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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 F7RpFLnpqP1dghHbDt3e1whOG88nb461kubqh3dNXmMTndZqUWeYwgYEd2Y0teGN
 7S2JfZ6snGPjN7yt0j568g==

<SEC-DOCUMENT>0001069878-04-000016.txt : 20040114
<SEC-HEADER>0001069878-04-000016.hdr.sgml : 20040114
<ACCEPTANCE-DATETIME>20040114175436
ACCESSION NUMBER:		0001069878-04-000016
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20040101
FILED AS OF DATE:		20040114

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			FERRARI ANDREW U
		CENTRAL INDEX KEY:			0001105737

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-14649
		FILM NUMBER:		04525839

	BUSINESS ADDRESS:	
		STREET 1:		C/O TREX CO
		STREET 2:		20 SOUTH CAMERON ST
		CITY:			WINCHESTER
		STATE:			VA
		ZIP:			22601

	MAIL ADDRESS:	
		STREET 1:		C/O TREX CO
		STREET 2:		20 SOUTH CAMERON ST
		CITY:			WINCHESTER
		STATE:			VA
		ZIP:			22601

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>c0001105737d20040114f4f.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<ownershipDocument><schemaVersion>X0201</schemaVersion>    <documentType>4</documentType><periodOfReport>2004-01-01</periodOfReport><notSubjectToSection16>0</notSubjectToSection16><issuer><issuerCik>0001069878</issuerCik><issuerName>TREX CO INC</issuerName>        <issuerTradingSymbol>TWP</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId><rptOwnerCik>0001105737</rptOwnerCik><rptOwnerName>FERRARI ANDREW U</rptOwnerName></reportingOwnerId><reportingOwnerAddress><rptOwnerStreet1>828 ARMISTEAD STREET</rptOwnerStreet1><rptOwnerStreet2></rptOwnerStreet2><rptOwnerCity>WINCHESTER</rptOwnerCity><rptOwnerState>VA</rptOwnerState><rptOwnerZipCode>22601</rptOwnerZipCode><rptOwnerStateDescription></rptOwnerStateDescription></reportingOwnerAddress><reportingOwnerRelationship><isDirector>1</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle></officerTitle><otherText></otherText></reportingOwnerRelationship></reportingOwner><nonDerivativeTable></nonDeriv
ativeTable><derivativeTable><derivativeTransaction><securityTitle><value>Stock Options (Right to buy)</value></securityTitle><conversionOrExercisePrice><value>21.48</value></conversionOrExercisePrice><transactionDate><value>2004-01-01</value></transactionDate><deemedExecutionDate></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>233</value></transactionShares><transactionPricePerShare><value>0</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2005-01-01</value></exerciseDate><expirationDate><value>2014-01-01</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>233</value></underlyingSecurityShares></underlyingSecurity><postTr
ansactionAmounts><sharesOwnedFollowingTransaction><value>233</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeTransaction></derivativeTable><footnotes></footnotes><ownerSignature><signatureName>Lynn E. MacDonald</signatureName><signatureDate>2004-01-14</signatureDate></ownerSignature></ownershipDocument>

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</SEC-DOCUMENT>
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