X0306 4 2013-04-04 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 2013-04-04 4 S 0 100 46.12 D 111779 D Common Stock 2013-04-04 4 S 0 112 46.22 D 111667 D Common Stock 2013-04-04 4 S 0 4463 46.50 D 107204 D Common Stock 2013-04-04 4 S 0 200 46.55 D 107004 D Common Stock 2013-04-04 4 S 0 200 46.56 D 106804 D Common Stock 2013-04-04 4 S 0 300 46.58 D 106504 D Common Stock 2013-04-04 4 S 0 100 46.60 D 106404 D Common Stock 2013-04-04 4 S 0 100 46.61 D 106304 D Common Stock 2013-04-04 4 S 0 200 46.79 D 106104 D Common Stock 2013-04-04 4 S 0 300 46.63 D 105804 D Common Stock 2013-04-04 4 S 0 500 46.81 D 105304 D Common Stock 2013-04-04 4 S 0 100 46.80 D 105204 D Common Stock 2013-04-04 4 S 0 100 46.82 D 105104 D The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on February 20, 2013. /s/ William R. Gupp by power of attorney 2013-04-04