<PAGE>   1
                                                                   EXHIBIT 10.43




                       THIRD AMENDMENT TO CREDIT AGREEMENT

         THIS THIRD AMENDMENT TO CREDIT AGREEMENT (this "Amendment") is entered
into as of the 20th day of November, 2000, by and among the banks listed on the
signature pages hereof (the "Lenders"), KEVCO, INC., a Texas corporation (the
"Borrower"), and BANK OF AMERICA, N.A., formerly known as NationsBank, N.A., as
administrative agent for the Lenders (the "Administrative Agent"), to the extent
and in the manner provided for in the Credit Agreement (defined below and herein
so called).

                                   BACKGROUND

                  (a) The Lenders, the Borrower, and the Administrative Agent
         are parties to that certain Third Amended and Restated Credit Agreement
         dated as of July 14, 1999 (as amended through the date hereof and as
         may be further amended, extended, renewed, or restated from time to
         time, the "Credit Agreement"; terms defined in the Credit Agreement and
         not otherwise defined herein shall be used herein as defined in the
         Credit Agreement).

                  (b) The Borrower has requested an amendment to certain
         financial covenants under the Credit Agreement, and the Administrative
         Agent and the Lenders have agreed to such amendment, subject to the
         terms and conditions contained herein.

         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, the parties
hereto covenant and agree as follows:

         1. AMENDMENTS TO THE CREDIT AGREEMENT. The Credit Agreement is hereby
amended as follows:

                  (a) Section 1.1 is amended by amending and restating in its
         entirety the definition of "Applicable Base Rate Margin" as follows:

                           "Applicable Base Rate Margin" means, with respect to
                  Revolving Credit Advances and Facility A Term Loan Advances,
                  2.00%, per annum, and with respect to Facility B Term Loan
                  Advances, 2.50%, per annum; provided that if the Borrower
                  fails to make the mandatory prepayment required under Section
                  2.5(h) hereof on or before March 8, 2001, the Applicable Base
                  Rate Margin with respect to the Term Loan Advances shall be
                  immediately increased, without notice, by an additional 0.25%.

                  (b) Section 1.1 is amended by amending and restating in its
         entirety the definition of "Applicable LIBOR Rate Margin" as follows:


<PAGE>   2

                           "Applicable LIBOR Rate Margin" means, with respect to
                  Revolving Credit Advances and Facility A Term Loan Advances,
                  3.50%, per annum, and with respect to Facility B Term Loan
                  Advances, 4.00%, per annum; provided that if the Borrower
                  fails to make the mandatory prepayment required under Section
                  2.5(h) hereof on or before March 8, 2001, the Applicable LIBOR
                  Rate Margin with respect to the Term Loan Advances shall be
                  immediately increased, without notice, by an additional 0.25%.

                  (c) Section 1.1 is amended by amending and restating in its
         entirety the definition of "Permitted Assets Sales" as follows:

                           "Permitted Asset Sales" means (a) the sale of
                  inventory in the ordinary course of business, (b) the sale or
                  discount of accounts receivable arising in the ordinary course
                  of business in connection with the compromise or collection
                  thereof, (c) subject to the other terms and provisions hereof,
                  leases or subleases (or assignments of leases or subleases) or
                  licenses or sublicenses (or assignments of licenses or
                  sublicenses) of any assets in the ordinary course of business
                  and (d) the sale or other disposition of Cash Equivalents in
                  the ordinary course of business.

                  (d) Section 1.1 is amended by inserting the following
         definitions in the appropriate alphabetical order, as follows:

                           "Eligible Accounts" shall mean, at any time, all
                  accounts (as such term is defined in the UCC) of the Borrower
                  and its Subsidiaries created in the ordinary course of
                  business, less any and all rebates and discounts, that satisfy
                  the following conditions:

                           (a) The account complies with all applicable laws,
                  rules, and regulations, including, without limitation, usury
                  laws, the Federal Truth in Lending Act, and Regulation Z of
                  the Board of Governors of the Federal Reserve System;

                           (b) The account has not been outstanding for more
                  than ninety (90) days past the original date of invoice;

                           (c) The account was created in connection with (i)
                  the sale of goods in the ordinary course of business and such
                  sale has been consummated and such goods have been shipped, or
                  (ii) the performance of services in the ordinary course of
                  business and such services have been completed and accepted by
                  the account debtor;

                           (d) The account arises from an enforceable contract,
                  the performance of which has been completed;



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<PAGE>   3

                           (e) The account does not arise from the sale of any
                  good that is on a bill-and-hold, guaranteed sale,
                  sale-or-return, sale on approval, consignment, or any other
                  repurchase or return basis;

                           (f) The Borrower or its Subsidiary has good and
                  indefeasible title to the account and the account is not
                  subject to any Lien except Liens in favor of the
                  Administrative Agent;

                           (g) The account does not arise out of a contract with
                  or order from, an account debtor that, by its terms, prohibits
                  or makes void or unenforceable the grant of a security
                  interest to the Administrative Agent in and to such account;

                           (h) The account is not subject to any setoff,
                  counterclaim, defense, dispute, recoupment, or adjustment
                  other than normal discounts for prompt payment;

