Cleaning Composite Decking: Do's and Don'ts

The Composite Decking Misconception

When you invested in composite decking for your Jacksonville home, you probably heard "low maintenance" more than a few times. And compared to wood, it is — no annual sealing, no staining, no splinters.

But "low maintenance" doesn't mean "no maintenance," and using the wrong cleaning methods can void your warranty, damage the surface, and create problems that are expensive to fix. At Clean Fix Jax, we clean composite decks throughout Northeast Florida, and we've seen every type of damage caused by improper cleaning.

Here's the definitive guide to what you should and shouldn't do.

Understanding Composite Decking

What It's Made Of

Composite decking is a blend of wood fibers (or rice hulls in some products) and plastic resins (typically polyethylene or PVC). The wood component makes up 30-50% of the material, which means composite decking is not impervious to moisture, mold, and organic growth — it's just more resistant than wood.

In Jacksonville's humidity, the wood fibers in composite decking can absorb moisture, creating conditions for mold growth at the surface. The plastic component provides durability and stain resistance, but it can be damaged by certain chemicals and high heat.

Warranty Considerations

Major manufacturers like Trex, TimberTech, and Fiberon have specific cleaning requirements in their warranty terms. Using unapproved cleaners or methods can void your warranty. Trex explicitly prohibits pressure washing above 1,500 PSI and the use of chlorine bleach.

TimberTech prohibits power washing entirely. Always check your manufacturer's care guidelines before cleaning — a 5-minute internet search can save you from voiding a 25-year warranty.

The Do's of Composite Deck Cleaning

Do: Clean Regularly

Sweep your deck weekly and wash it with soap and water monthly during the humid season (April through October in Jacksonville). Regular cleaning prevents the buildup of pollen, dirt, and organic matter that feeds mold growth. A simple rinse with a garden hose after each use removes fresh debris before it can settle.

Do: Use Manufacturer-Approved Cleaners

Most manufacturers recommend a mild dish soap and warm water solution for routine cleaning. For tougher stains, manufacturers typically approve specific composite deck cleaners — Trex recommends their own DeckCleaner, while TimberTech approves DeckMax and other specific brands.

These products are formulated to clean without damaging the composite material or voiding the warranty.

Do: Address Mold Promptly

In Jacksonville, mold on composite decking appears as black spots or a gray-green film, typically in areas with poor drainage, heavy shade, or accumulated debris. Use a composite-approved mold remover — most contain sodium percarbonate (oxygen bleach) rather than chlorine bleach.

Apply, let sit for 15-20 minutes, scrub with a soft-bristle brush, and rinse thoroughly. Treat mold as soon as you see it — established mold colonies penetrate the surface texture and become increasingly difficult to remove.

Do: Clean Between the Boards

Debris accumulation between composite deck boards blocks drainage and promotes mold growth on the board edges and underneath. Use a putty knife or specialized deck gap tool ($10-15) to clear debris from between the boards at least twice per year — more frequently if your deck is under trees in Orange Park or St. Augustine.

The Don'ts of Composite Deck Cleaning

Don't: Use Chlorine Bleach

Chlorine bleach (sodium hypochlorite) breaks down the wood fibers in composite decking, causing fading, surface deterioration, and structural weakening over time. It also voids most manufacturer warranties.

If you've been told to use bleach on your composite deck, stop — it's outdated advice that causes real damage. Use oxygen bleach (sodium percarbonate) instead, which cleans without damaging the composite material.

Don't: Pressure Wash at High Pressure

Pressure above 1,500 PSI can etch the composite surface, creating a rough texture that attracts dirt and is impossible to smooth. If you must use a pressure washer, use the widest fan tip (40-degree), maintain at least 12 inches of distance from the surface, and never use a 0-degree tip.

At Clean Fix Jax, we prefer to soft wash composite decks — applying cleaning solution with a pump sprayer and rinsing with garden-hose pressure. This method is safe, effective, and warranty-compliant.

Don't: Use Metal Brushes or Abrasive Pads

Wire brushes and abrasive scouring pads scratch the composite surface, creating permanent damage that collects dirt and stains. Use only soft-bristle brushes — a deck brush with nylon or polypropylene bristles is ideal. For stubborn stains, increase the cleaning solution concentration rather than the scrubbing aggressiveness.

Don't: Leave Standing Water

While composite decking is more water-resistant than wood, standing water promotes mold growth and can seep into the wood fiber component. Ensure your deck has proper drainage (at least 1/8 inch of slope per foot) and clear any areas where water consistently pools.

Tough Stain Removal for Composite Decks

• Oil and grease: Apply a composite deck cleaner immediately. For set-in oil, try Dawn dish soap applied directly, let sit 15 minutes, scrub, and rinse
• Rust stains: Use a rust remover specifically formulated for composite decking — standard rust removers can discolor the surface
• Food and drink: Most food stains come up with dish soap and warm water. Barbecue sauce and wine may require a specialized composite cleaner
• Berry and leaf stains: A 50/50 white vinegar and water solution applied for 20 minutes usually removes tannin stains from leaves and berries

At Clean Fix Jax, our exterior cleaning service includes warranty-safe composite deck cleaning. We serve Jacksonville and all of Northeast Florida. Contact us for a free estimate.

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