<PAGE>   1
                                                                  EXHIBIT 10(JJ)

                       FOURTH AMENDMENT TO LOAN AGREEMENT
                            AND OTHER LOAN DOCUMENTS

         THIS FOURTH AMENDMENT TO LOAN AGREEMENT AND OTHER LOAN DOCUMENTS
(this "Amendment") dated as of January 1, 2000 (the "Effective Date"), is
entered into by MARTIN INDUSTRIES, INC., a Delaware corporation which is the
successor by merger to Martin Industries, Inc., an Alabama corporation (the
"Borrower"), and AMSOUTH BANK, an Alabama banking corporation formerly doing
business as AmSouth Bank, N.A., a national banking association, and AmSouth Bank
of Alabama, an Alabama banking corporation (the "Lender").

                                    RECITALS

         A. The Borrower and the Lender are parties to a certain Loan Agreement
dated as of January 7, 1993, as amended by letter of April 5, 1994, and as
assumed and modified by an Assumption and Modification Agreement dated February
17, 1995, and as further modified and amended by a First Amendment to Loan
Agreement and other Loan Documents dated as of March 15, 1995, and as further
modified and amended by a Second Amendment to Loan Agreement and Other Documents
dated as of March 28, 1996, and as further modified and amended by a Third
Amendment to Loan Agreement and Other Loan Documents dated as of August 28, 1997
(the "Loan Agreement").

         B. The Borrower and the Lender wish further to amend the Loan Agreement
to make the changes set forth in this Amendment.

         C. The Borrower and Lender are parties to a certain General Security
Agreement dated as of January 7, 1993 (the "Security Agreement").

         D. The Borrower and the Lender wish to amend the Security Agreement to
make the changes set forth in this Amendment.


                                    AGREEMENT

         NOW, THEREFORE, in consideration of the foregoing recitals and in
further consideration of the mutual agreements set forth herein, effective as of
the Effective Date, the Borrower and the Lender hereby agree as follows:

         1. DEFINITIONS. Capitalized terms used in this Agreement and not
otherwise defined herein have the meanings defined for them in the Loan
Agreement.



                                       -1-

<PAGE>   2



         2. REPRESENTATIONS AND WARRANTIES OF BORROWER. The Borrower represents
and warrants to the Lender that as of the Effective Date no Event of Default
(nor any event that upon notice or lapse of time or both would constitute an
Event of Default) exists under the Loan Agreement or any of the other Loan
Documents.

         3. AMENDMENTS TO LOAN AGREEMENT AS OF EFFECTIVE DATE. Effective as of
the Effective Date, the Loan Agreement is amended as follows:

                  (A) The following new definitions are added in alphabetical
         order in Section 1.02:

                           ACCOUNTS shall have the meaning assigned to that term
                           in the Security Agreement.

                           BORROWING BASE shall mean the sum of (a) 20% of the
                           collateral value of Eligible Inventory, plus (b) 80%
                           of the Net Outstanding Amount of Eligible Accounts.

                           ELIGIBLE ACCOUNT shall mean and include only Accounts
                           that are not more than 30 days past due, in each case
                           according to the terms shown on the invoice (or the
                           date of the invoice where terms are not specifically
                           stated) and represent sums payable for services
                           rendered or goods sold or leased by the Borrower in
                           the ordinary course of business, as the Lender, in
                           its sole credit judgment, shall deem eligible based
                           on such credit and collateral considerations as the
                           Lender shall deem appropriate. Without limiting the
                           generality of the foregoing, the Lender may exclude
                           any Account from Eligible Accounts if:

                                    (i) the subject goods have been shipped or
                           delivered to a Purchaser on a bill-and-hold,
                           guaranteed sale, consignment, approval or sale-or-
                           return basis or subject to any other repurchase or
                           return agreement; or

                                    (ii)    any material part of the subject
                           goods has been returned, rejected, lost or damaged;
                           or

                                    (iii) the Purchaser is located outside the
                           United States and Canada, and the subject goods have
                           not been shipped on the security of a domestic
                           banker's acceptance or domestic letter of credit
                           acceptable to the Lender and pledged to the Lender,
                           or the Account is not payable in United States
                           dollars; or



                                       -2-

<PAGE>   3
                                    (iv)  the Purchaser is also the Borrower's
                           Affiliate, supplier or creditor; or

