How To Clean Composite Decking

The best way to clean composite decking is with warm water, mild washing-up liquid and a soft-bristled brush. Sweep away loose dirt, scrub along the length of the boards and rinse thoroughly with clean water. You can also use a pressure washer, provided you follow the manufacturer’s cleaning instructions.

Although composite decking requires far less upkeep than traditional timber, it still collects dirt, algae, leaves and other deposits, particularly during the wetter months.

Fortunately, a good clean after winter and occasional attention throughout the year are usually enough to keep it looking its best. Below, we explain how to clean composite decking with or without a pressure washer, which cleaning liquids to use and how to tackle stubborn marks.

Composite Decking Cleaning Toolkit: What You’ll Need

You probably already have most of the equipment needed to clean your decking at home.

For pressure washing, wear suitable protective footwear, eye protection and clothing that keeps your skin covered. Never direct the jet towards yourself or another person, and follow the equipment manufacturer’s safety instructions.

Tip: Choose a dry, mild day for cleaning. This makes the job more comfortable and gives the decking time to dry afterwards.

What Cleaning Liquid Is Best for Composite Decking?

For everyday cleaning, mild washing-up liquid diluted in warm water is usually sufficient. An ammonia-free washing-up liquid is a sensible starting point, as it helps loosen surface dirt and grime without requiring stronger cleaning chemicals.

You can also use a suitable all-purpose cleaner. Ecoscape’s published decking care guidance recommends an all-purpose cleaner and water with a scrubbing brush as one of its cleaning methods.

For heavier dirt or algae, choose a cleaner specifically approved for your composite decking range. Avoid using household bleach, strong acids or concentrated patio-cleaning products unless the decking manufacturer confirms they’re suitable.

How to Clean Composite Decking Without a Pressure Washer

For most gardens, this straightforward four-step method is all you’ll need.

Step 1: Clear and sweep the decking

Move garden furniture, plant pots and other accessories out of the way.

Sweep the entire surface with a soft-bristled broom, removing leaves, loose soil and accumulated dirt. Pay particular attention to the gaps between boards. Keeping these clear helps rainwater drain away and allows ventilation beneath the decking. Avoid using sharp metal tools to remove trapped debris.

Step 2: Prepare your cleaning solution

Fill a bucket with warm water and add a small amount of mild washing-up liquid. Lightly wet the decking first to help loosen surface dirt. You don’t need a particularly strong cleaning mixture. A small amount of detergent should be enough for general cleaning.

Step 3: Scrub along the boards

Dip your soft-bristled brush into the soapy water and gently scrub along the length of the decking boards.

Pay attention to textured areas and places beneath furniture or plant pots where grime can accumulate. For stubborn dirt, allow the soapy water a little time to loosen the deposits before brushing again. Work in manageable sections so the detergent doesn’t dry on the surface.

Step 4: Rinse thoroughly

Using a hose or clean water, rinse away the dirt and remaining detergent. Make sure no soapy residue is left behind, particularly in textured areas or between boards. Allow the decking to dry before replacing furniture.

For most composite decking, that’s all that’s needed to restore a clean, fresh-looking surface.

Can You Clean Composite Decking With a Pressure Washer?

Yes. Ecoscape composite decking can be pressure washed when you follow the correct technique and the guidance for your particular decking range.

Pressure washing can be particularly useful for larger areas or decking that has accumulated dirt over winter. Ecoscape’s installation guide recommends using a fan-shaped spray, keeping the nozzle at least 20cm from the surface and directing the water along the length of the boards.

To pressure wash composite decking:

• Sweep away loose dirt, leaves and debris.
• Fit a wide, fan-shaped spray nozzle.
• Keep the nozzle at least 20cm from the decking surface.
• Wash along the length of each board, keeping the spray moving.
• Avoid concentrating high-pressure water on one area.
• Rinse thoroughly and allow the decking to dry.
• Use a pressure setting suitable for your decking product, and never assume that the highest setting on your machine is appropriate.
• Wear safety glasses, waterproof clothing and suitable protective footwear to guard against spray and debris. Keep other people and pets away from the area while cleaning.

Important: Excessive water pressure or a concentrated jet can damage the decking surface. Always follow the care instructions for your product and pressure washer. You can find more information in the Ecoscape Composite Decking Installation Guide.

How to Deep Clean Composite Decking

After a wet winter or a long period without cleaning, your decking may need more than a quick wash.  Dirt, pollen, algae and other deposits can build up on the surface, leaving it looking dull or discoloured.

For a deeper clean:

• Remove furniture and thoroughly sweep the boards.
• Clear trapped leaves and debris from the drainage gaps.
• Apply a composite-compatible cleaning solution according to its instructions.
• Allow the recommended contact time without letting the solution dry on the decking.
• Gently scrub stubborn areas, or use an approved pressure-washing method.
• Rinse thoroughly with clean water.
• Test unfamiliar cleaning products on a small, inconspicuous area first.

For most UK gardens, a thorough clean in spring will remove much of the dirt and organic material that accumulates during autumn and winter.

How to Remove Algae, White Marks and Stains From Composite Decking

Composite decking is designed for outdoor conditions, but its surface can still collect biological growth and everyday stains. The appropriate cleaning method depends on what’s causing the marks.

