**Exhibit 4.11**SIXTH AMENDMENT TO CREDIT AGREEMENT     THIS SIXTH AMENDMENT TO CREDIT AGREEMENT (this “Sixth Amendment”), dated as of May27, 2005, is entered into among ELKCORP (formerly known as Elcor Corporation), a Delawarecorporation (the “Borrower”), the lenders listed on the signature pages hereof as Lenders(the “Lenders”), BANK ONE, N.A., as Documentation Agent, and BANK OF AMERICA, N.A., asAdministrative Agent, Swing Line Lender and L/C Issuer.BACKGROUND     A. The Borrower, certain of the Lenders, the Documentation Agent, the Syndication Agent, theAdministrative Agent, the Swing Line lender and the L/C Issuer are parties to that certain CreditAgreement, dated as of November 30, 2000, as amended by that certain First Amendment to CreditAgreement, dated as of March 31, 2001, that certain Second Amendment to Credit Agreement, dated asof June 5, 2002, that certain Third Amendment to Credit Agreement, dated as of February 20, 2003,that certain Fourth Amendment to Credit Agreement, dated as of March 7, 2003, and that certainFifth Amendment to Credit Agreement, dated as of December 5, 2003 (said Credit Agreement, asamended, the “Credit Agreement”). The terms defined in the Credit Agreement and nototherwise defined herein shall be used herein as defined in the Credit Agreement.     B. The Borrower has requested certain amendments to the Credit Agreement.     C. The Lenders, the Documentation Agent, the Administrative Agent, the Swing Line Lender andthe L/C Issuer hereby agree to amend the Credit Agreement, subject to the terms and conditions setforth herein.     NOW, THEREFORE, in consideration of the covenants, conditions and agreements hereafter setforth, and for other good and valuable consideration, the receipt and adequacy of which are allhereby acknowledged, the Borrower, the Lenders, the Swing Line Lender, the L/C Issuer and theAdministrative Agent covenant and agree as follows:     1. AMENDMENTS.     (a) Section 5.17 of the Credit Agreement is hereby amended to read as follows:     **5.17 Businesses.**The Borrower is engaged and may engage in the future,directly or through wholly-owned Subsidiaries, in the following businesses: (a) themanufacture of premium building materials, including (i) premium roofing products,including laminated fiberglass asphalt shingles and accessory products, (ii)performance non-woven fabrics, including coated and uncoated fiberglass mat, matproducts, and other non-woven materials; (iii) composite building products,including decking, fencing, railing, building product structural components andaccessories and (iv) and such other building products business platforms to extendits premium building products business; (b) the manufacturing, recycling andremanufacturing of diesel engine power assemblies, cylinder liners, heads, rods,waterjackets, valves, pistons and related
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components, including hard chrome plating of cylinder bores, primarily for therailroad and marine industries; hard chrome plating of original equipment cylinderliners for major domestic locomotive manufacturers and stationary power equipmentmanufacturers, the electrolessplating of nonmetallic computer and other electronicenclosures to provide electromagnetic and radio frequency interference protection,and the development of new products for its proprietary nickel, tin, iron and hardchrome plated finishes; and (c) the sale of patent licenses with engineering supportservices and the sale of consulting engineering services to the oil and gasproduction, gas processing and sulfur recovery industries.     (b) Section 7.03 of the Credit Agreement is hereby amended to add a new clause (c)thereto to read as follows:     (c) the Borrower or any Subsidiary may make any Disposition permitted underSection 7.04.     (c) Sections 7.04(d) and (e) of the Credit Agreement are hereby amended toread as follows:     (d) Dispositions of capital stock or all or substantially all of the assets ofany Subsidiary not engaged in the businesses described in Section 5.17(a)(i)or 5.17(a)(ii);     (e) **[Intentionally Omitted]**; and     (d) Section 7.04 of the Credit Agreement is hereby amended by adding a new clause (f)thereto to read as follows:     (f) Dispositions of property by (i) any Subsidiary to the Borrower or to aGuarantor or (ii) the Borrower to any Guarantor;     (e) Article IX of the Credit Agreement is hereby amended by adding a new Section9.13 thereto to read as follows:     **9.13 Guaranty Matters.**Effective automatically and immediately at the timethat any Guarantor ceases to be a Subsidiary or all or substantially all of theassets of any Guarantor are Disposed of, in either case as a result of a transactionpermitted hereunder and provided that such Guarantor is released from all GuarantyObligations in respect of any other Indebtedness of the Borrower, such Guarantorshall be released from its Guaranty. Notwithstanding anything in Section10.01 to the contrary, the Lenders and the L/C Issuer irrevocably authorize theAdministrative Agent to evidence the release of any Guarantor from its obligationsunder any Guaranty as a result of either event set forth in the immediatelypreceding sentence.
