed Charge
        Coverage Ratio is less than 1.25 to 1 until such time as such financial
        statements are received. For the final quarter of any fiscal year of
        Company, Company may provide its unaudited financial statements, subject
        only to year-end adjustments, for the purpose of adjusting the
        commitment fee. The commitment fee is fully earned when due,
        non-refundable when paid, and shall be computed on the basis of 365 or
        366 days, as applicable, for the actual number of days elapsed.
        Administrative Lender is authorized to, and shall to the extent of funds
        available, debit Company's account at NationsBank Texas for the payment
        of such commitment fee after oral notice thereof is given to Company by
        Administrative Lender. As used herein, the "Unused Portion" shall mean
        an amount equal to the result of the Commitment, minus the sum of (A)
        outstanding Advances plus (B) outstanding Reimbursement Obligations."

        (f) Section 5.23 of the Loan Agreement is hereby amended to read as
     follows:

            "5.23. Guaranties by New Subsidiaries. Company shall cause each
        Subsidiary which Company or any of its Subsidiaries forms during the
        term of this Agreement to execute and deliver to Administrative Lender a
        Guaranty Agreement, together with a certified copy of a resolution of
        the board of directors (or other authorizing document of the appropriate
        governing body or Person) of such new Subsidiary authorizing the
        execution and delivery of the Guaranty Agreement and the performance of
        its terms."

        (g) Section 6.1 of the Loan Agreement is hereby amended to read as
     follows:

            "6.1. Organization and Qualification. Company and each Subsidiary
        (i) is a corporation or organization duly organized, validly existing,
        and in good, standing under the Laws of its jurisdiction of
        incorporation or organization, (ii) is duly licensed and in good
        standing as a foreign corporation or organization in each jurisdiction
        in which the nature of the business transacted or the property owned is
        such as to require licensing as such and where the failure to so qualify



                                     - 3 -
<PAGE>   4

        could reasonably be expected to result in a Material Adverse Effect; and
        (iii) possesses all requisite authority, power, licenses, permits and
        franchises to conduct its business and execute, deliver and comply with
        the terms of the Loan Papers to be executed by it, all of which have
        been duly authorized and approved by all necessary corporate or other
        legal action and for none of which is any approval or consent of any
        Tribunal required."

        (h) Section 6.5 of the Loan Agreement is hereby amended to read as
     follows:

            "6.5. Authority; Validity. The Board of Directors of Company has
        duly authorized the execution and delivery of this Agreement, the Notes
        and the other Loan Papers and the performance of their respective terms.
        The Board of Directors or other governing body or Person of each
        Subsidiary has authorized the execution and delivery of the Loan Papers
        to be executed and delivered by such Subsidiary and the performance of
        their respective terms. No consent of the stockholders or other equity
        interest owners of Company or any Subsidiary is required as a
        prerequisite to the validity and enforceability of this Agreement or any
        document contemplated herein other than those that have already been
        obtained. Company and each Subsidiary has full power, authority and
        legal right to execute and deliver and to perform and observe the
        provisions of all Loan Papers to be executed and delivered by it. This
        Agreement is, and the Notes and each of the other Loan Papers will on
        due execution and delivery thereof be, the legal, valid and binding
        obligation of the Company or the Subsidiary executing and delivering it,
        enforceable in accordance with their respective terms, subject as to
        enforcement of remedies to any Debtor Relief Laws. All Subsidiaries are
        signatories on the Guaranty or an amendment or supplement thereto, and
        their respective jurisdictions of incorporation or organization are
        correctly identified thereon."

        (i) Schedule 1 to the Loan Agreement is hereby amended and supplemented
     as set forth on Schedule 1 to this Fourth Amendment.

        (j) Schedule 4 to the Loan Agreement is hereby amended and supplemented
     as set forth on Schedule 4 to this Fourth Amendment.

        (k) Schedule 6 to the Loan Agreement is hereby amended and supplemented
     as set forth on Schedule 6 to this Fourth Amendment.

        (l) Schedule 7 to the Loan Agreement is hereby amended to be in the form
     of Schedule 7 to this Fourth Amendment, and the Specified Percentage of
     Bank of Tokyo is established and the applicable Specified Percentages of
     the other Lenders are amended as provided therein.



