Amendment to Statement of Changes in Beneficial Ownership (Form 4/A)

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b). Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * Zambanini Adam Dante 2. Issuer Name and Ticker or Trading Symbol TREX CO INC [TREX] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) President and CEO (Last) (First) (Middle) 2500 TREX WAY, C/O TREX COMPANY, INC. 3. Date of Earliest Transaction (Month/Day/Year) 11/05/2026 (Street) WINCHESTER, VA 22601 4. If Amendment, Date Original Filed (Month/Day/Year) 11/09/2026 6. Individual or Joint/Group Filing (Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 11/05/2026 M 1,491(1) A $ 0 236,005 D Common Stock 11/09/2026 S(2) 500 D $55.84(3) 235,505 D

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Stock Appreciation Right

$17.523

11/05/2026

M

2,170(4)

02/15/2018

02/15/2027

Common Stock

2,170

$ 0

0

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Zambanini Adam Dante 2500 TREX WAY C/O TREX COMPANY, INC. WINCHESTER, VA 22601			President and CEO

Signatures

/s/ Amy M. Fernandez by power of attorney		11/09/2026
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Represents 1,491 shares of common stock issued upon settlement of the exercise of 2,170 stock appreciation rights reported in Table II. The number of shares issued was determined based on the excess of the fair market value of the Issuer's common stock on the exercise date over the SAR grant price.
(2)	The shares were sold to satisfy tax obligations arising from the exercise of the stock appreciation rights reported herein.
(3)	The price reported represents the weighted average sale price. The shares were sold in multiple transactions at prices ranging from $55.825 to $55.85, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, information regarding the number of shares sold at each separate price within the range set forth herein.
(4)	Represents the exercise of 2,170 stock appreciation rights. Each stock appreciation right entitled the Reporting Person, upon exercise, to receive the excess of the fair market value of one share of the Issuer's common stock on the exercise date over the SAR grant price of $17.523 per share. Based on a fair market value of $56.01 per share on the exercise date, the exercise was settled through the issuance of 1,491 shares of common stock, as reported in Table I. Following the exercise, no stock appreciation rights remain outstanding under this award.
Remarks: This amendment is being filed solely to correct the price reported in Table I for the acquisition of shares upon settlement of the Reporting Person's stock appreciation rights. The price was inadvertently reported as $56.01 per share, which was the fair market value of the Issuer's common stock used to determine the settlement value of the stock appreciation rights. All other information in the original Form 4 remains unchanged.

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