                                    (v) the Account is not evidenced by an
                            invoice in form acceptable to the Lender; or

                                    (vi) more than 25% in amount of the other
                           Accounts of the Purchaser are more than 90 days past
                           due; or

                                    (vii) such Account is from a Purchaser
                           located in Canada and after taking such Account into
                           consideration, such Canadian Accounts in the
                           aggregate would constitute more than 20% of the
                           outstanding Accounts; or

                                    (viii) the Account arises out of
                            transactions with an employee, officer, agent,
                            director, stockholder or Affiliate of the Borrower;
                            or

                                    (ix) the general creditworthiness and
                            financial condition of the Purchaser are not
                            acceptable to the Lender; or

                                    (x) the Lender believes, in its sole
                           judgment, that the collection of such Account is
                           insecure or that such Account may not be paid by
                           reason of the Purchaser's financial ability to repay;
                           or

                                    (xi) the Borrower has disclosed to the
                           Lender that it does not make any of the
                           representations or warranties set forth in the
                           Security Agreement with respect to such Account or if
                           any of such representations or warranties are not
                           true and correct with respect to such Account.

                           ELIGIBLE INVENTORY shall mean and include only
                           Inventory of raw materials, finished goods and
                           purchased parts that is located at one of the
                           locations specified in the Security Agreement as the
                           places at which Inventory is to be maintained, that
                           is usable or saleable in the ordinary course of the
                           Borrower's business and that meets all standards
                           imposed by any Governmental Authority having
                           regulatory authority over such goods or over their
                           use or sale, as the Lender, in its sole judgment,
                           shall deem eligible, based on such credit and
                           collateral considerations as the Lender shall deem
                           appropriate. Without limiting the generality of the
                           foregoing, the Lender may exclude any Inventory from
                           Eligible Inventory if the Borrower has disclosed to
                           the Lender that it does not make any of the
                           representations or warranties set forth in the
                           Security Agreement with respect to such Inventory or
                           any of such representations and warranties are not
                           true and correct with respect to such Inventory. The
                           collateral value of


                                       -3-

<PAGE>   4
                           Eligible Inventory shall be computed at the lower of
                           cost or market and on a "first-in, first-out" (FIFO)
                           basis.

                           FOURTH AMENDMENT shall mean the Fourth Amendment to
                           Loan Agreement and Other Loan Documents between the
                           Borrower and the Lender as of _____________, ____,
                           which document amends certain of the provisions of
                           this Agreement.

                           INVENTORY shall have the meaning assigned to that
                           term in the Security Agreement.

                           NET OUTSTANDING AMOUNT OF ELIGIBLE ACCOUNTS shall
                           mean the net outstanding amount of all then Eligible
                           Accounts after eliminating from the aggregate face
                           amount thereof all payments, adjustments, discounts,
                           credits and allowances applicable thereto and all
                           amounts due thereon considered by the Lender
                           difficult to collect or uncollectible by reason of
                           return, rejection, repossession or loss of, or damage
                           to, the merchandise covered thereby, disputes,
                           financial difficulty of the Purchaser or otherwise,
                           all as determined by the Lender in its sole
                           discretion.

                           TANGIBLE NET WORTH shall mean Borrower's consolidated
                           net worth plus subordinated debt less (i) any and all
                           loans and other advances to affiliates, subsidiaries,
                           owners, parent, employees, officers, stockholders,
                           directors or other related entities of Borrower; (ii)
                           notes, notes receivable, accounts, accounts
                           receivable, inter-company receivables, and other
                           amounts owing from affiliates, subsidiaries, owners,
                           parent, employees, officers, stockholders, directors
                           or other related entities of Borrower; and (iii) any
                           and all intangibles of Borrower.

                  (B)      The following definitions are amended as follows:

                           MAXIMUM LINE OF CREDIT shall mean the lesser of (i)
                           the Borrowing Base then in effect or (ii)
                           $10,000,000.

                           LIBOR-BASED RATE shall mean a fixed rate of one
                           hundred twenty-five (125) basis points in excess of
                           the average offered rate in the London interbank
                           market for deposits in U.S. dollars for thirty (30)
                           days (the "LIBOR Rate") as published in the Wall
                           Street Journal or such other comparable financial
                           information reporting service used by the Bank at the
                           time such rate is determined.