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     2. REPRESENTATIONS AND WARRANTIES TRUE; NO EVENT OF DEFAULT. By its execution anddelivery hereof, the Borrower represents and warrants that, as of the date hereof:     (a) the representations and warranties contained in the Credit Agreement and the other LoanDocuments are true and correct on and as of the date hereof as made on and as of such date;     (b) no event has occurred and is continuing which constitutes a Default or an Event ofDefault;     (c) (i) the Borrower has full power and authority to execute and deliver this Sixth Amendment,(ii) this Sixth Amendment has been duly executed and delivered by the Borrower, and (iii) thisSixth Amendment and the Credit Agreement, as amended hereby, constitute the legal, valid andbinding obligations of the Borrower, enforceable in accordance with their respective terms, exceptas enforceability may be limited by applicable debtor relief laws and by general principles ofequity (regardless of whether enforcement is sought in a proceeding in equity or at law) and exceptas rights to indemnity may be limited by federal or state securities laws;     (d) neither the execution, delivery and performance of this Sixth Amendment or the CreditAgreement, as amended hereby, nor the consummation of any transactions contemplated herein ortherein, will conflict with any Law or Organization Documents of the Borrower, or any indenture,agreement or other instrument to which the Borrower or any of its property is subject; and     (e) no authorization, approval, consent, or other action by, notice to, or filing with, anygovernmental authority or other Person not previously obtained is required for the execution,delivery or performance by the Borrower of this Sixth Amendment.     3. CONDITIONS TO EFFECTIVENESS. This Sixth Amendment shall be effective uponsatisfaction or completion of the following:     (a) the Administrative Agent shall have received counterparts of this Sixth Amendment executedby the Required Lenders;     (b) the Administrative Agent shall have received counterparts of this Sixth Amendment executedby the Borrower and acknowledged by each Guarantor; and     (c) the Administrative Agent shall have received, in form and substance satisfactory to theAdministrative Agent and its counsel, such other documents, certificates and instruments as theAdministrative Agent shall require.
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     4. REFERENCE TO THE CREDIT AGREEMENT.     (a) Upon the effectiveness of this Sixth Amendment, each reference in the Credit Agreement to“this Agreement”, “hereunder”, or words of like import shall mean and be a reference to the CreditAgreement, as affected and amended hereby.     (b) The Credit Agreement, as amended by the amendments referred to above, shall remain in fullforce and effect and is hereby ratified and confirmed.     5. COSTS, EXPENSES AND TAXES. The Borrower agrees to pay on demand all costs andexpenses of the Administrative Agent in connection with the preparation, reproduction, executionand delivery of this Sixth Amendment and the other instruments and documents to be deliveredhereunder (including the reasonable fees and out-of-pocket expenses of counsel for theAdministrative Agent with respect thereto).     6. GUARANTOR’S ACKNOWLEDGMENT. By signing below, each Guarantor (a) acknowledges,consents and agrees to the execution, delivery and performance by the Borrower of this SixthAmendment, (b) acknowledges and agrees that its obligations in respect of its Guaranty (i) are notreleased, diminished, waived, modified, impaired or affected in any manner by this Sixth Amendmentor any of the provisions contemplated herein, (c) ratifies and confirms its obligations under itsGuaranty, and (d) acknowledges and agrees that it has no claims or offsets against, or defenses orcounterclaims to, its Guaranty, including the release of OEL, Ltd. from its obligation under anyGuaranty.     7. EXECUTION IN COUNTERPARTS. This Sixth Amendment may be executed in any number ofcounterparts and by different parties hereto in separate counterparts, each of which when soexecuted and delivered shall be deemed to be an original and all of which when taken together shallconstitute but one and the same instrument. For purposes of this Sixth Amendment, a counterparthereof (or signature page thereto) signed and transmitted by any Person party hereto to theAdministrative Agent (or its counsel) by facsimile machine, telecopier or electronic mail is to betreated as an original. The signature of such Person thereon, for purposes hereof, is to beconsidered as an original signature, and the counterpart (or signature page thereto) so transmittedis to be considered to have the same binding effect as an original signature on an originaldocument.     8. GOVERNING LAW; BINDING EFFECT. This Sixth Amendment shall be governed by andconstrued in accordance with the laws of the State of Texas applicable to agreements made and to beperformed entirely within such state, provided that each party shall retain all rights arisingunder federal law, and shall be binding upon the parties hereto and their respective successors andassigns.     9. HEADINGS. Section headings in this Sixth Amendment are included herein forconvenience of reference only and shall not constitute a part of this Sixth Amendment for any otherpurpose.     10. ENTIRE AGREEMENT. THE CREDIT AGREEMENT, AS AMENDED BY THIS SIXTH AMENDMENT, ANDTHE OTHER LOAN DOCUMENTS REPRESENT THE
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FINAL AGREEMENT BETWEEN THE PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR,CONTEMPORANEOUS, OR SUBSEQUENT ORAL AGREEMENTS BETWEEN THE PARTIES. THERE ARE NO UNWRITTEN ORALAGREEMENTS BETWEEN THE PARTIES.
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     IN WITNESS WHEREOF, this Sixth Amendment is executed as of the date first set forth above.           **ELKCORP**             By:                 Name:                 Title:             
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           **BANK OF AMERICA, N.A.**, as Administrative    Agent             By:                 Name:                 Title:             
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           **BANK OF AMERICA, N.A**., as a Lender, L/C    Issuer and Swing Line Lender             By:                 Name:                 Title:             
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           **JPMORGAN CHASE BANK, N.A.**, as a Lender    and Documentation Agent             By:                 Name:                 Title:             
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           **THE NORTHERN TRUST COMPANY**, as a    Lender             By:                 Name:                 Title:             
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           **WELLS FARGO BANK, NATIONAL**    **ASSOCIATION**, as a Lender             By:                 Name:                 Title:             
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           **COMPASS BANK**, as a Lender             By:                 Name:                 Title:             
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           **HIBERNIA NATIONAL BANK**, as a Lender             By:                 Name:                 Title:             
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           **BRANCH BANKING AND TRUST**    **COMPANY**, as a Lender             By:                 Name:                 Title:             
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           **KEYBANK NATIONAL ASSOCIATION**, as a    Lender             By:                 Name:                 Title:             
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ACKNOWLEDGED AND AGREED TO:ELK PREMIUM BUILDING PRODUCTS, INC.     (formerly known as Elk Corporation of Dallas)ELK CORPORATION OF TEXAS