How do I Replace Deck Boards With Trex Decking?

Replacing your existing deck's boards with Trex offers more than a facelift.

Trex decking is an attractive alternative building material invulnerable to wood's weaknesses, such as rot and mold. Trex won't even require periodic refinishing with paint or stain. Trex has the beauty, versatility and texture of wood, but it is a composite made from recycled plastic and wood fibers that eliminates costly maintenance requirements. Trex installation uses the same tools and methods as standard decking. .

Remove the existing deck boards to expose the joists. Inspect the existing deck substructure for weakness or damage, and repair as necessary. Clear the top surface of the joists of any old nails, splintering or other imperfections that might interfere with the Trex decking material laying flat and level.

Measure the width of the Trex decking boards being installed plus 1/2 inch. From the starting edge of the deck, make a mark for this measurement at both ends of the deck, then use a chalk line to connect the two marks. This will be the guideline for the first row of Trex decking.

Lay full lengths of Trex decking boards, end to end, aligned with the first row guideline marked in Step 2, then cut the board ends, as needed, to keep each end joint centered on a joist. Note: Breaking the end joints on joist supports the joints. Use this method for all end joints over the entire deck.

Install the first row of Trex decking boards by aligning the edge with the guideline marked in Step 2, then inserting two 2-inch plated decking screws vertically through the board into the center line of each joist, spacing the screws approximately 1 inch from the board's edge.

Repeat Step 4 from the subsequent rows of Trex decking boards, spacing the rows of boards a minimum of 1/4 inch apart and staggering the end joint locations by a minimum of 32 inches. For decking strength and appearance, the end joints of any two adjacent rows should never fall on the same joist.

Install the Trex deck fascia boards, if applicable, to the perimeter rim joists, keeping the top of the fascia boards flush with the deck surface to conceal the decking end cuts.

Things You Will Need

  • Tape measure
  • Chalk line
  • Circular saw or power miter saw
  • Cordless screwdriver
  • 2-by-6 Trex decking
  • 2-inch plated decking screws
  • 1/4-inch plywood blocks (optional)


  • Using a small block of 1/4-inch plywood between the Trex decking as its being secured is an efficient alternative to using a tape to measure the spacing.


  • The manufacturer of Trex recommends that the decking joist spacing not exceed 16 inches to maintain structural support for the decking boards.

About the Author

Paul Massey has been writing since 2009, drawing on a 35-year career in the construction industry. His experience includes 15 years as a general building contractor specializing in architectural design, custom homes, commercial development and historic renovations.