                           (i) The account debtor is not insolvent or the
                  subject of any bankruptcy or insolvency proceeding and has not
                  made an assignment for the benefit of creditors, suspended
                  normal business operations, dissolved, liquidated, terminated
                  its existence, ceased to pay its debts as they become due, or
                  suffered a receiver or trustee to be appointed for any of its
                  assets or affairs;

                           (j) The account is not evidenced by chattel paper or
                  an instrument, unless all steps necessary to perfect the
                  Administrative Agent's Lien thereon have been taken;

                           (k) No default exists under the account by any party
                  thereto;

                           (l) The account debtor has not returned or refused to
                  retain, or otherwise notified the Borrower or any Subsidiary
                  of any dispute concerning, or claimed nonconformity of, any of
                  the goods from the sale of which the account arose, but only
                  to the extent of the amount represented by the goods returned,
                  refused, disputed or claimed to be non-conforming;

                           (m) The account is not owed by an Affiliate of the
                  Borrower;

                           (n) The account is payable in Dollars by the account
                  debtor;

                           (o) The account shall be ineligible if the account
                  debtor is domiciled in any country other than the United
                  States of America or



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                  Canada, provided that such accounts owing by accounts debtors
                  domiciled in Canada shall not at any time exceed $100,000;

                           (p) The account shall be ineligible if more than five
                  percent (5%) of the aggregate balances then outstanding on
                  accounts owed by such account debtor and its Affiliates to the
                  Borrower and its Subsidiaries are more than ninety (90) days
                  past due from the dates of their original invoices, and to the
                  extent that the accounts owed by an account debtor and its
                  Affiliates to the Borrower and its Subsidiaries exceed seven
                  and one-half percent (7 1/2%) of the aggregate accounts then
                  owing to the Borrower and its Subsidiaries the amount of such
                  excess shall be ineligible; and

                           (q) The account shall be ineligible if the account
                  debtor is the United States of America or any department,
                  agency, or instrumentality thereof, and the Federal Assignment
                  of Claims Act of 1940, as amended, shall not have been
                  complied with.

                  The amount of the Eligible Accounts owed by an account debtor
                  shall be reduced by the amount of all "contra accounts" and
                  other obligations owed by the Borrower and its Subsidiaries to
                  such account debtor.

                           "Eligible Inventory" shall mean, at any time, all
                  inventory of raw materials and finished goods (but excluding
                  work in process) then owned by (and in the possession or under
                  the control of) the Borrower or its Subsidiaries and held for
                  sale or disposition in the ordinary course, in which the
                  Administrative Agent has a perfected, first priority security
                  interest, valued at the lower of actual cost or fair market
                  value. Eligible Inventory shall not include (a) inventory that
                  has been shipped or delivered to a customer on consignment, a
                  sale-or-return basis, or on the basis of any similar
                  understanding, (b) inventory with respect to which a claim
                  exists disputing title to or right to possession of such
                  inventory, and (c) inventory that is not in good condition or
                  does not comply with any applicable law, rule, or regulation
                  or any standard imposed by any governmental authority with
                  respect to its manufacture, use, or sale.

                           "Revolving Credit Borrowing Base" shall mean, at any
                  time, the lesser of (a) $5,000,000, or (b) the sum of (i) 75%
                  of Eligible Accounts (net of gross trade payables less
                  agreed-upon float and the face amount of Letters of Credit
                  which secure trade payables), plus (ii) 55% of Eligible
                  Inventory, each as shown on the most recent Revolving Credit
                  Borrowing Base Report delivered to Administrative Agent under
                  Section 6.9 hereof.



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<PAGE>   5

                           "Revolving Credit Borrowing Base Report" means a
                  report, certified and signed by an Authorized Signatory, in
                  substantially the form of Exhibit E, appropriately completed.

                           "Scheduled Asset Sales" means those asset sales
                  described on Exhibit F hereto.

                           "Third Amendment Effective Date" means November 20,
                  2000.

                  (e) Section 2.1 is amended by entirely amending clause (a)(i)
         thereof as follows:

                           (i) the principal amount of all outstanding Revolving
                  Credit Advances and Reimbursement Obligations exceed the
                  lesser of (A) the Revolving Credit Borrowing Base, or (B) the
                  Revolving Credit Commitment,

                  (f) Section 2.3 is amended by entirely amending clause (a)(ii)
         thereof as follows:

                           (ii) Interest on the Base Rate Advances shall be
                  computed on the basis of a year of 365 or 366 days, as
                  applicable, for the number of days actually elapsed, and shall
                  be payable in arrears on each Monthly Date and on the
                  Revolving Commitment Maturity Date, the Facility A Term Loan
                  Maturity Date or the Facility B Term Loan Maturity Date, as
                  appropriate.

                  (g) Section 2.3 is amended by entirely amending clause (b)(ii)
         thereof as follows:

                           (ii) Subject to Section 11.9 hereof, interest on each
                  LIBOR Advance shall be computed on the basis of a 360-day year
                  for the actual number of days elapsed, and shall be payable in
                  arrears on the applicable Payment Date and on the Revolving
                  Commitment Maturity Date, the Facility A Term Loan Maturity
                  Date and the Facility B Term Loan Maturity Date, as
                  appropriate; provided, however, that if the Interest Period
                  for such Advance exceeds one month, interest shall be due and
                  payable in arrears on each one-month anniversary of the
                  commencement of such Interest Period during such Interest
                  Period.

