How to Clean a Composite Deck (Trex and Similar)

Composite is not wood

A composite deck looks like wood, but it is boards made from wood fiber and plastic. It does not go gray and splinter the way bare wood does, so the advice for cleaning a wood deck does not carry over. The surface can be lightened by the wrong chemical and damaged by too much pressure, and each maker sets its own limits.

What Trex says

Trex publishes its own care and cleaning rules (Trex care and cleaning):

• Routine cleaning: hose off loose debris, then scrub with warm soapy water and a soft brush. For its newer, higher performance lines, soap and water or gentle pressure washing is enough.
• Pressure washing, Transcend, Enhance and Select: a washer no greater than 3,100 psi, with a fan attachment, and the fan tip no closer than 8 inches from the surface. Rinse thoroughly.
• Early generation Trex (Accents, Origins): Trex does not recommend a pressure washer at all, and suggests cleaning twice a year with a composite deck cleaner.
• Above 3,100 psi: Trex says this could damage the boards and void the warranty.
• Bleach or acid: products that contain them will lighten the surface. Test a hidden spot first.

Why composite decks get dirty anyway

Trex explains that pollen and dirt left on the boards for a long time give mold something to feed on. University of Maryland Extension experts describe the same pattern on outdoor surfaces in general: algae feeds on the dust and particles that settle there (Ask Extension, 2019). Kentucky trees start pollinating as early as February and taper off in mid June (Family Allergy and Asthma), so a composite deck under trees collects a lot of it.

How we clean composite decks

Pressure is matched to the surface: wood is not treated like concrete, and wood and composite decks each get the pressure and technique that surface can handle. Before anyone cleans a composite deck, it is worth knowing which boards you have, because the right answer for a newer Trex deck is wrong for an early generation one. Tell us the brand and line if you know it when you ask for a quote.

Winter care that protects the warranty

Trex says to use a plastic shovel for snow, never a metal one, and that calcium chloride or rock salt can be used to melt ice. On early generation boards, rinse the salt off when the weather allows.