X0306 4 2013-10-25 0001069878 TREX CO INC TREX 0001201351 KAPLAN RONALD W C/O TREX COMPANY, INC. 160 EXETER DRIVE WINCHESTER VA 22603-8605 1 1 President and CEO Common Stock 2013-10-25 4 M 0 44950 13.44 A 141176 D Common Stock 2013-10-25 4 M 0 20000 17.41 A 161176 D Common Stock 2013-10-25 4 D 0 14189 67.12 D 146987 D Common Stock 2013-10-25 4 F 0 24214 67.12 D 122773 D Common Stock 2013-10-25 4 S 0 17442 59.95 D 105331 D Common Stock 2013-10-28 4 S 0 26547 67.8161 D 78784 D Stock Appreciation Right 13.44 2013-10-25 4 M 0 44950 0 D 2010-02-18 2019-02-18 Common Stock 44950 4950 D Stock Appreciation Right 17.41 2013-10-25 4 M 0 20000 0 D 2011-02-17 2020-02-17 Common Stock 20000 29900 D 44,950 Stock Appreciation Rights (SARs) are being exercised pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 7, 2013. 20,000 Stock Appreciation Rights (SARs) are being exercised pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 7, 2013. 24,214 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. The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 7, 2013. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $67.75 to $68.115, 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. The stock appreciation right becomes exercisable in three equal installments beginning on the first anniversary of the grant date. /s/ William R. Gupp by power of attorney 2013-10-29