X0303 4 2011-04-01 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 2011-04-01 4 M 0 16173 8.80 A 134848 D Common Stock 2011-04-01 4 D 0 4270 33.33 D 130578 D Common Stock 2011-04-01 4 F 0 5025 33.33 D 125553 D Common Stock 2011-04-01 4 S 0 100 32.80 D 125453 D Common Stock 2011-04-01 4 S 0 100 32.82 D 125353 D Common Stock 2011-04-01 4 S 0 100 32.84 D 125253 D Common Stock 2011-04-01 4 S 0 200 32.86 D 125053 D Common Stock 2011-04-01 4 S 0 100 32.88 D 124953 D Common Stock 2011-04-01 4 S 0 417 32.90 D 124536 D Common Stock 2011-04-01 4 S 0 100 32.93 D 124436 D Common Stock 2011-04-01 4 S 0 100 32.96 D 124336 D Common Stock 2011-04-04 4 S 0 1040 33.16 D 123296 D Common Stock 2011-04-04 4 S 0 460 33.17 D 122836 D Common Stock 2011-04-04 4 S 0 17 33.175 D 122819 D Common Stock 2011-04-04 4 S 0 600 33.18 D 122219 D Common Stock 2011-04-04 4 S 0 200 33.185 D 122019 D Common Stock 2011-04-04 4 S 0 500 33.19 D 121519 D Common Stock 2011-04-04 4 S 0 100 33.1925 D 121419 D Common Stock 2011-04-04 4 S 0 200 33.20 D 121219 D Common Stock 2011-04-04 4 S 0 100 33.21 D 121119 D Common Stock 2011-04-04 4 S 0 483 33.22 D 120636 D Common Stock 2011-04-04 4 S 0 100 33.2325 D 120536 D Common Stock 2011-04-04 4 S 0 2173 33.24 D 118363 D Common Stock 2011-04-04 4 S 0 100 33.245 D 118263 D Common Stock 2011-04-04 4 S 0 300 33.2475 D 117963 D Common Stock 2011-04-04 4 S 0 200 33.249 D 117763 D Common Stock 2011-04-04 4 S 0 305 33.25 D 117458 D Stock Appreciation Right 8.80 2011-04-01 4 M 0 16173 0 D 2009-01-07 2018-01-07 Common Stock 16173 89704 D 16,173 Stock Appreciation Rights (SARs) are being exercised pursuant to Rule 10b5-1 trading plan adopted by the reporting person on November 3, 2010. 5,025 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 3, 2010. /s/ William R. Gupp by power of attorney 2011-04-05