TREX CO INC — Director's Dealing 2013

May 3, 2013

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: TREX CO INC (TREX)
CIK: 0001069878
Period of Report: 2013-05-01

Reporting Person: KAPLAN RONALD W (Director, President and CEO)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2013-05-01	Common Stock	M	10300	$9.14	Acquired	115404	Direct
2013-05-01	Common Stock	M	6500	$13.44	Acquired	121904	Direct
2013-05-01	Common Stock	D	3840	$47.27	Disposed	118064	Direct
2013-05-01	Common Stock	F	6183	$47.27	Disposed	111881	Direct
2013-05-01	Common Stock	S	4439	$47.8107	Disposed	107442	Direct
2013-05-03	Common Stock	S	6777	$51.69	Disposed	100665	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2013-05-01	Stock Appreciation Right	$9.14	M	10300	Disposed	2018-05-07	Common Stock (10300)	Direct
2013-05-01	Stock Appreciation Right	$13.44	M	6500	Disposed	2019-02-18	Common Stock (6500)	Direct

Footnotes

F1: 10,300 Stock Appreciation Rights (SARs) are being exercised pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on February 20, 2013.

F2: 6,500 Stock Appreciation Rights (SARs) are being exercised pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on February 20, 2013.

F3: 6,183 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.

F4: The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on February 20, 2013.

F5: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $47.20 to $48.74, inclusive. The reporting person undertakes to provide Trex Company, Inc., any security holder of Trex Company, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in Footnote (5) to this Form 4.

F6: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $50.00 to $52.985, inclusive. The reporting person undertakes to provide Trex Company, Inc., any security holder of Trex Company, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in Footnote (6) to this Form 4.

F7: The stock appreciation right becomes exerciseable in three equal installments beginning on the first anniversary date of the transaction date.

F8: The stock appreciation right becomes exercisable in three equal installments beginning on the first anniversary of the grant date.