How to Seal Trex Decking

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Things You'll Need

  • Rubber gloves

  • Oxygen bleach

  • Coarse plastic brush

  • Pressure washer

  • Acrylic composite deck sealer

  • 5-gallon bucket

  • Roller frame

  • Foam roller cover

  • Roller extension pole

  • 4-inch nylon paintbrush

Trex is a brand of wood-plastic composite decking made of sawdust and recycled plastics such as plastic grocery bags. Unlike solid wood decking which is porous, Trex is waterproof. This characteristic makes it resistant to warping and rot. Unfortunately, Trex stains relatively easily and tends to accumulate mildew and mold. A quality sealer will protect your Trex decking from these types of problems. Learn the proper prep and application procedure before applying a sealer to your deck.


Step 1

Put on rubber gloves.

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Step 2

Scrub dark spots and areas of mold and mildew using an oxygen bleach. Use a pressure washer to rinse the entire Trex decking. Repeat until the Trex looks bright and clean. Let the decking dry for a full day.

Step 3

Pour 2 gallons of acrylic composite deck sealer into a 5-gallon bucket. Use a roller to apply the sealer to the Trex decking. Don't work from your knees; ease the process by attaching the roller to an extension pole. Don't trap yourself behind wet sealer. Begin at the far end of the deck and work backward toward the door or decking steps.


Step 4

Use a nylon brush to touch up skipped areas. Let the Trex dry for two hours.

Step 5

Pour the remaining sealer back into the can. Clean the bucket and brush with water.


One gallon of acrylic composite deck sealer will coat about 350 to 400 square feet of Trex decking.


Don't apply the acrylic composite deck sealer until you have thoroughly cleaned the Trex, or flaking and peeling will occur.


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