Exhibit 5.1


                     [LETTERHEAD OF HOGAN & HARTSON L.L.P.]


                                  March 8, 2002

Board of Directors
Trex Company, Inc.
160 Exeter Drive
Winchester, VA  22603

Members of the Board of Directors:

          This firm has acted as special counsel to Trex Company, a Delaware
corporation (the "Company"), in connection with its registration, pursuant to a
registration statement on Form S-8 (the "Registration Statement"), of 900,000
shares (the "Shares") of common stock, par value $.01 per share, of the Company,
issuable under the Trex Company, Inc. 1999 Stock Option and Incentive Plan (the
"Plan"). This letter is furnished to you at your request to enable you to
fulfill the requirements of Item 601(b)(5) of Regulation S-K, 17 C.F.R. ss.
229.601(b)(5), in connection with such registration.

          For purposes of this opinion letter, we have examined copies of the
following documents:

          1.   An executed copy of the Registration Statement.

          2.   A copy of the Plan, as certified by the Secretary of the Company
               on the date hereof as then being complete, accurate and in
               effect.

          3.   The Restated Certificate of Incorporation of the Company, as
               certified by the Secretary of the Company on the date hereof as
               then being complete, accurate and in effect.

          4.   The Amended and Restated By-Laws of the Company, as certified by
               the Secretary of the Company on the date hereof as then being
               complete, accurate and in effect.

          5.   A certificate of good standing of the Company issued by the
               Secretary of State of the State of Delaware dated March 4,
               2002.

          6.   Resolutions of the Board of Directors of the Company adopted on
               March 12, 1999 and February 21, 2002, as certified by the
               Secretary of the Company on the date hereof as then being
               complete, accurate and in effect.





          7.   Resolutions of the stockholders of the Company adopted on March
               12, 1999 and April 7, 1999, as certified by the Secretary of the
               Company on the date hereof as then being complete, accurate and
               in effect.

          8.   A certificate of an officer of the Company, dated the date
               hereof, as to certain facts relating to the Company and the Plan.

          In our examination of the aforesaid documents, we have assumed the
genuineness of all signatures, the legal capacity of all natural persons, the
accuracy and completeness of all documents submitted to us, the authenticity of
all original documents, and the conformity to authentic original documents of
all documents submitted to us as copies (including telecopies). This opinion
letter is given, and all statements herein are made, in the context of the
foregoing.

          This opinion letter is based as to matters of law solely on the
Delaware General Corporation Law, as amended. We express no opinion herein as to
any other laws, statutes, ordinances, rules, or regulations. As used herein, the
term "Delaware General Corporation Law, as amended" includes the statutory
provisions contained therein, all applicable provisions of the Delaware
Constitution and reported judicial decisions interpreting these laws.

          Based upon, subject to and limited by the foregoing, we are of the
opinion that following (i) effectiveness of the Registration Statement, (ii)
issuance of the Shares pursuant to the terms contemplated in the Registration
Statement and the Plan and (iii) receipt by the Company of the consideration for
the Shares specified in the resolutions of the Board of Directors (the form of
which is in accordance with applicable law), the Shares will be validly issued,
fully paid, and nonassessable.

          This opinion letter has been prepared for your use in connection with
the Registration Statement and speaks as of the date hereof. We assume no
obligation to advise you of any changes in the foregoing subsequent to the
delivery of this opinion letter.

          We hereby consent to the filing of this opinion letter as Exhibit 5.1
to the Registration Statement. In giving this consent, we do not thereby admit
that we are an "expert" within the meaning of the Securities Act of 1933, as
amended.

                                                     Very truly yours,

                                                    /s/ Hogan & Hartson L.L.P.
                                                    ---------------------------
                                                        HOGAN & HARTSON L.L.P.