X0306 4 2012-11-02 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 2012-11-02 4 M 0 57921 9.14 A 187019 D Common Stock 2012-11-02 4 D 0 13478 39.28 D 173541 D Common Stock 2012-11-02 4 F 0 18755 39.28 D 154786 D Common Stock 2012-11-02 4 S 0 18067 39.00 D 136719 D Common Stock 2012-11-02 4 S 0 800 39.01 D 135919 D Common Stock 2012-11-02 4 S 0 1150 39.02 D 134769 D Common Stock 2012-11-02 4 S 0 200 39.03 D 134569 D Common Stock 2012-11-06 4 S 0 24588 39.45 D 109981 D Common Stock 2012-11-06 4 S 0 400 39.46 D 109581 D Common Stock 2012-11-06 4 S 0 600 39.47 D 108981 D Common Stock 2012-11-06 4 S 0 100 39.48 D 108881 D Stock Appreciation Right 9.14 2012-11-02 4 M 0 57921 0 D 2009-05-07 2018-05-07 Common Stock 57921 26300 D 57,921 Stock Appreciation Rights (SARs) are being exercised pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on July 31, 2012. 18,755 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 Rule 10b5-1 trading plan adopted by the reporting person on July 31, 2012. The stock appreciation right becomes exerciseable in three equal installments beginning on the first anniversary date of the transaction date. /s/ William R. Gupp by power of attorney 2012-11-05