                  (h) Section 2.4 is amended by entirely amending the first
         sentence thereof as follows:

                  Subject to Section 11.9 hereof, the Borrower agrees to pay to
                  the Administrative Agent, for the ratable account of the
                  Lenders, a commitment fee (the "Revolving Commitment Fee") on
                  the daily average Unused Portion at the rate of 0.500% per
                  annum.



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<PAGE>   6

                  (i) Section 2.5 is amended by deleting the first sentence of
         clause (b)(ii) thereof and replacing it with the following:

                  (ii) At any time when the limitation in Section 2.1(a)(i) is
                  exceeded, whether because the Revolving Credit Commitment has
                  been fully or partially terminated, canceled or reduced or for
                  any other reason, Borrower shall promptly prepay applicable
                  outstanding Revolving Credit Advances in an amount necessary
                  to reduce the sum of outstanding Revolving Credit Advances and
                  Reimbursement Obligations to an amount less than or equal to
                  the lesser of (A) the Revolving Credit Borrowing Base, or (B)
                  the Revolving Credit Commitment. At any time when the
                  limitation in Section 2.1(a)(ii)(A) is exceeded, whether
                  because the Revolving Credit Commitment has been fully or
                  partially terminated, canceled or reduced or for any other
                  reason, Borrower shall promptly prepay applicable outstanding
                  Revolving Credit Advances in an amount necessary to reduce the
                  sum of outstanding Revolving Credit Advances and Reimbursement
                  Obligations to an amount less than or equal to the Revolving
                  Credit Commitment.

                  (j) Section 2.5(c) is amended entirely, as follows:

                  (c) Prepayments from Sales of Assets.

                           (i) Concurrently with the receipt of Net Cash
                  Proceeds in excess of an aggregate amount equal to $500,000
                  from the sale or disposition by the Borrower or any of its
                  Subsidiaries of any assets (including the Capital Stock of any
                  Subsidiary) sold or disposed of (other than Permitted Asset
                  Sales) at any time, the Borrower shall prepay the Term Loan
                  Advances in a principal amount equal to (A) 100% of such Net
                  Cash Proceeds from asset sales other than Scheduled Asset
                  Sales and (B) 80% of such Net Cash Proceeds from Scheduled
                  Asset Sales.

                           (ii) [Intentionally deleted].

                           (iii) [Intentionally deleted].

                           (iv) Any prepayment made under this Section 2.5(c)
                  shall (A) include accrued but unpaid interest to the date of
                  such prepayment on the principal amount prepaid, (B) not be
                  subject to the notice and minimum payment provisions of this
                  Section 2.5; provided, however, the Borrower shall be required
                  to reimburse each Lender for any loss, cost or expense
                  incurred by such Lender in connection with any such prepayment
                  as set forth in Section 2.9 hereof if any prepayment results
                  in a LIBOR Advance being paid on a day other than the last day
                  of an Interest Period for such LIBOR



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<PAGE>   7

                  Advance, and (C) be applied first to Base Rate Advances, if
                  any, and then to LIBOR Advances.

                           (v) (A) [Intentionally deleted].

                               (B) Any prepayment made under this Section 2.5(c)
                  shall be applied (A) to all of the unpaid scheduled
                  installment payments of the Facility A Term Loan Advances, in
                  inverse order of maturity, at all times until Borrower has
                  made prepayments under this Section 2.5(c) equal to
                  $3,750,000, in the aggregate, and (B) at any time after
                  Borrower has made prepayments under this Section 2.5(c) equal
                  to $3,750,000, in the aggregate, to all of the unpaid
                  scheduled installment payments of the Facility A Term Loan
                  Advances and the Facility B Term Loan Advances, in inverse
                  order of maturity, pro rata based upon the respective
                  principal amounts of the Facility A Term Loan Advances and
                  Facility B Term Loan Advances outstanding at the time of such
                  prepayment (provided, however, if at any time that there are
                  no Facility A Term Loan Advances and Facility B Term Loan
                  Advances outstanding, 100% of any such prepayment shall be
                  applied to repay outstanding Revolving Credit Advances but not
                  to permanently reduce the Revolving Credit Commitment).

                  (k) A new Section 2.5(h) is added immediately following
         Section 2.5(g), as follows:

                           (h) Additional Mandatory Prepayment of Term Loan
                  Advances. If the aggregate amount of prepayments made under
                  Section 2.5(c) prior to March 8, 2001, is less than
                  $15,000,000, the Borrower shall, on March 8, 2001, prepay the
                  Term Loan Advances in a principal amount equal to the
                  difference between $15,000,000 and the actual amount prepaid
                  under Section 2.5(c) prior to March 8, 2001. Such prepayment
                  shall be applied to the Term Loan Advances in accordance with
                  Section 2.5(c) as if made with Net Cash Proceeds from asset
                  sales.

                  (l) Section 2.6(b) is entirely amended, as follows:

                           (b) Mandatory Reduction. (i) On the Revolving
                  Commitment Maturity Date, the Revolving Credit Commitment
                  shall automatically reduce to zero.

                                 (ii) The Revolving Credit Commitment shall be
                  permanently reduced by the amount of any prepayment of
                  Revolving Credit Advances pursuant to Sections 2.5(e) and (f)
                  hereof.

