X0305 4 2012-04-02 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 2012-04-02 4 M 0 34000 8.80 A 149856 D Common Stock 2012-04-02 4 D 0 9376 31.91 D 140480 D Common Stock 2012-04-02 4 F 0 10392 31.91 D 130088 D Common Stock 2012-04-02 4 S 0 8000 31.3125 D 122088 D Common Stock 2012-04-04 4 S 0 14232 31.2548 D 107856 D Stock Appreciation Right 8.80 2012-04-02 4 M 0 34000 0 D 2009-01-07 2018-01-07 Common Stock 34000 23355 D 34,000 Stock Appreciation Rights (SARs) are being exercised pursuant to Rule 10b5-1 trading plan adopted by the reporting person on November 1, 2011. 10,392 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 stock appreciation right becomes exerciseable in three equal installments beginning on the first anniversary date of the transaction date. The sales reported in this Form 4 were effected pursuant to Rule 10b5-1 trading plan adopted by the reporting person on November 1, 2011. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $31.06 to $31.65, 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 price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $30.97 to $31.42, 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. /s/ William R. Gupp by power of attorney 2012-04-04