-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 J6Z4KaUWiz8Jp2zR3D5HsVKX3KS4z+PC6WgWRHoQpvW1Qq8Tr9xPQX7hf88x0ZEz
 kVDs2lvk0EniB44tM1tkng==

<SEC-DOCUMENT>0001253260-03-000026.txt : 20030724
<SEC-HEADER>0001253260-03-000026.hdr.sgml : 20030724
<ACCEPTANCE-DATETIME>20030724145739
ACCESSION NUMBER:		0001253260-03-000026
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030722
FILED AS OF DATE:		20030724

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:		03800814

	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>c0001084721d20030724f4s1f.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
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<ownershipDocument><schemaVersion>X0101</schemaVersion>    <documentType>4</documentType><periodOfReport>2003-07-22</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>  </rptOwnerStreet1><rptOwnerStreet2>  </rptOwnerStreet2><rptOwnerCity>  </rptOwnerCity><rptOwnerState>  </rptOwnerState><rptOwnerZipCode>  </rptOwnerZipCode></reportingOwnerAddress><reportingOwnerRelationship><isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>1</isTenPercentOwner><isOther>0</isOther><officerTitle>Executive VP, Recycling</officerTitle><otherText></otherText></reportingOwnerRelationship></reportingOwner><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTitle><tra
nsactionDate><value>2003-07-22</value><footnoteId id="F1"/></transactionDate><deemedExecutionDate><value>2003-07-22</value></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>100</value></transactionShares><transactionValue><value>36.76</value></transactionValue><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1534300</value><footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securit
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ansactionDate><value>2003-07-22</value></transactionDate><deemedExecutionDate><value>2003-07-22</value></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>100</value></transactionShares><transactionValue><value>37.41</value></transactionValue><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1534100</value><footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTitle><transactionD
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>2003-07-22</value></transactionDate><deemedExecutionDate><value>2003-07-22</value></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>100</value></transactionShares><transactionValue><value>37.23</value></transactionValue><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1533900</value><footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-07-2
2</value></transactionDate><deemedExecutionDate><value>2003-07-15</value></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>100</value></transactionShares><transactionValue><value>38</value></transactionValue><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1533800</value><footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-07-22</value></tr
ansactionDate><deemedExecutionDate><value>2003-07-22</value></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>150</value></transactionShares><transactionValue><value>37.92</value></transactionValue><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1533650</value><footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-07-22</value></transactionD
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dExecutionDate><value>2003-07-22</value></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>100</value></transactionShares><transactionValue><value>37.15</value></transactionValue><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1533450</value><footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-07-22</value></transactionDate><deemedExecution
Date><value>2003-07-22</value></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>100</value></transactionShares><transactionValue><value>37.12</value></transactionValue><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1533350</value><footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-07-22</value></transactionDate><deemedExecutionDate><valu
e>2003-07-22</value></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>100</value></transactionShares><transactionValue><value>36.63</value></transactionValue><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1533250</value><footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-07-22</value></transactionDate><deemedExecutionDate><value>2003-07-
22</value></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>100</value></transactionShares><transactionValue><value>36.69</value></transactionValue><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1533150</value><footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-07-22</value></transactionDate><deemedExecutionDate><value>2003-07-22</value>
</deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>100</value></transactionShares><transactionValue><value>37.15</value></transactionValue><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1533050</value><footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><footnotes><footnote id="F1">Additional transactions by the reporting person for this date are being reported on a separate Form 4.</footnote><footnote id="F2">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>Evan R. Farber</signatureName><signatureDate>2003-07-24</signatureDate></ownerSignature></ownershipDocument>

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</DOCUMENT>
</SEC-DOCUMENT>
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