← Back to Deck Hub

How to Polish a Composite Deck

"Ultra-low maintenance" does not mean "zero maintenance." While a capped composite deck like Trex or TimberTech will never rot, warp, or require sanding, it is still an outdoor surface subjected to dirt, pollen, and barbecue grease. Here is how to keep your synthetic deck looking brand new without accidentally destroying the polymer cap.

The Golden Rule: Never Use High Pressure

The absolute fastest way to completely void a 25-year Trex warranty is to blast the boards with a 3,000 PSI pressure washer. High pressure easily slices through the protective plastic polymer cap, exposing the vulnerable wood-fiber core to water absorption and irreversible swelling.

The Fix: Only use a standard garden hose with a standard spray nozzle. If you must use a pressure washer for stubborn grime, equip it with a massive fan-tip (40 degrees or wider), hold the wand at least 15 inches away from the surface, and ensure the machine is dialed beneath 1,500 PSI.

The Soap & Water Standard (Routine Cleaning)

For routine spring cleaning, the manufacturer-approved method is remarkably simple: warm water, a squirt of grease-cutting liquid dish soap (like Dawn), and a soft-bristle nylon brush. Lightly scrub the boards in the direction of the wood grain to lift pollen and dirt out of the embossed textures, then immediately rinse clean with a hose before the soap dries.

Targeted Stain Removal

BBQ Grease & Oil: The plastic cap on composite decking will rapidly absorb hot fat from a grill. The moment grease hits the deck, immediately scrub the spot with undiluted dish soap and extremely hot water. Do not let the grease bake into the deck under the afternoon sun. Always keep a protective vinyl mat beneath your grill.

Mold & Mildew: Since modern composite boards are capped in plastic, mold cannot physically grow *inside* the board. However, it will grow on top of dirt, pollen, or spilled food that is sitting on the board. Do not use pure bleach; it will chemically degrade and fade the color tint of the deck. Use a specialized composite deck cleaner (like Corte-Clean or oxygenated bleach/OxiClean) to kill the spores globally without stripping the board's manufactured color.

Tannin Bleeding & Hard Water: Sometimes, organic liquids trapped beneath the deck (like wet leaves interacting with treated pine joists) will seep dark brown stains up between the deck boards. To neutralize tannin stains and white calcium rings from hard sprinkler water, use a dedicated composite deck brightener containing oxalic acid.