                                      - 4 -
<PAGE>   5

     2. REPRESENTATIONS AND WARRANTIES TRUE; NO EVENT OF DEFAULT. By its 
execution and delivery hereof, Company represents and warrants that, as of the
date hereof and after giving effect to the amendments contemplated by the
foregoing Section 1:

        (a) the representations and warranties contained in the Loan Agreement
     are true and correct on and as of the date hereof as if made on and as of
     such date;

        (b) no event has occurred and is continuing which constitutes a Default
     or an Event of Default;

        (c) Company has full power and authority to execute and deliver this
     Fourth Amendment, the $40,000,000 Note payable to the order of NationsBank
     of Texas, N.A. in the form of Exhibit A hereto (the "NationsBank Note"),
     the $30,000,000 Note payable to the order of Bank of America-Texas, N.A. in
     the form of Exhibit B hereto (the "Bank of America Note"), the $15,000,000
     Note payable to the order of Comerica Bank-Texas in the form of Exhibit C
     hereto (the, "Comerica Note"), and the $15,000,000 Note payable to the
     order of The Bank of Tokyo-Mitsubishi, Ltd. in the form of Exhibit D hereto
     (the "Bank of Tokyo Note") (the NationsBank Note, the Bank of America Note,
     the Comerica Note and the Bank of Tokyo Note are collectively referred to
     herein as the "Notes"), and this Fourth Amendment, the Loan Agreement, as
     amended hereby, and the Notes constitute the legal, valid and binding
     obligations of Company, enforceable in accordance with their respective
     terms, except as enforceability may be limited by applicable debtor relief
     laws and by general principles of equity (regardless of whether enforcement
     is sought in a proceeding in equity or at law) and except as rights to
     indemnity may be limited by federal or state securities law;

        (d) neither the execution, delivery and performance of this Fourth
     Amendment, the Notes or the Loan Agreement, as amended hereby, nor the
     consummation of any transactions contemplated herein or therein, will
     conflict with any Law to which Company or any Subsidiary is subject, or any
     indenture, agreement or other instrument to which Company or any Subsidiary
     or any of their respective property is subject; and

        (e) no authorization, approval, consent, or other action by, notice to,
     or filing with, any governmental authority or other Person (other than the
     Board of Directors of Company), is required for the execution, delivery or
     performance by Company of this Fourth Amendment or the Notes or the
     acknowledgement of this Fourth Amendment by each Subsidiary which executed
     the Guaranty Agreement (a "Guarantor").

     3. CONDITIONS OF EFFECTIVENESS. This Fourth Amendment shall be effective as
of December 15, 1997, subject to the following:




                                      - 5 -
<PAGE>   6

        (a) Administrative Lender shall have received counterparts of this
     Fourth Amendment executed by each Lender and Issuer;

        (b) Administrative Lender shall have received counterparts of this
     Fourth Amendment executed by Company and acknowledged by each Guarantor;

        (c) Each Lender shall have received its respective Note executed by
     Company;

        (d) the representations and warranties set forth in Section 2 of this
     Fourth Amendment shall be true and correct;

        (e) Administrative Lender shall have received certified copies of
     resolutions of Company authorizing execution, delivery and performance of
     this Fourth Amendment and the Notes; and

        (f) Administrative Lender shall have received, in form and substance
     satisfactory to Administrative Lender and its counsel, such other
     documents, certificates and instruments as Administrative Lender shall
     require.

     4. GUARANTORS ACKNOWLEDGEMENT. By signing below, each of the Guarantors (i)
acknowledges and consents to the execution, delivery and performance by Company
of this Fourth Amendment, (ii) agrees that its obligations in respect of the
Guaranty Agreement (A) are not released, modified, impaired or affected in any
manner by this Fourth Amendment or any of the provisions contemplated herein,
and (B) cover, among other things, the Commitment as increased by this Fourth
Amendment, and (ii) acknowledges that it has no claims or offsets against, or
defenses or counterclaims to, the Guaranty Agreement.

     5. REFERENCE TO THE LOAN AGREEMENT.

        (a) Upon the effectiveness of this Fourth Amendment, each reference in
     the Loan Agreement to "this Agreement", "hereunder", or words of like
     import shall mean and be a reference to the Loan Agreement, as affected and
     amended by this Fourth Amendment.

        (b) The Loan Agreement, as amended by this Fourth Amendment, and all
     other Loan Papers shall remain in full force and effect and are hereby
     ratified and confirmed.