                                 (iii) The Revolving Credit Commitment shall be
                  permanently reduced by the amount of $10,000,000 upon the
                  earlier



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<PAGE>   8

                  of (A) March 8, 2001, or (B) the date upon which the Borrower
                  makes a prepayment under Section 2.5(c) which causes the
                  aggregate amount of all prepayments made under Section 2.5(c)
                  to equal or exceed $15,000,000.

                  (m) Section 2.16(a)(i) is entirely amended, as follows:

                           (i) $7,500,000 (the "Letter of Credit Facility") and

                  (n) Section 6.9 is entirely amended, as follows:

                           Section 6.9 Revolving Credit Borrowing Base Reports.
                  (a)Within 15 days after the end of each month, a Revolving
                  Credit Borrowing Base Report as of the end of such month, (b)
                  within 30 days after the end of each month, a Borrowing Base
                  Report as of the end of such month, and (c) on or before the
                  30th day of each month, a Revolving Credit Borrowing Base
                  Report as of the 15th day of the then current month. In
                  addition to the monthly Borrowing Base Report and Revolving
                  Credit Borrowing Base Report required to be delivered
                  hereunder, the Borrower may provide the Lenders with a
                  Borrowing Base Report or Revolving Credit Borrowing Base
                  Report, as the case may be, reflecting information as of any
                  date subsequent to the previously required Borrowing Base
                  Report or Revolving Credit Borrowing Base Report, as the case
                  may be, and the Borrowing Base or Revolving Credit Borrowing
                  Base, as the case may be, reflected in such updated Borrowing
                  Base Report or Revolving Credit Borrowing Base Report, as the
                  case may be, shall be effective until the Borrower delivers
                  another Borrowing Base Report, or Revolving Credit Borrowing
                  Base Report, as the case may be. Each Revolving Credit
                  Borrowing Base Report shall be accompanied by an accounts
                  receivable aging.

                  (o) A new Section 6.11 is hereby added immediately following
         Section 6.10, as follows:

                           Section 6.11 Business Plan and Reports. Within
                  fifteen (15) days after the end of each month, commencing with
                  the month ending November 30, 2000, a detailed report
                  regarding the Borrower's progress with respect to the matters
                  addressed in its comprehensive business plan delivered to
                  Lenders on or before December 15, 2000, pursuant to the terms
                  of the Third Amendment to Credit Agreement dated as of
                  November 20, 2000, such report to be in form and detail
                  acceptable to the Administrative Agent.



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<PAGE>   9

                  (p) Section 7.5 is entirely amended, as follows:

                           Section 7.5 Sale of Assets. The Borrower shall not,
                  and shall not permit any of its Subsidiaries to, sell, lease,
                  abandon, transfer or otherwise dispose of assets in an
                  aggregate amount effective on and after November 20, 2000, in
                  excess of $500,000, except for the following, so long as no
                  Default exists immediately prior to or after the contemplated
                  transaction: (i) Permitted Asset Sales, so long as the
                  consideration received by the Borrower and its Subsidiaries in
                  connection with such transaction is greater than or equal to
                  the fair market value of such assets as determined in good
                  faith by Borrower; (ii) asset sales other than Scheduled Asset
                  Sales consented to in writing by the Determining Lenders, the
                  Net Cash Proceeds of which are subject to Section 2.5(c)
                  hereof; (iii) transfers resulting from any casualty or
                  condemnation of property or assets; (iv) intercompany sales or
                  transfers of assets among Subsidiaries made in the ordinary
                  course of business; and (v) Scheduled Asset Sales.

                  (q) Sections 7.10, 7.11 and 7.12 are each entirely amended, as
         follows:

                           Section 7.10 [Intentionally Omitted]

                           Section 7.11 [Intentionally Omitted]

                           Section 7.12 [Intentionally Omitted]

                  (r) Section 8.1(c) is amended entirely, as follows:

                           (c) The Borrower or any of its Subsidiaries shall
                  default in the performance or observance of any agreement or
                  covenant contained in (i) Section 5.1 or Article 7 hereof,
                  provided that the Borrower's failure to comply with Section
                  7.11 of this Agreement with respect to fiscal quarters ending
                  on or before December 31, 2000, shall only constitute an Event
                  of Default if such noncompliance shall occur in two
                  consecutive fiscal quarters, or (ii) on and after the Third
                  Amendment Effective Date, Sections 6.1, 6.2, 6.3, 6.7, 6.9, or
                  6.11;

                  (s) New Exhibits E and F are added to the Credit Agreement in
         the form of, and all references in the Credit Agreement to Exhibits E
         and F are hereby deemed to be references to, the attached Exhibits E
         and F.

         2. EFFECTIVENESS OF CERTAIN AMENDMENTS. Notwithstanding any other
provision herein to the contrary, the amendments described in Section 1(q) above
shall be effective as of September 30, 2000, and shall terminate automatically
without any action by the Administrative Agent, the Lenders or any other Person
and be of no further force or effect upon the earliest to occur



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of (a) October 1, 2001, or (b) the occurrence of an Event of Default (such
period of effectiveness being referred to herein as the "Covenant Amendment
Period"). The parties hereto acknowledge and agree that upon termination of the
Covenant Amendment Period, the financial covenants amended by Section 1(q)
hereof shall be reinstated in their entirety as if never amended hereby, and an
Event of Default will then exist under the Credit Agreement unless a further
agreement has been entered into among the necessary Persons.