                           SECURITY AGREEMENT shall mean that certain General
                           Security Agreement dated January 7, 1993 and that
                           certain Security Agreement of even date


                                       -4-

<PAGE>   5

                           herewith executed by the Borrower in favor of the
                           Lender to secure the Liabilities, as each may be
                           amended from time to time.




                  (C) The date "May 31, 1993" in the definition of "Line of
         Credit Termination Date" in Section 1.02, which was previously extended
         to July 31, 1999, is further amended to read "January 1, 2001."

                  (D) The figure $15,000,000" that appears in the fourth line of
         Section 3.02, which was previously amended to $30,000,000", is further
         amended to read "$10,000,000".

                  (E) Section 3.06 is amended to change the rate of the
         Availability Fee in the third line from "fourteen (14)" to "twenty
         (20)" basis points.

                  (F) The following new Section 7.17, previously deleted, shall
         be added:

                           SECTION 7.17. ANNUAL SIXTY-DAY LINE OF CREDIT
                           CLEAN-UP PERIOD. The Borrower will for a period of at
                           least sixty (60) consecutive days during each
                           calendar year cause the outstanding advances under
                           the Line of Credit to be paid in full and shall
                           maintain the principal balance of the Line of Credit
                           at zero.

                  (G) Section 8.02 shall be amended to read as follows:

                           SECTION 8.02. DEBT. The Borrower will not incur,
create, assume or permit to exist any Debt other than (a) Debt to the Lender,
(b) trade payables and other current liabilities incurred or accrued by the
Borrower in the ordinary course of business, (c) the extension or receipt of
normal trade terms with respect to customers and suppliers, (d) any specific
Debt in connection with a special transaction for which advance approval is
sought and obtained from the Lender, (e) leases of equipment incurred in the
ordinary course of the Borrower's business, (f) unsecured Debt incurred in the
ordinary course of the Borrower's business not exceeding $125,000 in aggregate
principal amount at any one time outstanding, (g) Debt that is subordinated, in
writing, to Borrower's Debt to the Lender, and (h) Debt incurred solely for the
purchase of assets held or acquired by the Borrower in the ordinary course of
business.

                  (H) Section 8.03 shall be amended to read as follows:

                           SECTION 8.03. LIENS. The Borrower will not incur,
create, assume or suffer to exist any Lien on any of its properties or
assets, now or hereafter owned, other than:

                           (a) deposits under workmen's compensation,
         unemployment insurance and Social Security laws, or to secure the
         performance of bids, tenders, contracts (other than for the repayment
         of borrowed money) or leases or to secure statutory obligations or
         surety

                                       -5-

<PAGE>   6


         or appeal bonds, or to secure indemnity, performance or other similar
         bonds in the ordinary course of business;


                           (b) Liens imposed by law, such as carriers',
         warehousemen's or mechanics' liens, incurred in good faith in the
         ordinary course of business, and any lien arising out of a judgment or
         award not exceeding $150,000 with respect to which an appeal is being
         prosecuted, a stay of execution pending such appeal having been
         secured, or which is fully covered by valid and collectible insurance;

                           (c)  Permitted Encumbrances;

                           (d)  Liens not listed above that are the subject of
         Permitted Contests; and

                           (e) purchase money liens or purchase money security
         interests upon or in any property acquired or held by the Borrower in
         the ordinary course of its business.

                  (I) Section 8.04 shall be amended to read as follows:

                           SECTION 8.04. GUARANTIES. (a) The Borrower will not
guarantee, endorse, become surety for, or otherwise in any way become or be
responsible for obligations of any other Person, whether by agreement to
purchase the indebtedness of any other Person, or agreement for the furnishing
of funds to any other Person (directly or indirectly, through the purchase of
goods, supplies or services or by way of stock purchase, capital contribution,
working capital maintenance agreement, advance or loan) or for the purpose of
paying or discharging the indebtedness of any other Person, or otherwise, or (b)
enter into or be a party to any contract for the purchase of merchandise,
materials, supplies or other property if such contract provides that payment for
such merchandise, materials, supplies or other property shall be made regardless
of whether delivery of such merchandise, materials, supplies or other property
is ever made or tendered; except for the endorsement of negotiable instruments
by the Borrower in the ordinary course of business for collection.