     6. COSTS, EXPENSES AND TAXES. Company agrees to pay on demand all costs and
expenses of Administrative Lender in connection with the preparation,
reproduction, execution and delivery of this Fourth Amendment, the Notes, and
the other instruments and documents to be delivered hereunder (including the
reasonable fees and out-of-pocket expenses of counsel for Administrative Lender
with respect thereto and with respect to advising




                                      - 6 -
<PAGE>   7

Administrative Lender as to its rights and responsibilities under the Loan
Agreement, as amended by this Fourth Amendment).

     7. ADVANCES. Upon effectiveness of this Agreement, each of the appropriate
Lenders, through the Administrative Lender, by assignments, purchases and
adjustments (which shall occur and shall be deemed to occur automatically upon
such effectiveness), shall have purchased or sold such Advances so that after
giving effect to such assignments, purchases and adjustments, each Lender shall
hold Advances and Reimbursement Obligations in accordance with its Specified
Percentage, as established or amended hereby. The parties hereto agree that the
requirements of Section 9.1 of the Loan Agreement with respect to assignments
are hereby waived for purposes of this Fourth Amendment only. Each Lender
selling and assigning all or any portion of an Advance and Reimbursement
Obligations hereby represents and warrants that such interest being sold is free
and clear of any Lien or adverse claim. Bank of Tokyo (a) confirms that it has
received a copy of the Loan Agreement and the other Loan Papers, together with
copies of the financial statements referred to in Sections 5.5 and 6.2 of the
Loan Agreement and such other documents and information as it has deemed
appropriate to make its own credit analysis and decision to enter into this
Fourth Amendment, (b) agrees that it will, independently and without reliance
upon the Administrative Lender, or any other Lender, and based on such documents
and information as it shall deem appropriate at the time, continue to make its
own credit decisions in taking or not taking action under the Loan Agreement and
the other Loan Papers, (c) appoints and authorizes the Administrative Lender to
take such action as agent on its behalf and to exercise such powers under the
Loan Agreement and the other Loan Papers as are delegated to the Administrative
Lender by the terms thereof, together with such powers as are reasonably
incidental thereto and hereto, and (d) agrees that it will perform in accordance
with its terms all of the obligations which by the terms of the Loan Agreement,
the other Loan Papers, and this Assignment and are required to be performed by
it as a Lender.

     8. EXECUTION IN COUNTERPARTS. This Fourth Amendment may be executed in any
number of counterparts and by different parties hereto in separate counterparts,
each of which when so executed and delivered shall be deemed to be an original
and all of which taken together shall constitute but one and the same
instrument.

     9. GOVERNING LAW; BINDING EFFECT. This Fourth Amendment shall be governed
by and construed in accordance with the laws of the State of Texas and shall be
binding upon Company, each Lender, Issuer and Administrative Lender and their
respective successors and assigns.

     10. HEADINGS. Section headings in this Fourth Amendment are included herein
for convenience of reference only and shall not constitute a part of this Fourth
Amendment for any other purpose.

     11. ENTIRE AGREEMENT. THE LOAN AGREEMENT, AS AMENDED BY THIS FOURTH
AMENDMENT, AND THE OTHER LOAN PAPERS REPRESENT THE FINAL AGREEMENT BETWEEN THE
PARTIES AS TO THE SUBJECT MATTER




                                      - 7 -
<PAGE>   8
THEREIN AND HEREIN AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR,
CONTEMPORANEOUS, OR SUBSEQUENT ORAL AGREEMENTS BETWEEN THE PARTIES.

                   REMAINDER OF PAGE LEFT INTENTIONALLY BLANK






                                      - 8 -
<PAGE>   9
     IN WITNESS WHEREOF, the parties hereto have executed this Fourth Amendment
as of the date first above written.

                                        ELCOR CORPORATION


                                        By: /s/ RICHARD J. ROSEBERY
                                           ------------------------------------
                                           Richard J. Rosebery
                                           Vice Chairman, Chief Financial and
                                           Administrative Officer and Treasurer





                                      - 9 -
<PAGE>   10


                                   NATIONSBANK OF TEXAS, N.A., as
                                   Administrative Lender, Lender and Issuer

                                        By:    /s/ JASON BRUHL
                                           -----------------------------------
                                        Name:  Jason Bruhl
                                             ---------------------------------
                                        Title: Vice President
                                              --------------------------------



                                     - 10 -
<PAGE>   11

                                   BANK OF AMERICA - TEXAS, N.A.