         3. MINIMUM EBITDA COVENANT. During the Covenant Amendment Period, the
Borrower will not permit EBITDA (exclusive of up to $3,595,000 in restructuring
charges incurred in the fourth quarter of fiscal year 2000) for the periods set
forth below to be less than the amount set forth opposite each such period:

<TABLE>
<CAPTION>
               Period                                      Amount
               ------                                      ------
<S>                                                      <C>
       1 month ended 10/31/00                            $(1,000,000)
       2 months ended 11/30/00                           $(2,000,000)
       3 months ended 12/31/00                           $(3,000,000)
       4 months ended 1/31/01                            $(3,500,000)
       5 months ended 2/28/01                            $(3,483,000)
       6 months ended 3/31/01                            $(3,156,000)
       7 months ended 4/30/01                            $(2,567,000)
       8 months ended 5/31/01                            $(2,077,000)
       9 months ended 6/30/01                            $(1,437,000)
       10 months ended 7/31/01                           $(994,000)
       11 months ended 8/31/01                           $(384,000)
       12 months ended 9/30/01                           $256,000
</TABLE>

The required minimum cumulative EBITDA may be adjusted upon terms satisfactory
to Borrower and Determining Lenders from time to time as a result of asset
sales.

         4. MINIMUM TRADE PAYABLES COVENANT. During the Covenant Amendment
Period, the Borrower will not permit outstanding trade payables of the Borrower
and its Subsidiaries for the periods set forth below to be less than the amount
set forth opposite each such period:

<TABLE>
<CAPTION>
               Period                                      Amount
               ------                                      ------
<S>                                                     <C>
       Month ended 10/31/00                             $31,705,000
       Month ended 11/30/00                             $27,935,000
       Month ended 12/31/00                             $27,430,000
       Month ended 1/31/01                               $22,825,000
       Month ended 2/28/01                               $24,860,000
       7 months ended 9/30/01                            $27,490,000
</TABLE>

The required minimum trade payables outstanding may be adjusted upon terms
satisfactory to Borrower and Determining Lenders from time to time as a result
of asset sales.

         5. ADDITIONAL EVENT OF DEFAULT. It will be an Event of Default if the
Borrower shall fail, on or before December 15, 2000, to deliver to Lenders a
comprehensive business



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<PAGE>   11

plan, acceptable as to scope to the Administrative Agent and its counsel and
financial consultants, including, without limitation, separate financial
projections for the divisions of the Borrower and its Subsidiaries.

         6. AMENDMENT FEE. The Borrower shall pay to the Administrative Agent,
for the pro rata account of each Lender, an amendment fee equal to $100,000 (the
"Amendment Fee"). Such Amendment Fee shall be allocated to each Lender pro rata,
based on the sum of (a) such Lender's Revolving Credit Specified Percentage
multiplied by $5,000,000 plus (b) the total outstanding principal amount of all
Term Loan Advances owed to such Lender as of the date of this Amendment. Such
amendment fee shall be earned and payable as of the date of this Amendment in
immediately available funds.

         7. ACKNOWLEDGMENT OF THE BORROWER. The Borrower acknowledges and agrees
that the Lenders executing this Amendment have done so in their sole discretion
and without any obligation.

         8. SUBSIDIARIES ACKNOWLEDGMENT. By signing below, each of the
Subsidiaries which has executed a Subsidiary Guaranty (a) consents and agrees to
the execution and delivery of this Amendment, (b) ratifies and confirms its
obligations under its Subsidiary Guaranty, (c) acknowledges and agrees that its
obligations under its Subsidiary Guaranty are not released, diminished,
impaired, reduced, or otherwise adversely affected by this Amendment, and (d)
acknowledges and agrees that it has no claims or offsets against, or defenses or
counterclaims to, its Subsidiary Guaranty.

         9. RELEASE.

                  (a) The Borrower and each Subsidiary Guarantor hereby
         unconditionally and irrevocably remises, acquits, and fully and forever
         releases and discharges the Administrative Agent and the Lenders and
         all respective affiliates and subsidiaries of the Administrative Agent
         and the Lenders, their respective officers, servants, employees,
         agents, attorneys, principals, directors and shareholders, and their
         respective heirs, legal representatives, successors and assigns
         (collectively, the "Released Lender Parties") from any and all claims,
         demands, causes of action, obligations, remedies, suits, damages and
         liabilities (collectively, the "Borrower Claims") of any nature
         whatsoever, whether now known, suspected or claimed, whether arising
         under common law, in equity or under statute, which the Borrower or any
         Guarantor ever had or now has against the Released Lender Parties which
         may have arisen at any time on or prior to the date of this Amendment
         and which were in any manner related to any of the Loan Documents or
         the enforcement or attempted enforcement by the Administrative Agent or
         the Lenders of rights, remedies or recourses related thereto.

                  (b) The Borrower and each Subsidiary Guarantor covenants and
         agrees never to commence, voluntarily aid in any way, prosecute or
         cause to be commenced or prosecuted against any of the Released Lender
         Parties any action or other proceeding based upon any of the Borrower
         Claims which may have arisen at any time on or prior to the date of
         this Amendment and were in any manner related to any of the Loan
         Documents.



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<PAGE>   12

                  (c) The agreements of the Borrower and each Guarantor set
         forth in this Section 9 shall survive termination of this Amendment and
         the other Loan Documents.

