Ownership Submission
FORM 5
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
Form 3 Holdings Reported
Form 4 Transactions Reported
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

ANNUAL STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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1. Name and Address of Reporting Person *
Cox James Mitchell
 2. Issuer Name and Ticker or Trading Symbol
TREX CO INC [TREX] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director _____ 10% Owner
__X__ Officer (give title below) _____ Other (specify below)
Vice President, Sales
(Last)
(First)
(Middle)

C/O TREX COMPANY, INC, 160 EXETER DRIVE		 3. Statement for Issuer's Fiscal Year Ended (Month/Day/Year)
12/31/2012
(Street)


WINCHESTER, VA 22603-8605		 4. If Amendment, Date Original Filed(Month/Day/Year)
 6. Individual or Joint/Group Reporting
(check applicable line)

_X_ Form Filed by One Reporting Person
___ Form Filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)		 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code
(Instr. 8)		 4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)		 5. Amount of Securities Beneficially Owned at end of Issuer's Fiscal Year
(Instr. 3 and 4)		 6. Ownership Form: Direct (D) or Indirect (I)
(Instr. 4)		 7. Nature of Indirect Beneficial Ownership
(Instr. 4)
Amount (A) or (D) Price
Common Stock 08/16/2012   M4 9,700 A $ 24.17 129,047 D  
Common Stock 08/16/2012   M4 6,825 A $ 25.37 135,872 D  
Common Stock 08/16/2012   M4 3,413 A $ 25.37 139,285 D  
Common Stock 08/16/2012   M4 37,049 A $ 9.14 176,334 D  
Common Stock 08/16/2012   M4 21,519 A $ 13.44 197,853 D  
Common Stock 08/16/2012   M4 9,948 A $ 17.41 207,801 D  
Common Stock 08/16/2012   M4 3,515 A $ 26.2 211,316 D  
Common Stock 08/16/2012   D4 47,172 D $ 29.41 164,144 D  
Common Stock 08/16/2012   F4(1) 18,810 D $ 29.41 145,334 D  
Common Stock 08/16/2012   S4 16,909 D $ 29.51 128,425 D  
Common Stock 08/16/2012   S4 10,000 D $ 29.61 118,425 D  
Common Stock 08/17/2012   S4 35,862 D $ 29.97 82,563 D  
Common Stock 08/28/2012   S4 4,044 D $ 30.14 78,519 D  
Common Stock 08/29/2012   S4 3,185 D $ 30.14 75,334 D  
Common Stock 08/29/2012   S4 7,553 D $ 30.29 67,781 D  
Common Stock 08/31/2012   S4 12,447 D $ 30.29 55,334 D  
Common Stock 08/31/2012   S4 20,000 D $ 30.77 35,334 D  
Common Stock 09/13/2012   S4 6,419 D $ 33.26 28,915 D  
Common Stock 09/13/2012   S4 10,000 D $ 33.04 18,915 D  
Common Stock 09/13/2012   S4 359 D $ 33.5 18,556 D  
Common Stock 09/13/2012   S4 18,556 D $ 33.5 0 D  

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number. SEC 2270 (9-02)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 3)		 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code
(Instr. 8)		 5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4, and 5)		 6. Date Exercisable and Expiration Date
(Month/Day/Year)		 7. Title and Amount of Underlying Securities
(Instr. 3 and 4)		 8. Price of Derivative Security
(Instr. 5)		 9. Number of Derivative Securities Beneficially Owned at End of Issuer's Fiscal Year
(Instr. 4)		 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 4)		 11. Nature of Indirect Beneficial Ownership
(Instr. 4)
(A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
Stock Appreciation Right (2) $ 24.17 08/16/2012   M4   9,700 05/07/2009 02/08/2016 Common Stock
9,700
$ 0 0
D
 
Stock Appreciation Right (2) $ 25.37 08/16/2012   M4   6,825 05/07/2009 02/21/2017 Common Stock
6,825
$ 0 0
D
 
Stock Appreciation Right (2) $ 25.37 08/16/2012   M4   3,413 02/21/2010 02/21/2017 Common Stock
3,413
$ 0 0
D
 
Stock Appreciation Right (2) $ 9.14 08/16/2012   M4   37,049 05/07/2011 05/07/2018 Common Stock
37,049
$ 0 0
D
 
Stock Appreciation Right (2) $ 13.44 08/16/2012   M4   21,519 02/18/2010 02/18/2019 Common Stock
21,519
$ 0 0
D
 
Stock Appreciation Right (3) $ 17.41 08/16/2012   M4   9,948 02/17/2011 02/17/2020 Common Stock
9,948
$ 0 4,972
D
 
Stock Appreciation Right (3) $ 26.2 08/16/2012   M4   3,515 02/16/2012 02/16/2022 Common Stock
3,515
$ 0 7,029
D
 

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
Cox James Mitchell
C/O TREX COMPANY, INC
160 EXETER DRIVE
WINCHESTER, VA 22603-8605		       Vice President, Sales  

Signatures

/s/ William R. Gupp by power of attorney 11/26/2012
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) 18,810 shares are being surrendered as allowed by the Company's 2005 Stock Incentive Plan to cover the payment of taxes currently due on the exercise of SARs.
(2) This stock appreciation right is fully exercisable.
(3) This stock appreciation right becomes exercisable in three equal annual installments beginning on the first anniversary of the grant date.

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