                                        By: /s/ DONALD P. HELLMAN
                                           -----------------------------------
                                           Name:  Donald P. Hellman
                                                ------------------------------
                                           Title: Vice President
                                                 -----------------------------





                                     - 11 -
<PAGE>   12

                                   COMERICA BANK - TEXAS

                                        By: /s/ LARRY W. CALTON
                                           -----------------------------------
                                           Name:  Larry W. Calton
                                                ------------------------------
                                           Title: Assistant Vice President
                                                 -----------------------------





                                     - 12 -
<PAGE>   13

                                   THE BANK OF TOKYO-MITSUBISHI, LTD.

                                        By: /s/ CHRIS W. HOLDER
                                           -----------------------------------
                                           Name:  Chris W. Holder
                                                ------------------------------
                                           Title: Vice President
                                                 -----------------------------



                                     - 13 -
<PAGE>   14

ACKNOWLEDGED AND AGREED:

ELK CORPORATION OF DALLAS 
ELK CORPORATION OF TEXAS
ELK CORPORATION OF AMERICA 
ELK CORPORATION OF ARKANSAS 
ELK CORPORATION OF ALABAMA 
CHROMIUM CORPORATION 
OEL, LTD.

By: /s/ RICHARD J. ROSEBERY
   --------------------------------
    Richard J. Rosebery
    Vice President for all

GA INDUSTRIES CORPORATION
M MACHINERY COMPANY, 
    INCORPORATED 
    (formerly known as Mosley 
    Machinery Company, Incorporated) 
M SERVICE CORPORATION 
    (formerly known as Mosley 
    Service Corporation)


By: /s/ RICHARD J. ROSEBERY
   --------------------------------
    Richard J. Rosebery
    President for all

ELCOR SERVICE CORPORATION

By: /s/ RICHARD J. ROSEBERY
   --------------------------------
    Richard J. Rosebery
    Vice Chairman, Chief Financial and Administrative
    Officer and Treasurer




                                     - 14 -
<PAGE>   15

                                    EXHIBIT A

                                PROMISSORY NOTE

$40,000,000.00                                          Dated: December 15, 1997

     FOR VALUE RECEIVED, the undersigned, ELCOR CORPORATION, a Delaware
corporation ("Company"), hereby promises to pay to the order of NATIONSBANK OF
TEXAS, N.A. ("Lender") the principal amount of each Advance made by Lender to
Company pursuant to the Loan Agreement (as hereinafter defined). All Advances
remaining unpaid shall be repaid in full on the Termination Date. Company
promises to pay interest on the unpaid principal balance of each Advance from
the date of such Advance until said principal amount is paid in full, at the
times and at the rate or rates as specified in the Loan Agreement.

     Both principal and interest are payable in lawful money of the United
States of America to NationsBank of Texas, N.A., as Administrative Lender, at
901 Main Street, Dallas, Texas 75202, in immediately available funds. Each
Advance made by Lender to Company pursuant to the Loan Agreement and all
payments made on account of principal hereof shall be recorded by Lender and,
prior to any transfer hereof, endorsed on the grid attached hereto which is part
of this Note; provided, however, failure to make any such recordation or
endorsement shall not affect the obligations of Company hereunder or under the
Loan Agreement.

     This Note is one of the Notes referred to in, and is entitled to the
benefits of and obligations pertaining to, the Loan Agreement dated as of
September 29, 1993 (said Loan Agreement, as amended, modified or supplemented
from time to time, the "Loan Agreement") among Company, Lender, certain other
Lenders, and NationsBank of Texas, N.A., as Administrative Lender, and this Note
is a substitution for (but is not an extinguishment or novation of any
indebtedness in respect of) that certain Note of Company payable to the order of
Lender dated October 31, 1996, in the principal amount of $40,000,000.00.

     The Loan Agreement, among other things, (i) provides for the making of
Advances by Lender to Company from time to time in an aggregate amount not to
exceed at any time outstanding the U.S. dollar amount first above mentioned, the
indebtedness of Company resulting from each such Advance being evidenced by this
Note, and (ii) contains provisions for acceleration of the maturity hereof upon
the happening of certain stated events and also for prepayments on account of
principal hereof prior to the maturity hereof upon the terms and conditions
therein specified. All terms not expressly defined herein shall have the same
definitions as set forth in the Loan Agreement.