         10. REPRESENTATIONS AND WARRANTIES TRUE, NO EVENT OF DEFAULT. By its
execution and delivery hereof, the Borrower represents and warrants to the
Lenders that, as of the date hereof:

                  (a) after giving effect to this Amendment, the representations
         and warranties contained in the Credit Agreement and the other Loan
         Documents are true and correct in all material respects on and as of
         the date hereof as made on and as of such date, except for any
         representations and warranties made as of a specific date, which shall
         be true and correct in all material respects as of such specific date;
         and

                  (b) after giving effect to this Amendment, no event has
         occurred and is continuing which constitutes a Default or an Event of
         Default.

         11. CONDITIONS OF EFFECTIVENESS. This Amendment shall not be effective
until each of the following conditions precedent shall have been satisfied:

                  (a) All reasonable out-of-pocket fees and expenses in
         connection with the Loan Documents, including this Amendment, including
         legal and other professional fees and expenses incurred on or prior to
         the date of this Amendment by the Administrative Agent, including,
         without limitation, the fees and expenses of Winstead Sechrest & Minick
         P.C. and Arthur Andersen L.L.P., shall have been paid; and

                  (b) The Administrative Agent shall have received such
         documents, certificates and instruments as the Administrative Agent
         shall reasonably require; and

                  (c) The Administrative Agent shall have received for the
         account of the Lenders the Amendment Fee described in Section 6 of this
         Amendment.

         12. REFERENCE TO CREDIT AGREEMENT. Upon the effectiveness of this
Amendment, each reference in the Credit Agreement to "this Agreement,"
"hereunder," or words of like import shall mean and be a reference to the Credit
Agreement, as affected and amended by this Amendment.

         13. COUNTERPARTS; EXECUTION VIA FACSIMILE. This Amendment may be
executed in one or more counterparts, each of which shall be deemed an original,
but all of which together shall constitute one and the same instrument. This
Amendment may be validly executed and delivered by facsimile or other electronic
transmission.

         14. GOVERNING LAW: BINDING EFFECT. This Amendment shall be governed by
and construed in accordance with the laws of the State of Texas and shall be
binding upon the Borrower, the Administrative Agent, each Lender and their
respective successors and assigns.



                                       12
<PAGE>   13

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

         16. LOAN DOCUMENT. This Amendment is a Loan Document and is subject to
all provisions of the Credit Agreement applicable to Loan Documents, all of
which are incorporated in this Amendment by reference the same as if set forth
in this Amendment verbatim.

         17. NO ORAL AGREEMENTS. THIS WRITTEN AGREEMENT AND THE OTHER LOAN
DOCUMENTS REPRESENT THE FINAL AGREEMENT BETWEEN THE PARTIES AND MAY NOT BE
CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT ORAL
AGREEMENTS OF THE PARTIES. THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN THE
PARTIES.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]



                                       13
<PAGE>   14

         IN WITNESS WHEREOF, the parties hereto have executed this Amendment as
the date first above written.



                                             KEVCO, INC.

                                             By:
                                                --------------------------------
                                                    Joseph P. Tomczak
                                                    Executive Vice President and
                                                    Chief Financial Officer

                                             BANK OF AMERICA, N.A., formerly
                                             known as NationsBank, N.A., as
                                             Administrative Agent and as a
                                             Lender

                                             By:
                                                --------------------------------
                                                    Mike V. Colon
                                                    Vice President



                                             NATIONAL CITY BANK OF KENTUCKY

                                             By:
                                                --------------------------------
                                                Name:
                                                     ---------------------------
                                                Title:
                                                      --------------------------



                                             GUARANTY FEDERAL BANK, F.S.B.

                                             By:
                                                --------------------------------
                                                Name:
                                                     ---------------------------
                                                Title:
                                                      --------------------------
<PAGE>   15


                                             WELLS FARGO BANK, N.A.

                                             By:
                                                --------------------------------
                                                Name:
                                                     ---------------------------
                                                Title:
                                                      --------------------------



                                             PILGRIM PRIME RATE TRUST

                                             By: Pilgrim Investments, Inc., as
                                                 its Investment Manager

                                             By:
                                                --------------------------------
                                                Name:
                                                     ---------------------------
                                                Title:
                                                      --------------------------



                                             ARCHIMEDES FUNDING, L.L.C.

                                             By: ING Capital Advisors, Inc., as
                                                 Collateral Manager

                                             By:
                                                --------------------------------
                                                Name:
                                                     ---------------------------
                                                Title:
                                                      --------------------------



                                             ALLIANCE CAPITAL FUNDING, L.L.C.

                                             By: Alliance Capital Management,
                                                 L.P., as Manager on behalf of
                                                 ALLIANCE CAPITAL FUNDING,
                                                 L.L.C.

                                                 By: ALLIANCE CAPITAL MANAGEMENT
                                                     CORPORATION
                                                     General Partner of Alliance
                                                     Capital Management, L.P.

                                                 By:
                                                    ----------------------------
                                                 Name:
                                                      --------------------------
                                                 Title:
                                                       -------------------------

<PAGE>   16


                               BANK ONE, TEXAS, N.A.