                  (J) Section 8.05 shall be amended to read as follows:

                           SECTION 8.05. SALE OF ASSETS, CONSOLIDATION, MERGER,
ETC. Without the prior written consent of Lender, the Borrower will not (a)
sell, lease, transfer or otherwise dispose of its properties and/or assets to
any Person, (b) consolidate with or merge into any corporation, or permit
another corporation to merge into it, or acquire all or substantially all the
properties or assets of any other Person, or (c) enter into any arrangement,
directly or indirectly, with any Person whereby the Borrower shall sell or
transfer any property, real, personal or mixed, and used and useful in its
business, whether now owned or hereafter acquired, and thereafter rent or lease
such property or other property that the Borrower intends to use for
substantially the same purpose or purposes as the property being sold or
transferred.


                                       -6-

<PAGE>   7

                  (K) Section 8.06 shall be amended to read as follows:





                           SECTION 8.06. INVESTMENTS, ETC. The Borrower will not
purchase or hold beneficially any stock, other securities or evidences of
indebtedness of, make or permit to exist any loans or advances to, or make any
investment or acquire any interest whatsoever in, any other Person, except that
the Borrower may invest in Permitted Investments, so long as at all times the
instruments evidencing all such Permitted Investments are in the possession of
the Lender or the Lender's security interest therein under the Security
Agreement is otherwise effectively perfected. Notwithstanding anything to the
contrary contained in this Section, the Borrower may (a) extend normal trade
terms to customers in the ordinary course of its business, and (b) make loans to
employees not exceeding $50,000 in principal amount for all such loans
outstanding at any one time, in the aggregate.

                  (L) Section 8.09 shall be amended to read as follows:

                           SECTION 8.09 DEBT SERVICE COVERAGE RATIO. The
Borrower will not permit its ratio of Net Cash Flow Before Interest Expense to
Debt Service to be less than:

                           (i)      as of December 31, 2000 - 1.25 to 1; and
                           (ii)     as of December 31, 2001 and each year
                                    thereafter - 1.5 to 1.

                  (M) Section 8.11 is amended by deleting the figure "1.5" and
         substituting therefor the figure "2.0".

                  (N) Section 8.12 is amended by deleting the figure "1.0" and
         substituting therefor the figure "1.25".

                  (O) Section 8.13 shall be amended to read as follows:

                           SECTION 8.13. TANGIBLE NET WORTH. The Borrower will
not permit its Tangible Net Worth to be less than $37,000,000.00.

                  (P) Section 8.15 shall be amended to read as follows:

                           SECTION 8.15. CAPITAL EXPENDITURES. The Borrower will
not make Capital Expenditures in an aggregate amount exceeding $5,000,000 in
any fiscal year.

                  (Q) The following new Section 8.17 is added:

                           SECTION 8.17. COMPLIANCE WITH LAWS AND REGULATIONS.
The Borrower shall comply in all material respects with all applicable laws,
ordinances and regulations relating to its business operations.



                                      -7-

<PAGE>   8


                  (R)      The following new Section 8.19 is added:



                           SECTION 8.19. ADVANCES. Borrower shall not extend any
                           loans or advances to any other Person, except as
                           authorized by Section 8.02.

                  (S)      subparagraphs (c) and (k) of IX. EVENTS OF DEFAULT;
                           ACCELERATION shall be amended to read as follows:

                           (c) default shall be made in the payment of the
                           principal of or interest on any of the Liabilities,
                           as and when due and payable; or

                           (k) any default or event of default shall occur
                           under any of the other Loan Documents;

         4. MODIFIED LINE OF CREDIT NOTE. To evidence certain of the changes
effected by this Amendment, the Borrower shall execute and deliver to the Lender
a Modified, Amended and Restated Line of Credit Note substantially in the form
attached hereto as Exhibit A (the "Modified Line of Credit Note"). Commencing on
the Effective Date the Modified, Amended and Restated Line of Credit Note shall
be the "Line of Credit Note" referred to in the Loan Agreement and other Loan
Documents. The Lender may retain the original Line of Credit Note dated January
7, 1993, the Modified, Amended and Restated Line of Credit Note dated March 15,
1995, and the Modified, Amended and Restated Line of Credit Note dated August
28, 1997, in its file along with the Modified, Amended and Restated Line of
Credit Note of even date until the indebtedness evidenced thereby has been paid
in full and the Line of Credit has been terminated as set forth in the Loan
Agreement.

         5. AMENDMENTS TO SECURITY AGREEMENT AS OF EFFECTIVE DATE.
Effective as of the Effective Date, the Security Agreement is amended as
follows:

         Subparagraph (e) of Article 6, Events of Default, is deleted in its
entirety.

