TREX CO INC

Insider Trading Arrangements. During the quarter ended December 31, 2025, none of our directors or officers (as defined in Rule 16a-1(f) of the Exchange Act) adopted, modified or terminated any contract, instruction or written plan for the purchase or sale of our securities that was intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) of the Exchange Act or any non-Rule 10b5-1 trading arrangement (as identified in Item 408(c) of Regulation S-K).

Retention Agreement. On February 24, 2026, the Company entered into a Retention Agreement with Prithvi S. Gandhi, the Company’s Senior Vice President, Chief Financial Officer, pursuant to which the Company will award restricted stock units (RSUs) to Mr. Gandhi, with the RSUs vesting only if Mr. Gandhi is actively employed by the Company on February 24, 2029 (the Retention Date). The aggregate value of the RSUs is $750,000. The number of RSUs shall be based upon the closing market price of the stock on February 24, 2026.

The RSUs will be granted pursuant to the Trex Company, Inc. 2023 Stock Incentive Plan.

The Retention Agreement provides that the RSUs shall vest, and the cash payment will be made, in the event of the death or disability of the Recipient, if the Company terminates the Recipient’s employment without “cause”, or if the Recipient resigns for “good reason,” prior to the Recipient achieving the applicable Retention Date. For this purpose, “cause” shall mean (i) Recipient’s willful or grossly negligent misconduct, or subversive, disruptive or insubordinate behavior, that is injurious to the Company or that violates Company policy; (ii) Recipient’s embezzlement or misappropriation of funds or property of the Company; (iii) Recipient’s conviction of a felony or the entrance of a plea of guilty or nolo contendere to a felony; (iv) Recipient’s conviction of any crime involving fraud, dishonesty, moral turpitude or breach of trust or the entrance of a plea of guilty or nolo contendere to such a crime; or (v) Recipient’s willful failure or refusal by Recipient to devote Recipient’s full business time (other than on account of disability or approved leave) and attention to the performance of Recipient’s duties and responsibilities if such breach has not been cured within 15 days after written notice thereof is given to the Recipient by the Board, and “good reason” shall mean (i) a material and adverse change in Recipient’s status or position(s) as an officer or management employee of the Company, including, without limitation, any adverse change in his status or position as an employee of the Company as a result of a material diminution in Recipient’s duties or responsibilities (other than, if applicable, any such change directly attributable to the fact that the Company is no longer publicly owned) or the assignment to Recipient of any duties or responsibilities which are materially inconsistent with such status or position(s) (other than any isolated and inadvertent failure by the Company that is cured promptly upon his giving notice), or any removal of Recipient from or any failure to reappoint or reelect Recipient to such position(s) (except in connection with Recipient’s termination other than for good reason); (ii) a 10% or greater reduction in Recipient’s aggregate base salary and targeted bonus, other than any such reduction proportionately consistent with a general reduction of pay across the executive staff as a group, as an economic or strategic measure due to poor financial performance by the Company; (iii) the failure by the Company or any successor to continue in effect any material employee benefit plan (excluding any equity compensation plan) in which the Recipient is participating (or plans providing the Recipient with similar benefits that are not materially reduced in the aggregate) other than as a result of the normal expiration of any such plan in accordance with its terms; or the taking of any action, or the failure to act, by the Company or any successor which would adversely affect the Recipient’s continued participation in any of such plans on at least as favorable a basis to Recipient or which would materially reduce Recipient’s benefits under any of such plans, or (iv) Company’s requiring Recipient to be based at an office that is both more than 50 miles from where Recipient’s office is located and further from Recipient’s then current residence.

The Board of Directors has implemented this Retention Agreement reflecting their confidence in Mr. Gandhi’s ability to continue to provide outstanding results and encourage him to continue to focus on the current and future growth of the Company.

The foregoing description of the Retention Agreement is qualified in its entirety by reference to the full text of the Retention Agreement, which is filed as Exhibit 10.10 hereto.