TREX

This restricted stock unit award will vest on the first anniversary of the grant.

This restricted stock unit award will vest on the first anniversary of the grant.

The reported transaction was effected pursuant to a plan adopted by the reporting person on March 5, 2026, in accordance with Rule 10b5-1 of the Securities Exchange Act of 1934 (the "10b5-1 Plan"). The 10b5-1 Plan provides for automatic sales of shares according to pre-established instructions. The reporting person sold 1,400 shares in a single trade at a price of $50.00 per share. All 1,400 shares under the 10b5-1 Plan have been sold.

This restricted stock unit award will vest on the first anniversary of the grant.

This restricted stock unit award will vest on the first anniversary of the grant.

The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $40.54 to $40.86, inclusive. The reporting person undertakes to provide to Issuer, any security holder of Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in footnote (3) to this Form 4.

The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $39.84 to $40.34, inclusive. The reporting person undertakes to provide to Issuer, any security holder of Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in footnote (2) to this Form 4.

The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $40.13 to $40.33, inclusive. The reporting person undertakes to provide to Issuer, any security holder of Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in footnote (1) to this Form 4.

4.496 shares are being surrendered as allowed by the Company's 2023 Stock Incentive Plan to cover payment of taxes currently due on previously granted restricted stock units.

Represents the target number of performance-based restricted units which did not vest due to the performance condition not being satisfied.

Represents net share difference between target performance-based shares and actual vested shares, based upon actual performance of the Company.

23,127 shares are being surrendered as allowed by the Company's 2023 Stock Incentive Plan to cover payment of taxes currently due on previously granted restricted stock units.

Represents net share difference between target performance-based shares and actual vested shares, based upon actual performance of the Company.

8,271 shares are being surrendered as allowed by the Company's 2023 Stock Incentive Plan to cover payment of taxes currently due on previously granted restricted stock units.

Represents the target number of performance-based restricted units which did not vest due to the performance condition not being satisfied.

Represents net share difference between target performance-based shares and actual vested shares, based upon actual performance of the Company.

Represents the target number of performance-based restricted units which did not vest due to the performance condition not being satisfied.

2,850 shares are being surrendered as allowed by the Company's 2023 Stock Incentive Plan to cover payment of taxes currently due on previously granted restricted stock units.

Represents net share difference between target performance-based shares and actual vested shares, based upon actual performance of the Company.

Represents the target number of performance-based restricted units which did not vest due to the performance condition not being satisfied.

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 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 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 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 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.

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 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 on the first anniversary of the grant.

This restricted stock unit award will vest on the first anniversary of the grant.

This restricted stock unit award will vest on the first anniversary of the grant.

This restricted award will vest on the first anniversary of the grant.

The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $31.835 to $31.93, inclusive. The reporting person undertakes to provide to Issuer, any security holder of Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in footnote (1) to this Form 4.

This restricted stock unit award cliff vests on October 6, 2028.

This restricted stock unit award will vest in accordance with the terms of a Retention Agreement, dated October 30, 2025, between Trex Company, Inc. and Amy M. Fernandez; as further described in the Company's Quarterly Report on Form 10-Q for the quarterly period ended on September 30, 2025.

Shares were purchased through the Trex Company, Inc. Amended and Restated 1999 Employee Stock Purchase Plan

This restricted stock unit award will vest on the first anniversary of the grant.

This restricted stock unit award will vest on the first anniversary of the grant.

The price reported in column 4 is a weighted average price These shares were sold in multiple transactions at prices ranging from $64.17 to $64.19, inclusive.

This transaction involved a gift by the reporting person to a charitable organization as described in Section 501(c)(3) of the Internal Revenue Code.

This restricted stock unit award will vest on the first anniversary of the grant.

This restricted stock unit award will vest on the first anniversary of the grant.

This restricted stock unit award will vest on the first anniversary of the grant.

This restricted stock unit award will vest on the first anniversary of the grant.

This restricted stock unit award will vest on the first anniversary of the grant.

This restricted stock unit award will vest on the first anniversary of the grant.