                               By:
                                  --------------------------------------
                                   Name:
                                        --------------------------------
                                   Title:
                                         -------------------------------



                               PAM CAPITAL FUNDING LP

                               By: Highland Capital Management, L.P.,
                                   as Collateral Manager

                               By:
                                  --------------------------------------
                                   Name:
                                        --------------------------------
                                   Title:
                                         -------------------------------



                               ML CBO IV (CAYMAN) LTD.

                               By: Highland Capital Management, L.P., as
                                   Collateral Manager

                               By:
                                  --------------------------------------
                                   Name:
                                        --------------------------------
                                   Title:
                                         -------------------------------


ACKNOWLEDGED AND AGREED:

KEVCO MANAGEMENT, INC.

By:
   --------------------------------------
    Name:
         --------------------------------
    Title:
          -------------------------------
<PAGE>   17

KEVCO HOLDING, INC.

By:
   --------------------------------------
    Name:
         --------------------------------
    Title:
          -------------------------------



KEVCO GP, INC.

By:
   --------------------------------------
    Name:
         --------------------------------
    Title:
          -------------------------------



KEVCO COMPONENTS, INC.

By:
   --------------------------------------
    Name:
         --------------------------------
    Title:
          -------------------------------



DCM DELAWARE, INC.

By:
   --------------------------------------
    Name:
         --------------------------------
    Title:
          -------------------------------



KEVCO MANUFACTURING, L.P.

By: KEVCO GP, INC., its General Partner

By:
   --------------------------------------
    Name:
         --------------------------------
    Title:
          -------------------------------


<PAGE>   18

KEVCO DISTRIBUTION, L.P.

By: KEVCO GP, INC., its General Partner

By:
   --------------------------------------
    Name:
         --------------------------------
    Title:
          -------------------------------


<PAGE>   19
                                    EXHIBIT E

                     REVOLVING CREDIT BORROWING BASE REPORT

ADMINISTRATIVE AGENT: Bank of America, N.A.                   DATE:
                                                                   -------------
BORROWER: Kevco, Inc.

     This Revolving Credit Borrowing Base Report, prepared as of , is executed
and delivered by Borrower pursuant to that certain Third Amended and Restated
Credit Agreement dated as of July 14, 1999 among the Borrower, each of the banks
or other lending institutions which is or may from time to time become a
signatory thereto and any successors or permitted assigns thereof ("Lenders")
and Administrative Agent (as amended, supplemented or modified from time to
time, the "Credit Agreement"). All terms used herein shall have the meanings
assigned to them in the Credit Agreement.

     Borrower represents and warrants to Administrative Agent that all
information contained herein is true, correct, and complete, and that the total
Eligible Accounts and total Eligible Inventory referred to below represent the
Eligible Accounts and Eligible Inventory that qualify for purposes of
determining the Revolving Credit Borrowing Base under the Credit Agreement.

ELIGIBLE ACCOUNTS:

1.   Accounts (less any and all rebates and discounts)
     (ending balance for period ended __________, 20__) ........$ ______________

2.   Less: Ineligible Accounts (determined pursuant to the
     definition of Eligible Accounts in the Credit
     Agreement), including, without duplication:

     (a)  Accounts not paid within 90 days of original
          invoice date .........................................$ ______________

     (b)  Accounts subject to any setoff, counterclaim,
          defense, dispute, recoupment, or adjustment other
          than normal discounts for prompt payment .............$ ______________

     (c)  Accounts on which the account debtor is not
          domiciled in the United States or Canada .............$ ______________

     (d)  Total accounts on which the account debtor is
          domiciled in Canada less $100,000 (leave blank if
          less than zero) ......................................$ ______________

     (e)  Accounts not arising out of (i) the sale of goods
          in the ordinary course of business which has been
          consummated and such goods have been shipped, or
          (ii) the performance of services in the ordinary
          course of business which have been completed and
          accepted by the account debtor .......................$ ______________

     (f)  Accounts from the sale of any good that is on a
          bill-and-hold, guaranteed sale, sale-or-return,
          sale on approval, consignment, or any other
          repurchase or return basis. ..........................$ ______________

     (g)  Accounts owed by each account debtor with over 5%
          of the balances owed by such account debtor and
          its Affiliates outstanding and payable for more
          than 90 days past the original invoice date ..........$ ______________

     (h)  Accounts not payable in Dollars ......................$ ______________

     (i)  Accounts owed by the United States or any other
          government for which the Federal Assignment of
          Claims Act of 1940, as amended, or other
          applicable law (other than the Uniform Commercial
          Code) has not been complied with .....................$ ______________

     (j)  Accounts owed by account debtor that is insolvent,
          or is the subject any bankruptcy or insolvency
          proceeding or has made an assignment for the
          benefit of creditors, suspended normal business
          operations, dissolved, liquidated, terminated its
          existence, ceased to pay its debts as they become
          due, or suffered a receiver or trustee to be
          appointed for any of its assets or affairs ...........$ ______________

     (k)  Accounts that do not comply with all applicable
          laws, rules, and regulations, including, without
          limitation, usury laws, the Federal Truth in
          Lending Act, and Regulation Z of the Board of
          Governors of the Federal Reserve System. .............$ ______________

     (l)  Accounts not arising from an enforceable contract,
          the performance of which has been completed ..........$ ______________

