How to Clean Composite Decking? | Soap, Water & Care

Keeping a composite deck looking new doesn’t require a pressure washer or harsh chemicals. For most boards, including Trex Transcend, Enhance, and Select lines, a bucket of warm soapy water and a soft-bristle brush is the entire routine. Trex’s official care-and-cleaning guidance says this simple method removes the dirt and debris that settles into the wood-grain embossing pattern. For tougher stains or the older generation of boards, a dedicated composite deck cleaner or a gentle pressure washer handles the job.

The Basic Cleaning Routine

Trex, the largest composite decking manufacturer, states that most of its decking needs only soap and water for regular upkeep. The process takes under an hour for an average-sized deck and requires no special equipment beyond a garden hose.

• Clear the deck. Remove furniture, planters, and loose items so every board is accessible.
• Sweep or blow off debris. Leaves, grass clippings, and dirt trapped between boards should be removed before any liquid touches the surface.
• Mix warm soapy water. A few drops of mild dish soap in a bucket of warm water is all Trex’s guidance calls for.
• Scrub with a soft-bristle brush. Work along the grain to lift dirt from the embossing pattern. A stiff wire brush or metal scraper will scratch the surface and is never recommended.
• Rinse thoroughly. A standard hose rinse removes the soap film and leaves the deck clean.

That’s the whole routine for most decks. The key is consistency — a semi-annual cleaning with soap and water prevents the buildup that turns into stubborn stains.

When You Need a Composite Deck Cleaner

If you own one of Trex’s early-generation products — Trex Accents, Trex Origins, Trex Contours, Trex Profiles, or Trex Brasilia — soap and water may not be enough. Trex’s official care instructions recommend a semi-annual cleaning with a dedicated composite deck cleaner for these older lines, which have a different cap formulation than the current Transcend, Enhance, and Select boards.

Trex’s published cleaning instructions for these products call for specific conditions. The ambient temperature should sit between 50–90°F, and the deck must be completely dry before you start. One instruction that surprises most owners: do not pre-wet or rinse the deck before applying the cleaner. Moisture dilutes the solution and makes it ineffective. After applying, let the cleaner sit for about 15 minutes, keeping it wet the whole time, then rinse thoroughly until all foaming stops. Cover or water nearby plants before and after cleaning to protect them from runoff.

When it comes to choosing a product, the market offers several tested options. Our roundup of the best cleaner for composite decks breaks down which formulas work on mildew, mold, and weather stains without damaging the cap layer. If you’re ready to buy, that guide covers the top performers.

Can You Pressure Wash Composite Decking?

Yes, but only within Trex’s published limits. Holding the wand closer, using a pinpoint nozzle, or exceeding that pressure can cut into the protective cap layer and void the warranty.

Pressure washing is best reserved for the newer high-performance lines. If you own an older product like Trex Origins or Trex Profiles, stick with the composite deck cleaner route — the softer surface materials on those boards are more easily damaged by high-pressure spray.

One more rule applies across all Trex lines: never clean a wet deck. The care-and-cleaning guidance is clear that cleaning should happen only when the deck is dry and no precipitation is expected.

FAQs

Will bleach damage composite decking?

Yes. Chlorine bleach can discolor the cap layer and break down the protective film that keeps composite boards looking new. Stick to mild dish soap for routine cleaning or a manufacturer-approved composite deck cleaner for tougher stains. Always check the care guidance for your specific product line before applying anything beyond soap and water.

How often should composite decking be cleaned?

Most manufacturers, including Trex, recommend cleaning twice a year. A spring cleaning removes winter grime, and a fall cleaning clears leaves and pollen before they stain. Decks under heavy tree cover or in humid climates may need an extra cleaning to prevent mildew growth between those semi-annual sessions.

Why is my composite deck turning black or green?

Black and green patches are almost always mildew or algae growth, common in shaded or damp areas. The fix is a composite deck cleaner designed for mildew removal, applied per the manufacturer’s instructions. If the stain is recent, it will often lift completely; old, established mildew may leave a faint shadow behind.