X0303 4 2011-03-01 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 2011-03-01 4 M 0 7785 8.80 A 128915 D Common Stock 2011-03-01 4 D 0 2239 30.60 D 126676 D Common Stock 2011-03-01 4 F 0 2342 30.60 D 124334 D Common Stock 2011-03-01 4 S 0 2455 29.92 D 121879 D Common Stock 2011-03-03 4 S 0 630 31.15 D 121249 D Common Stock 2011-03-03 4 S 0 1000 31.20 D 120249 D Common Stock 2011-03-03 4 S 0 100 31.21 D 120149 D Common Stock 2011-03-03 4 S 0 700 31.21 D 119449 D Common Stock 2011-03-03 4 S 0 500 31.22 D 118949 D Common Stock 2011-03-03 4 S 0 174 31.23 D 118775 D Common Stock 2011-03-03 4 S 0 100 31.25 D 118675 D Stock Appreciation Right 8.80 2011-03-01 4 M 0 7785 0 D 2009-01-07 2018-01-07 Common Stock 7785 105877 D 2,239 shares are being surrendered as allowed by the Company's 2005 Stock Incentive Plan to cover the payment of taxes currently due on previously granted restricted shares. 7,785 Stock Appreciation Rights (SARs) are being exercised pursuant to Rule 10b5-1 trading plan adopted by the reporting person on May 10, 2010. 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 May 10, 2010. /s/ William R. Gupp by power of attorney 2011-03-03