     (m)  Accounts evidenced by instruments or chattel paper
          with respect to which all steps necessary to
          perfect the Administrative Agent's Lien thereon
          have not been taken ..................................$ ______________

     (n)  Accounts with respect to which a default exists ......$ ______________

     (o)  Accounts with respect to which the account debtor
          has returned or refused to retain, or otherwise
          notified the Borrower or the applicable Subsidiary
          of any dispute concerning, or claimed
          nonconformity of, any of the goods from the sale
          of which the account arose, but only to the extent
          of the amount represented by the goods returned,
          refused, disputed or claimed to be non-conforming ....$ ______________
<PAGE>   20

     (p)  Accounts arising out of a contract with or order
          from, an account debtor that, by its terms,
          prohibits or makes void or unenforceable the grant
          of a security interest to the Administrative Agent
          in and to such account ...............................$ ______________

     (q)  Accounts to which the Borrower or the applicable
          Subsidiary does not have good and indefeasible
          title or which is subject to any Lien except Liens
          in favor of the Administrative Agent .................$ ______________

     (r)  Accounts owed by an Affiliate of the Borrower ........$ ______________

     (s)  With respect to any account debtor, the amount by
          which the amount of all accounts owed by such
          account debtor and its Affiliates to Borrower or
          any of its Subsidiaries exceeds 7-1/2% of the
          aggregate amount of all accounts owed to Borrower
          or any of its Subsidiaries ...........................$ ______________

     (t)  "Contra accounts" and other obligations owed by
          the Borrower and its Subsidiaries to account
          debtors ..............................................$ ______________

3.   Gross trade payables ......................................$ ______________

4.   Agreed-upon float .........................................$ ______________

5.   Face amount of Letters of Credit which secure trade
     payables ..................................................$ ______________

6.   Line 3 minus Line 4 minus Line 5 ..........................$ ______________

7.   Total Ineligible Accounts (sum of Lines 2(a)-(t) plus
     Line 6) ...................................................$ ______________

8.   Total Eligible Accounts (Line 1 minus Line 7) .............$ ______________

ELIGIBLE INVENTORY:

9.   Total Inventory (valued at lesser of actual cost or
     fair market value) ........................................$ ______________

10.  Less: Ineligible Inventory (determined pursuant to the
     definition of Eligible Inventory in the Credit
     Agreement, without duplication)

     (a)  Inventory not with respect to which a claim exists
          disputing title to or right to possession of such
          inventory ............................................$ ______________

     (b)  Work-in-process inventory ............................$ ______________

     (c)  Inventory shipped or delivered on consignment,
          sale or return, or similar terms .....................$ ______________

     (d)  Inventory that is not in good condition or does
          not comply with any applicable law, rule, or
          regulation or any standard imposed by any
          governmental authority with respect to its
          manufacture, use, or sale ............................$ ______________

     (e)  Inventory that is not owned by and in the
          possession or under the control of Borrower or one
          of its Subsidiaries and held for sale or
          disposition in the ordinary course ...................$ ______________

     (f)  Inventory in which the Administrative Agent does
          not have a perfected, first priority security
          interest .............................................$ ______________

11.  Total Ineligible Inventory (sum of Lines 10(a)-(f)) .......$ ______________

12.  Total Eligible Inventory (Line 9 minus Line 11) ...........$ ______________

BORROWING BASE:

13.  Total Eligible Accounts (Line 8) ..........................$ ______________

14.  Total Eligible Inventory (Line 12) ........................$ ______________

15.  75% of Line 13 ............................................$ ______________

16.  55% of Line 14 ............................................$ ______________

17.  Borrowing Base: Sum of Line 15 plus Line 16 ...............$ ______________

18.  Outstanding Revolving Loans ...............................$ ______________

19.  Available Credit Amount or amount to be paid if
     negative [(the lesser of $17,500,000 or Line 17) minus
     Line 18] ..................................................$ ______________

     Borrower further represents and warrants to Administrative Agent and
Lenders that the representations and warranties contained in Article 4 of the
Credit Agreement are true and correct on and as of the date of this Revolving
Credit Borrowing Base Report as if made on and as of the date hereof, and that
no Material Adverse Effect, Default, or Event of Default exists.

Date:                                         KEVCO, INC.
     -------------------
                                              By:
                                                 -------------------------------
                                                 Name:
                                                      --------------------------
                                                 Title:
                                                       -------------------------


<PAGE>   21
                      THIRD AMENDMENT TO CREDIT AGREEMENT
                                   EXHIBIT F
                             SCHEDULED ASSET SALES


<TABLE>
<CAPTION>
                                                                                APPRAISED
                                                              SQUARE              VALUE
      DIVISION                      LOCATION                   FEET           (in thousands)
----------------------    ------------------------------   -------------   ---------------------
<S>                       <C>                              <C>             <C>
Distribution              Bear Creek, Ala.                       90,000                  $  819

Distribution              Douglas, Ga.                           72,000                     750

Distribution              Elkhart, In.
                            27217 CR6 W                          54,500                     660
                            27200 D.I. Drive                     25,200                     500
                            27256 D.I. Drive                     15,000                     300
                            21861 Protecta Drive                 64,000                   1,010
                            2200 Industrial Parkway              84,000                   1,450

Wood                      Spruce Pine, Ala.                      26,400                     170
                                                                -------                  ------

    Totals                                                      431,100                  $5,659
</TABLE>