         6. REFERENCES IN LOAN DOCUMENTS. Effective as of the Effective Date,
all references in the Loan Documents to the "Loan Agreement" shall mean the Loan
Agreement, as heretofore modified and amended and as further modified and
amended by this Amendment, all references to the "Line of Credit Note" shall
mean the Modified, Amended and Restated Line of Credit Note of even date
referred to in this Amendment and all references in the Loan Documents to the
"Security Agreement" shall mean the Security Agreement as modified and amended
by the Amendment. Effective as of the Effective Date, the words "fifteen million
dollars" and figure "15,000,000" as used in any of the Loan Documents to refer
to the maximum principal amount of the Line of Credit Master Note, amended to
"ten million dollars" and $10,000,000", as further amended to read "thirty
million dollars" and $30,000,000" are further amended to read "ten million
dollars" and "$10,000,000", respectively.


                                       -8-

<PAGE>   9


         7. ADDITIONAL SECURITY AGREEMENT. As additional security for the Notes,
Borrower shall execute an additional security agreement of even date granting to
Lender a security interest in the Accounts and Inventory of the Borrower as an
additional Security Document as defined in the Loan Agreement.

         8. LOAN DOCUMENTS TO REMAIN IN EFFECT. Except as specifically modified
by this Amendment, the Loan Agreement and the other Loan Documents are
incorporated herein by reference as if fully set out and shall remain and/or be
reaffirmed in full force and effect in accordance with their respective terms.

         9. FINANCIAL MONITORING. Unless an Event of Default has occurred,
notwithstanding anything to the contrary herein or in the Agreement, Borrower
shall provide Lender the following financial information:

                  (a) The Financial Statements and Reports required under the
         Agreement in Section 7.04 (a), (b), (d) and (e) and such other
         information as Lender may reasonably request to verify the Borrowing
         Base; and

                  (b) At the Lender's request, the Borrower will submit
         monthly or weekly borrowing base certification.

         10. NO NOVATION, ETC. Nothing contained in this Amendment shall be
deemed to constitute a novation of the terms of the Loan Documents, or impair
any Liens granted to the Lender thereunder, or affect any of the rights, powers
or remedies of the Lender thereunder or constitute a waiver of any provision
thereof, except as specifically set forth in this Amendment.

         11. GOVERNING LAW, SUCCESSORS AND ASSIGNS, ETC. This Amendment shall be
governed by and construed in accordance with the laws of the State of Alabama
and shall be binding upon and inure to the benefit of the parties hereto and
their respective successors and permitted assigns.

         12. DATE. The date of this Amendment is intended as and for a date for
the convenient identification of this Amendment and for determining the
Effective Date hereof, and is not intended to indicate that this Amendment was
executed and delivered on said date.

         13. SEVERABILITY. If any provision of this Amendment shall be invalid,
illegal or unenforceable, the validity, legality and enforceability of the
remaining provisions shall not in any way be affected or impaired thereby.

         14. COUNTERPARTS. This Amendment may be executed in any number of
counterparts, each of which so executed shall be deemed an original, but all
counterparts shall together constitute but one and the same instrument.


                                       -9-

<PAGE>   10


         15. NO WAIVER. Nothing contained herein shall be construed as a waiver,
acknowledgment or consent to any breach of or Event of Default under the
Agreement and the Loan Documents not specifically mentioned herein, and the
consents granted herein are effective only in the specific instance and for
the purposes for which given.

         16. $5,000,000 TERM LOAN. On or about the date of execution, the
$5,000,000 Term Loan shall be paid in full and all or part of said payment shall
be made with proceeds from the Line of Credit.

         IN WITNESS WHEREOF, the Borrower and the Lender have caused this
Amendment to be executed and delivered by their duly authorized representatives,
effective as of the date first set forth above.

                                     MARTIN INDUSTRIES, INC.,
                                     a Delaware corporation



                                     By:            /S/   RODERICK V. SCHLOSSER
                                         ---------------------------------------
                                         Its:      Vice President and CFO
                                                  ---------------------------


                                     AMSOUTH BANK,
                                     an Alabama banking corporation



                                     By:      /S/ J. S. P. BUCHANAN
                                         ---------------------------
                                         Its:   Vice President
                                                --------------------


                                      -10-