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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 JODah+QVrUJSOxTh39l4rWfmAo3YgRhmaZ2Y1yzsnY7f7PPTARsY+HXeba0hVQ63
 XZcXgDbEb9Gu4RVDD0qbCQ==

<SEC-DOCUMENT>0001069878-03-000128.txt : 20031007
<SEC-HEADER>0001069878-03-000128.hdr.sgml : 20031007
<ACCEPTANCE-DATETIME>20031007144518
ACCESSION NUMBER:		0001069878-03-000128
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20031006
FILED AS OF DATE:		20031007

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			WITTENBERG ROGER A
		CENTRAL INDEX KEY:			0001084721

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-14649
		FILM NUMBER:		03931251

	BUSINESS ADDRESS:	
		STREET 1:		C/O TREX COMPANY INC
		STREET 2:		20 SOUTH CAMERON STREET
		CITY:			WINCHESTER
		STATE:			VA
		ZIP:			22801

	MAIL ADDRESS:	
		STREET 1:		TREX COMPANY INC
		STREET 2:		20 SOUTH CAMERON STREET
		CITY:			WINCHESTER
		STATE:			VA
		ZIP:			22801

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			TREX CO INC
		CENTRAL INDEX KEY:			0001069878
		STANDARD INDUSTRIAL CLASSIFICATION:	LUMBER & WOOD PRODUCTS (NO FURNITURE) [2400]
		IRS NUMBER:				541910453
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		20 CAMERON ST
		CITY:			WINCHESTER
		STATE:			VA
		ZIP:			22801
		BUSINESS PHONE:		5406784070

	MAIL ADDRESS:	
		STREET 1:		20 CAMERON ST
		CITY:			WINCHESTER
		STATE:			VA
		ZIP:			22801
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>c0001084721d20031007f4f.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
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<ownershipDocument><schemaVersion>X0201</schemaVersion>    <documentType>4</documentType><periodOfReport>2003-10-06</periodOfReport><notSubjectToSection16>0</notSubjectToSection16><issuer><issuerCik>0001069878</issuerCik><issuerName>TREX CO INC</issuerName>        <issuerTradingSymbol>TWP</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId><rptOwnerCik>0001084721</rptOwnerCik><rptOwnerName>WITTENBERG ROGER A</rptOwnerName></reportingOwnerId><reportingOwnerAddress><rptOwnerStreet1>160 EXETER DRIVE</rptOwnerStreet1><rptOwnerStreet2></rptOwnerStreet2><rptOwnerCity>WINCHESTER</rptOwnerCity><rptOwnerState>VA</rptOwnerState><rptOwnerZipCode>22603-8605</rptOwnerZipCode><rptOwnerStateDescription></rptOwnerStateDescription></reportingOwnerAddress><reportingOwnerRelationship><isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>1</isTenPercentOwner><isOther>0</isOther><officerTitle>Executive VP, Recycling</officerTitle><otherText></otherText></reportingOwnerRelationship></reportingOwner><non
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<natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeTransaction><nonDerivativeTransaction><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-10-06</value></transactionDate><deemedExecutionDate><value>2003-10-06</value></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>100</value></transactionShares><transactionPricePerShare><value>31.5</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1473250</value><footnoteId id="F1"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirec
tOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeTransaction><nonDerivativeTransaction><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-10-06</value></transactionDate><deemedExecutionDate><value>2003-10-06</value></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>100</value></transactionShares><transactionPricePerShare><value>31.52</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1473150</value><footnoteId id="F1"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></dir
ectOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeTransaction><nonDerivativeTransaction><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-10-06</value></transactionDate><deemedExecutionDate><value>2003-10-06</value></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>100</value></transactionShares><transactionPricePerShare><value>31.96</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1473050</value><footnoteId id="F1"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D<
/value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeTransaction></nonDerivativeTable><derivativeTable></derivativeTable><footnotes><footnote id="F1">Does not include Indirect Beneficial Ownership of 3000 shares by wife. Mr. Wittenberg disclaims beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for purposes of Section 16 or any other purpose.</footnote></footnotes><ownerSignature><signatureName>Lynn E. MacDonald</signatureName><signatureDate>2003-10-07</signatureDate></ownerSignature></ownershipDocument>

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</SEC-DOCUMENT>
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