Key Takeaways -

• Regular cleaning prevents dirt buildup, mould, and stains, keeping composite decking in top condition.
• Use mild, soapy water and a soft-bristle brush and avoid harsh chemicals like bleach.
• Safe pressure washing requires a 1,500 PSI max setting and a fan tip nozzle to prevent damage.
• Composite decking needs less maintenance than traditional wood decking but still benefits from routine care.

Composite decking is strong and low-maintenance, but it still needs regular cleaning to stay in good condition. Dirt, mould, and stains can build up over time, so taking care of your deck will help it last longer and look better.

This guide will show you the best ways to clean and protect your composite decking. You’ll learn simple steps for routine cleaning, how to remove tough stains, and tips to prevent damage on the composite materials.

Keep reading to find out how to keep your composite deck looking great with minimal effort. No matter the season, a little care goes a long way in making sure your deck stays clean, safe, and durable for years to come.

General Cleaning Routine

How Often to Clean Composite Decking

Regular cleaning keeps composite decking looking fresh and prevents damage. Sweep the decking with a soft-bristled broom at least once a week to remove dirt, leaves, and debris that trap moisture.

Once a month, or whenever dirt becomes visible, rinse the deck with a garden hose on a gentle spray setting. This washes away surface grime without damaging the deck boards.

Twice a year, in spring and autumn, give your deck a deep clean. This helps remove built-up grime, mould, and stains, keeping the surface in good condition year-round.

Tools and Materials Needed

Essential Supplies

• Soft-bristled brush: for gentle scrubbing
• Warm soapy water: effective for general cleaning
• Mild dish soap (ammonia-free): safe for composite decking
• Bicarbonate of soda: helps remove tough stains
• Distilled white vinegar: useful for mould and mildew
• Garden hose: for rinsing off dirt and cleaning solutions
• Plastic shovel: for safe snow removal in winter

Optional Tools

• Pressure washer: use carefully, following manufacturer guidelines
• Composite decking cleaner: for a deeper clean when needed

Step-by-Step Cleaning Guide

Preparing Your Deck for Cleaning

Before you start cleaning, it's important to prepare your deck properly. This ensures a more effective cleaning and helps protect the surface from damage. Follow these simple steps:

1. Remove furniture, plants, and accessories. Clearing the deck gives you full access to the surface and prevents dirt from being trapped underneath.
2. Sweep away loose dirt and debris. Use a soft-bristled broom to remove leaves, dust, and other debris. This prevents grime from spreading when you scrub the deck.

Basic Cleaning Method

Regular cleaning helps maintain your composite deck’s appearance and prevents long-term damage. Follow these steps for a thorough and safe clean:

1. Prepare a cleaning solution. Mix warm water with a gentle, non-abrasive composite deck cleaner. Avoid harsh chemicals that can cause discolouration or surface damage.
2. Scrub the surface. Use a soft cloth or sponge to clean the deck, paying extra attention to high-traffic areas. Avoid abrasive materials that could scratch the composite deck boards.
3. Rinse thoroughly. Use a garden hose to remove all cleaning residue, ensuring no soap is left behind.
4. Allow the deck to dry. Let the surface dry completely before replacing furniture or accessories to prevent moisture buildup.

Using a Pressure Washer Safely

A pressure washer can be an effective way to clean composite decking, but it must be used correctly to prevent damage. Follow these steps for safe and effective use:

1. Set the pressure correctly. Keep the pressure washer at 1,500 PSI or lower to avoid damaging the deck’s surface. Too much pressure can cause scratches or strip the protective layer (1).
2. Use the right nozzle. Always attach a fan tip nozzle to distribute water evenly and prevent concentrated pressure from harming the boards.
3. Maintain a safe distance. Hold the nozzle 20-30 cm away from the deck’s surface. Getting too close can cause marks or etching.
4. Follow the wood grain. Spray along the length of the boards and follow the direction of the grain to prevent streaks or uneven cleaning, helping maintain the deck’s appearance.

Tackling Common Stains

Mould & Mildew

Moisture and debris trapped on your deck can lead to mould and mildew growth. Keeping the surface dry and free from organic matter helps prevent this issue.

To clean, use a composite deck-specific cleaner and apply it to the affected area. Scrub gently with a soft-bristle brush, making sure to reach between boards. Thoroughly rinse with clean water to eliminate any residue, then let the deck dry entirely. Regular sweeping and proper drainage will help prevent mould from returning.

Food & Grease Stains

Food spills and grease can stain composite decking if not cleaned quickly. Wipe up any spills immediately to prevent absorption into the boards. For cleaning, mix warm, soapy water with a mild dish detergent or use a degreasing agent designed for composite decks.

Scrub the area gently with a soft cloth or brush, then rinse with water to remove any residue. Prompt cleaning ensures stains don’t become permanent.

