X0508 4 2026-02-24 0001069878 TREX CO INC TREX 0001791227 Gandhi Prithvi C/O TREX COMPANY, INC. 2500 TREX WAY WINCHESTER VA 22601 1 SVP, Chief Financial Officer 0 Common Stock 2026-02-24 4 A 0 13848 41.45 A 44512 D Common Stock 2026-02-24 4 A 0 13848 41.45 A 58360 D Common Stock 2026-02-24 4 A 0 18094 41.45 A 76454 D This restricted stock unit award vests over a three-year period in three equal annual installments occurring March 1, 2027, March 1, 2028, and March 1, 2029. This restricted stock unit award is performance-based, and vests over a three-year period in three equal installments occurring March 1, 2027, March 1, 2028, and March 1, 2029. The number of shares set forth above is the target number of shares. The number of shares that will actually vest each year will be based upon performance against certain financial goals for the Company and will range from 0% to 200% of the target number of shares. This restricted stock unit award will vest in accordance with the terms of a Retention Agreement, dated February 24, 2026, between Trex Company, Inc. and Prithvi S. Gandhi; as further described in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2025. /s/ Amy M. Fernandez by power of attorney 2026-02-25