Green algae and white surface deposits

Algae commonly develops on outdoor surfaces in damp, shaded conditions, particularly where dirt and moisture accumulate.

Biological growth can sometimes appear as pale or whitish deposits rather than the familiar green film. However, not every white mark is algae; mineral deposits and dried cleaning residue can look similar.

Start by washing the affected area with warm soapy water and a soft brush. For persistent algae, use a composite-compatible cleaner approved for biological growth, following its instructions.

Keeping decking gaps clear and removing fallen leaves will help reduce the conditions that encourage algae to return.

White spots caused by hard water

White or chalky marks that appear after water evaporates may be mineral deposits.

Try washing the affected area with clean water and a soft cloth. If the marks remain, use a manufacturer-approved cleaner suitable for removing mineral residue. White vinegar is sometimes recommended for hard-water marks, but its suitability depends on the decking material and finish.

Oil and grease stains

Barbecues and outdoor dining can occasionally leave oily marks.

Blot up excess oil or grease promptly, then clean the affected area with warm soapy water and a soft brush. Rinse thoroughly. For stubborn marks, check the manufacturer’s recommended cleaning products.

Food, drink and bird droppings

Most everyday spills and marks can be removed with mild washing-up liquid and warm water. Remove any solid material carefully, wash the affected area and rinse thoroughly.

Cleaning spills promptly helps prevent more stubborn staining.

Can You Use Vinegar to Clean Composite Decking?

White vinegar is sometimes recommended for cleaning composite decking, particularly for hard-water deposits and certain surface marks.

However, it isn’t necessarily suitable for every composite decking product.

Some manufacturers permit diluted white vinegar for specific cleaning tasks, while others recommend avoiding acidic cleaning products.

Before using vinegar:

• Check your decking manufacturer’s recommendations.
• Only use an approved dilution and application method.
• Test a small, inconspicuous area first.
• Never mix vinegar with bleach or other cleaning chemicals.
• Rinse thoroughly after cleaning.

For general dirt, warm soapy water is usually the simpler choice. For algae or stubborn deposits, use a cleaner approved for your decking rather than relying on homemade chemical mixtures.

What Should You Avoid When Cleaning Composite Decking?

Using unsuitable tools or cleaning products can damage the finish of composite decking.

In particular, avoid household bleach, strong acids and concentrated patio cleaners (unless the manufacturer confirms they are suitable), wire brushes and other abrasive tools that can scratch the surface, and excessive pressure or a concentrated jet when pressure washing.

Always check the care instructions for your particular decking range before using an unfamiliar cleaning method.

How Often Should You Clean Composite Decking?

For most UK gardens, cleaning composite decking once or twice a year is generally sufficient, alongside occasional sweeping and attention to spills.

Ecoscape’s official care guidance recommends cleaning once or twice annually to remove accumulated dirt and debris.

A simple routine is to:

• Spring: Give the decking a thorough clean after winter.
• Summer: Sweep occasionally and clean food or drink spills promptly.
• Autumn: Remove fallen leaves and keep drainage gaps clear.
• Winter: Clear excessive debris and avoid allowing slippery deposits to accumulate.
• Decking beneath trees or in damp, shaded gardens may need cleaning more frequently.
• Unlike traditional timber, composite decking doesn’t require regular sanding, staining, painting or sealing as part of its normal upkeep.

For more information about the difference between low maintenance and no maintenance, read our guide to whether maintenance-free decking really exists.

Frequently Asked Questions

Can you use Fairy Liquid to clean composite decking?

Yes, mild Fairy Liquid or a similar washing-up liquid diluted in warm water is generally suitable for everyday cleaning, provided the formulation is compatible with your decking. Rinse thoroughly afterwards.

Can you use a Kärcher pressure washer on composite decking?

Yes, a Kärcher or similar pressure washer can be used if the settings and technique comply with the decking manufacturer’s instructions. Use a fan-shaped spray, maintain the recommended distance and avoid concentrating the jet on one area.

Can you use patio cleaner on composite decking?

Not every patio cleaner is suitable. Some contain bleach, acids or other chemicals that may affect composite surfaces. Choose a cleaner specifically approved for your decking product.

How do you clean slippery composite decking?

Slipperiness may be caused by algae, dirt or other deposits collecting on the surface.

Sweep away loose debris, wash with warm soapy water and gently scrub the affected areas. Rinse thoroughly and allow the surface to dry.

Persistent biological growth may require an approved composite decking cleaner.

Does composite decking need sealing after cleaning?

No. Ecoscape composite decking doesn’t require routine sealing, staining or painting. Once the surface has been cleaned and rinsed, simply allow it to dry.

Keeping Your Composite Decking Looking Its Best

Cleaning composite decking doesn’t have to be complicated or time-consuming.

For everyday dirt, warm soapy water and a soft brush are usually enough. A pressure washer can also be useful for larger areas or a deeper clean, provided it’s used correctly.

The most important things are to choose suitable cleaning products, keep drainage gaps clear and remove algae or other surface deposits before they become difficult to shift.

With an occasional clean and a little attention after winter, your composite decking can continue looking its best throughout the year.

At Ecoscape, we design our composite decking to be low maintenance from the start, so caring for it stays this simple. Explore our composite decking range to see the finishes available, order a free sample pack, or get in touch if you have a question about caring for your boards.