How to Clean Composite Decking

Composite decking is durable, stylish, and low-maintenance. But even the best boards need cleaning from time to time. Dirt, leaves, mold, and spills can make your deck look worn out. Ignoring routine care shortens the lifespan of your deck boards. Knowing how to clean composite decking properly will help keep it looking new. This guide breaks down each step, providing clear, straightforward advice that anyone can follow.

Clear the Deck

Start with the basics. Clear everything off the deck. That means furniture, grills, flowerpots, or any items that could block cleaning.

Small pebbles or trapped debris under furniture legs can scratch the boards. Don’t skip this part, even if you’re in a hurry.

Once the surface is open and empty, you’re ready to begin your cleanup.

Remove Debris

Before you wash anything, sweep the deck thoroughly. Use a stiff-bristled broom to remove loose dirt and surface debris.

Don't forget between the gaps of deck boards. Trapped leaves and seeds can lead to staining and even mold growth.

If your deck is covered in pine needles or stubborn particles, consider using a shop vacuum.

You want to start with a clean surface before applying any solution.

Prepare the Cleaner

Choose your cleaning solution carefully. You can use a store-bought composite deck cleaner or make your own.

For mild stains, a vinegar solution or dish soap mixed with water works fine. For tougher grime or mold, use sodium hypochlorite or sodium percarbonate cleaners.

Avoid harsh chemicals like acetone or bleach, which can damage composite materials.

Always follow product directions, and wear gloves if using chemical cleaners.

Section Off the Deck

Divide the deck into small sections for easier cleaning. Why? Because it’s easier to control rinsing and prevent cleaner from drying too fast.

Pick one corner and work methodically across the space. This helps ensure you clean evenly and avoid streaks.

Don’t rush the process. Spending extra time on each section gives you better results in the end.

Clean and Rinse The Composite Deck

Use the right tools and methods

Start scrubbing using a soft deck brush or a long-handled broom. Make sure the brush is non-metallic to prevent scratching the surface.

Work the cleaner into the boards. Scrub along the grain of the decking to get the best results. If you're using a power washer, keep the pressure under 3100 PSI and use a fan tip nozzle.

Hold the washer at least 8 inches above the surface. Stay consistent. Don’t blast water too close or you risk damaging the deck finish.

Once scrubbed, rinse thoroughly with clean water. Leftover cleaner can create residue or attract more dirt.

Don't forget corners, gaps, and under railings.

Dry the Deck

Let the deck dry naturally after cleaning. Choose a warm, sunny day if possible. Wind helps speed up the process.

Avoid walking on the surface while it’s still wet. Foot traffic may leave prints or kick up dirt again.

If rain is expected, plan your cleaning for another day. Wet boards attract dirt easily if not dried properly.

A dry deck is safer and looks better.

Best Cleaner for Composite Decking by Problem Type

Not all messes are created equal

Different stains need different cleaners. One solution won’t fix everything.

For mold or mildew, use a cleaner with sodium hypochlorite or one labeled for mold removal. Mold Armor or Olympic® Premium Deck Cleaner are strong options.

If you're battling grease or food stains, try a degreasing agent mixed with warm water.

For rust stains, use a product with oxalic acid or make a baking soda paste. Rub gently and rinse thoroughly.

Sap or tree gunk? Use isopropyl alcohol on a rag, then rinse with soap and water. Always test on a small spot first.

Avoid cleaners with ammonia. They damage Trex® and other composite deck brands.

Some brands like Corte Clean work for multiple problems. Read the label to match your issue.

Common Cleaning Challenges

Dealing with recurring messes

Composite decks are tough, but not bulletproof. The most common problems include black mold spots, dirt buildup, or hard water stains.

Black mold loves shady, damp areas. If you see it returning fast, check your drainage. Keep gutters clear and trim nearby plants.

Surface dirt often comes from shoes or wind. A quick rinse with a hose weekly helps reduce buildup.

Hard water stains leave white marks. Use a 50/50 vinegar and water solution. Spray, let it sit, then rinse.

If snow falls in your area, avoid salt rocks. Use calcium chloride products that are deck-safe instead.

Don’t forget to clean under furniture and around planters too. Hidden dirt can cause long-term discoloration.

Personal Tip: When I Cleaned My First Composite Deck

Years ago, I cleaned my first composite deck with nothing but dish soap and a stiff broom. It looked fine at first. But within days, the mold returned—worse than before.

What did I learn? Use the right cleaner for the job. A generic cleaner can’t remove deep-set mold or oil. Now I always check the stain type before picking a solution.

This small change made a big difference in how long the deck stayed clean.

Conclusion

Knowing how to clean composite decking isn't complicated. But it does require the right tools, cleaner, and a bit of care.

Start by clearing the deck, removing debris, and picking the best cleaner for your problem. Work in sections, rinse completely, and let it dry fully.

By doing this once or twice a year, you’ll protect your deck from wear and stains. It’ll also look great for years.

Don’t wait until the deck looks filthy. A little routine effort saves money and time down the road.

Also Read: Benefits of Premium Landscape Maintenance Services