Hard Water Stains

Hard water contains minerals like lime, silica, and calcium, which can leave white stains on the deck’s surface. To remove these stains, soak a cloth in white vinegar and apply it to the affected area. Let it sit for a few minutes to break down the mineral deposits.

Rinse the deck with clean water and dry thoroughly to prevent residue buildup. Regular rinsing with fresh water can help prevent hard water stains from forming.

Oil & Grease (BBQ and Cooking Spills)

Cooking oils and BBQ grease can leave stubborn stains on composite decking. Wipe up spills as soon as possible to prevent long-term damage. Clean the area using a soft brush and mild detergent, scrubbing gently to lift the grease.

Avoid using harsh chemicals like bleach, as they can damage the deck’s surface and cause discolouration. Rinse thoroughly with water and allow the deck to dry completely.

Pollen & Leaves

Pollen and fallen leaves can create a biofilm, which encourages mould growth if left unattended. Decks near trees and plants are more prone to this issue. The best way to prevent buildup is through regular sweeping to remove debris before it settles.

Occasionally, use a pressure washer on a low setting to wash away fine dust and pollen. Keeping the deck clean reduces the risk of stains and prevents mould from forming.

Snow & Ice

Heavy snow and ice can put stress on composite decking, so safe removal is essential. Use a plastic shovel or a broom to remove snow without scratching the surface. Avoid metal shovels, as they can cause permanent damage.

For stubborn ice, apply calcium chloride to help it melt, then sweep away any remaining residue. Clearing snow regularly prevents moisture buildup and protects the deck from winter damage.

Common Mistakes to Avoid When Cleaning Composite Decking

Cleaning your composite decking the wrong way can cause damage, reduce its lifespan, and lead to costly repairs. To keep your deck in the best condition, avoid these common mistakes:

• Never use bleach or chlorine-based cleaners. These harsh chemicals can cause discolouration, weaken the material, and strip away the protective layer. Always use a gentle, composite-safe cleaner instead.
• Avoid using metal shovels or hard-bristled brushes. Metal tools and stiff bristles can scratch the surface of your decking. Use a plastic shovel and a soft-bristled brush for safe cleaning.
• Don’t exceed safe PSI when pressure washing. Using more than 1,500 PSI can damage the deck’s surface. Always use a fan tip nozzle and keep a safe distance to avoid marks and scratches.
• Leaving standing water on the deck can cause mould growth. Poor drainage or trapped moisture can lead to mould and mildew. After cleaning, ensure the deck dries completely to prevent buildup.

Frequently Asked Questions

Can I Use Vinegar to Clean Composite Decking?

Yes, vinegar can be used to clean composite decking, but it should always be diluted with water. White vinegar is effective for removing mould, mildew, and hard water stains. After applying, scrub gently with a soft-bristled brush and rinse thoroughly with clean water.

Avoid leaving vinegar on the surface for too long, as prolonged exposure may cause discolouration.

What’s the Best Cleaning Solution for Composite Decking?

The best cleaning solution for composite decking is warm, soapy water mixed with a mild, ammonia-free dish detergent. This combination is safe and effective and won’t damage the deck’s surface. For tougher stains, a composite deck-specific cleaner can be used for deeper cleaning.

Always rinse the deck thoroughly after cleaning to remove any residue.

How Do I Prevent Mould Growth on Composite Decking?

To prevent mould growth on composite decking, keep the surface clean and free from dirt, leaves, and debris. Regular sweeping and rinsing help remove organic matter that can absorb moisture and create the perfect environment for mould.

Ensuring proper drainage and airflow around the deck will also reduce moisture buildup. If mould appears, clean it promptly with a composite-safe cleaner to prevent further spread.

Can Composite Decking Be Sealed?

Sealing composite decking is generally not necessary, especially for capped composite boards, which already have a protective layer. Uncapped composite decking can be sealed, but it’s important to use a product designed for composite materials.

A sealant may help with added protection against stains and moisture, but regular cleaning is still the best way to maintain the deck’s appearance. Always follow the manufacturer’s recommendations before applying any sealant.

Are There Any Special Considerations for Cleaning Capped Composite Decking?

Yes, capped composite decking requires gentle cleaning to protect its outer shell. Use war,m soapy water and a soft-bristled brush to remove dirt without scratching the surface. Avoid harsh chemicals, bleach, or abrasive scrubbers, as they can damage the protective cap.

For tougher stains, use a composite-safe cleaner and rinse thoroughly with water.

Conclusion

Maintaining composite decking is simple, with regular cleaning and proper care. By using the right cleaning methods and avoiding harsh chemicals, you can keep your deck looking great for years.

Since composite decking is made from recycled materials, it requires less maintenance than traditional timber decking, making it a durable and eco-friendly choice. With routine sweeping, occasional deep cleaning, and preventive measures, your deck will remain clean, safe, and long-lasting in any season.

Sources -

1. https://ecoscape.co.uk/advice/how-to-clean-composite-decking/