X0306 4 2023-02-14 0001069878 TREX CO INC TREX 0001641860 Schemm Dennis Charles 42764 CEDAR RIDGE BLVD CHANTILLY VA 20152 1 SVP, Chief Financial Officer Common Stock 2023-02-14 4 A 0 6076 56.80 A 23431 D Common Stock 2023-02-14 4 A 0 8680 56.80 A 32111 D Common Stock 2023-02-14 4 A 0 1494 56.80 A 33605 D Common Stock 2023-02-14 4 F 0 1890 56.80 D 31715 D Stock Appreciation Right 56.80 2023-02-14 4 A 0 5439 56.80 A 2024-03-01 2033-02-14 Common Stock 5439 5439 D This restricted stock unit vests over a three-year period in three equal annual installments occurring March 1,2024, March 1, 2025 and March 1, 2026. Includes 189 shares acquired under the Company ESPP in March 2022 This restricted stock unit award is performance-based, and vests over a three-year period in three equal installments occurring March 1,2024, March 1, 2025 and March 1, 2026. 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. Represents net share difference between target performance-based shares and actual vested shares, based upon actual performance for the Company. 1,890 shares are being surrendered as allowed by the Company's 2014 Stock Incentive Plan to cover payment of taxes currently due on previously granted restricted stock units. The stock appreciation right becomes exercisable in three equal installments occurring March 1,2024, March 1, 2025 and March 1, 2026. /s/ William R. Gupp by power of attorney 2023-02-16