                                        ELCOR CORPORATION

                                        By:
                                           -------------------------------------
                                           Richard J. Rosebery
                                           Vice Chairman, Chief Financial and
                                           Administrative Officer and
                                           Treasurer




<PAGE>   16

                                    EXHIBIT B

                                 PROMISSORY NOTE

$30,000,000.00                                          Dated: December 15, 1997

     FOR VALUE RECEIVED, the undersigned, ELCOR CORPORATION, a Delaware
corporation ("Company"), hereby promises to pay to the order of BANK OF AMERICA-
TEXAS, N.A. ("Lender") the principal amount of each Advance made by Lender to
Company pursuant to the Loan Agreement (as hereinafter defined). All Advances
remaining unpaid shall be repaid in full on the Termination Date. Company
promises to pay interest on the unpaid principal balance of each Advance from
the date of such Advance until said principal amount is paid in full, at the
times and at the rate or rates as specified in the Loan Agreement.

     Both principal and interest are payable in lawful money of the United
States of America to NationsBank of Texas, N.A., as Administrative Lender, at
901 Main Street, Dallas, Texas 75202, in immediately available funds. Each
Advance made by Lender to Company pursuant to the Loan Agreement and all
payments made on account of principal hereof shall be recorded by Lender and,
prior to any transfer hereof, endorsed on the grid attached hereto which is part
of this Note; provided, however, failure to make any such recordation or
endorsement shall not affect the obligations of Company hereunder or under the
Loan Agreement.

     This Note is one of the Notes referred to in, and is entitled to the
benefits of and obligations pertaining to, the Loan Agreement dated as of
September 29, 1993 (said Loan Agreement, as amended, modified or supplemented
from time to time, the "Loan Agreement") among Company, Lender, certain other
Lenders, and NationsBank of Texas, N.A., as Administrative Lender, and this Note
is a substitution for (but is not an extinguishment or novation of any
indebtedness in respect of) that certain Note of Company payable to the order of
Lender dated October 31, 1996 in the principal amount of $25,000,000.00.

     The Loan Agreement, among other things, (i) provides for the making of
Advances by Lender to Company from time to time in an aggregate amount not to
exceed at any time outstanding the U.S. dollar amount first above mentioned, the
indebtedness of Company resulting from each such Advance being evidenced by this
Note, and (ii) contains provisions for acceleration of the maturity hereof upon
the happening of certain stated events and also for prepayments on account of
principal hereof prior to the maturity hereof upon the terms and conditions
therein specified. All terms not expressly defined herein shall have the same
definitions as set forth in the Loan Agreement.

                                        ELCOR CORPORATION

                                        By:
                                           ------------------------------------
                                           Richard J. Rosebery
                                           Vice Chairman, Chief Financial and
                                           Administrative Officer and Treasurer


<PAGE>   17

                                    EXHIBIT C

                                 PROMISSORY NOTE

$15,000,000.00                                          Dated: December 15, 1997

     FOR VALUE RECEIVED, the undersigned, ELCOR CORPORATION, a Delaware
corporation ("Company"), hereby promises to pay to the order of COMERICA BANK -
TEXAS ("Lender") the principal amount of each Advance made by Lender to Company
pursuant to the Loan Agreement (as hereinafter defined). All Advances remaining
unpaid shall be repaid in full on the Termination Date. Company promises to pay
interest on the unpaid principal balance of each Advance from the date of such
Advance until said principal amount is paid in full, at the times and at the
rate or rates as specified in the Loan Agreement.

     Both principal and interest are payable in lawful money of the United
States of America to NationsBank of Texas, N.A., as Administrative Lender, at
901 Main Street, Dallas, Texas 75202, in immediately available funds. Each
Advance made by Lender to Company pursuant to the Loan Agreement and all
payments made on account of principal hereof shall be recorded by Lender and,
prior to any transfer hereof, endorsed on the grid attached hereto which is part
of this Note; provided, however, failure to make any such recordation or
endorsement shall not affect the obligations of Company hereunder or under the
Loan Agreement.

     This Note is one of the Notes referred to in, and is entitled to the
benefits of and obligations pertaining to, the Loan Agreement dated as of
September 29, 1993 (said Loan Agreement, as amended, modified or supplemented
from time to time, the "Loan Agreement") among Company, Lender, certain other
Lenders, and NationsBank of Texas, N.A., as Administrative Lender, and this Note
is a substitution for (but is not an extinguishment or novation of any
indebtedness in respect of) that certain Note of Company payable to the order of
Lender dated October 31, 1996 in the principal amount of $15,000,000.00.

