How to Clean Composite Decking in 7 Simple Steps (2025)

Your composite deck looked pristine when installed, but now it’s covered in dirt, mildew, and stains. Unlike wood, composite materials resist rot—but they still need proper cleaning to maintain their appearance and longevity. Using harsh chemicals or pressure washers can damage the surface, leaving you frustrated with faded or warped boards.

The right composite decking cleaning method can restore your outdoor space without causing harm. In this guide, we’ll cover the safest techniques, recommended tools, and expert tips to keep your deck looking new. For stubborn stains, consider a deck-specific cleaner or mild soap solution.

Key Takeaways

• Avoid pressure washing—it can strip the protective layer and cause splintering.
• Use soft brushes to prevent surface scratches.
• Clean seasonally to prevent deep-set grime.
• Spot-test cleaners to ensure no discoloration occurs.

1. Clear the Deck Surface

Remove furniture, planters, and debris before cleaning. Sweep with a soft-bristle broom to eliminate loose dirt and leaves. Pay attention to gaps between boards where mold thrives. Cover nearby plants if using a cleaning solution to prevent chemical exposure.

2. Choose the Right Cleaner

Use mild soap, water, and a soft brush; avoid harsh chemicals or pressure washing. Opt for:

• Dish soap + warm water (gentle for routine cleaning)
• Vinegar solution (1:1 water and vinegar for mildew)
• Oxygen bleach (safer than chlorine bleach for stains)

Avoid bleach-based or acidic cleaners—they can degrade composite materials.

3. Scrub Gently with the Grain

Work in small sections using a nylon brush or sponge mop. Apply cleaner, let it sit for 5–10 minutes (don’t let it dry), then scrub lightly along the board’s texture. Rinse immediately with a garden hose.

4. Tackle Stubborn Stains

For grease or rust:

• Baking soda paste (apply, scrub, rinse)
• Rubbing alcohol (for ink or dye stains)

Always spot-test first.

5. Rinse Thoroughly

Use low-pressure water to remove residue. Leftover soap attracts dirt, leading to faster discoloration.

6. Dry the Deck

Prevent water spots by squeegeeing or air-drying. Avoid walking on wet boards to reduce slip hazards.

7. Apply a Protective Coating (Optional)

Some composite decks benefit from a UV-resistant sealant. Check manufacturer guidelines before application.

Cleaning Solutions Comparison

For more tips on outdoor cleaning, explore our guide on vinyl siding maintenance.

Final Thoughts

Regular cleaning preserves your composite deck’s color and texture. Stick to gentle methods, and consult your manufacturer’s care instructions. With minimal effort, your deck will stay beautiful for years.