     The Loan Agreement, among other things, (i) provides for the making of
Advances by Lender to Company from time to time in an aggregate amount not to
exceed at any time outstanding the U.S. dollar amount first above mentioned, the
indebtedness of Company resulting from each such Advance being evidenced by this
Note, and (ii) contains provisions for acceleration of the maturity hereof upon
the happening of certain stated events and also for prepayments on account of
principal hereof prior to the maturity hereof upon the terms and conditions
therein specified. All terms not expressly defined herein shall have the same
definitions as set forth in the Loan Agreement.

                                        ELCOR CORPORATION

                                        By:
                                           ------------------------------------
                                           Richard J. Rosebery
                                           Vice Chairman, Chief Financial and
                                           Administrative Officer and Treasurer




<PAGE>   18

                                    EXHIBIT D

                                 PROMISSORY NOTE

$15,000,000.00                                          Dated: December 15, 1997

     FOR VALUE RECEIVED, the undersigned, ELCOR CORPORATION, a Delaware
corporation ("Company"), hereby promises to pay to the order of THE BANK OF
TOKYO-MITSUBISHI, LTD. ("Lender") the principal amount of each Advance made by
Lender to Company pursuant to the Loan Agreement (as hereinafter defined). All
Advances remaining unpaid shall be repaid in full on the Termination Date.
Company promises to pay interest on the unpaid principal balance of each Advance
from the date of such Advance until said principal amount is paid in full, at
the times and at the rate or rates as specified in the Loan Agreement.

     Both principal and interest are payable in lawful money of the United
States of America to NationsBank of Texas, N.A., as Administrative Lender, at
901 Main Street, Dallas, Texas 75202, in immediately available funds. Each
Advance made by Lender to Company pursuant to the Loan Agreement and all
payments made on account of principal hereof shall be recorded by Lender and,
prior to any transfer hereof, endorsed on the grid attached hereto which is part
of this Note; provided, however, failure to make any such recordation or
endorsement shall not affect the obligations of Company hereunder or under the
Loan Agreement.

     This Note is one of the Notes referred to in, and is entitled to the
benefits of and obligations pertaining to, the Loan Agreement dated as of
September 29, 1993 (said Loan Agreement, as amended, modified or supplemented
from time to time, the "Loan Agreement") among Company, Lender, certain other
Lenders, and NationsBank of Texas, N.A., as Administrative Lender.

     The Loan Agreement, among other things, (i) provides for the making of
Advances by Lender to Company from time to time in an aggregate amount not to
exceed at any time outstanding the U.S. dollar amount first above mentioned, the
indebtedness of Company resulting from each such Advance being evidenced by this
Note, and (ii) contains provisions for acceleration of the maturity hereof upon
the happening of certain stated events and also for prepayments on account of
principal hereof prior to the maturity hereof upon the terms and conditions
therein specified. All terms not expressly defined herein shall have the same
definitions as set forth in the Loan Agreement.

                                        ELCOR CORPORATION

                                        By:
                                           ------------------------------------
                                           Richard J. Rosebery
                                           Vice Chairman, Chief Financial and
                                           Administrative Officer and Treasurer




<PAGE>   19

                                   SCHEDULE 1

                               EXISTING LITIGATION

               This schedule is confidential and has been omitted.



<PAGE>   20

                                   SCHEDULE 4

                           FIXED ASSETS HELD FOR SALE

               This schedule is confidential and has been omitted.



<PAGE>   21

                                   SCHEDULE 6

NATIONSBANK OF TEXAS, N.A.
901 Main Street
Dallas, Texas 75202

COMERICA BANK - TEXAS
1300 Northpark Center
Dallas, Texas 75225

BANK OF AMERICA TEXAS, N.A.
1925 West John Carpenter Freeway
Irving, Texas 75063

THE BANK OF TOKYO-MITSUBISHI, LTD.
3150 Trammell Crow Center
2001 Ross Avenue
Dallas, Texas 75201




<PAGE>   22

                                   SCHEDULE 7

<TABLE>
<CAPTION>
          LENDER                            COMMITMENT       SPECIFIED
          ------                            ----------       ---------
                                                             PERCENTAGE
                                                             ----------

<S>                                         <C>               <C>   
NationsBank of Texas, N.A.                  $40,000,000       40.00%

Bank of America - Texas, N.A.               $30,000,000       30.00%

Comerica Bank - Texas                       $15,000,000       15.00%

The Bank of Tokyo-Mitsubishi, Ltd.          $15,000,000       15.00%
</TABLE>