How to clean composite decking - a step-by-step guide

Get your composite decking looking like new with our easy how-to

composite decking in outdoor space with tall green plants, a deck chair, festoon lights and candles
(Image credit: Lights4Fun)

One of the great things about composite decking is the promise of a lower-maintenance, easy to clean deck that won't require regular scrubbing. But, learning how to clean composite decking should still be part of your essential summer prep checklist, so that you can keep your composite decking ideas looking as good as new.

Learning how to clean composite decking is a bit of a different process to cleaning wooden decking. Composite is a delicate material that won't react well to harsh chemicals or abrasive scrubbers, which is why it's important to exercise a little more care and learn how to do the job properly.

'Cleaning composite is a good way to keep it looking as good as new, and ensure it lasts as long as possible,' says Allan Jeffrey, Managing Director, Ultra Decking. 'Clearing away debris not only makes your composite decking look better, but it can also improve safety by making it less slippery.'

And while composite is a long-lasting and durable material, regular cleaning and maintenance will ensure its longevity, so you won't need to rethink your garden decking ideas any time soon. Our step-by-step guide will show you how to clean composite decking thoroughly, without causing any damage.

How to clean composite decking

‘Composite decking is less likely to stain compared to traditional decking,’ says Allan. ‘It doesn’t need regular treating, staining, or painting either. Composite decking is manufactured from HDPE plastics and wood fibres to create hard-wearing decking boards.'

So although your composite decking will require less maintenance than other types, you still can't skip cleaning altogether. 'Cleaning composite decking is an important part of its maintenance and care. As it is made from a combination of plastic and wood fibres, it is susceptible to mould and mildew growth if it’s not properly cleaned,' says Nick Whiley, International Project Director, Trekker Global. 'These organisms thrive in damp discolouration, staining, and even structural damage to the decking.'

So that you can avoid mould and mildew from finding a permanent home on your deck, we've asked the experts to share their top tips on how to clean composite decking.

Grey composite decking with outdoor corner sofa

(Image credit: NeoTimber)
Headshot of Allan Jeffrey, composite decking expert
Allan Jeffrey

Allan Jeffrey is the founder of Ultra Decking. He has years of experience in the design, development, and fabrication of advanced new composite materials and expertise covering composite decking and garden design.

What you'll need


1. Get prepped for cleaning

First, remove garden furniture, pots, planters, doormats, and the barbecue. Then sweep your composite deck with a soft-bristled brush to remove loose debris, such as grass cuttings, fallen leaves and twigs, trying to get in the gaps as much as possible.

If needed, use a scraper or putty knife, available at Brewers, to remove any dirt that’s trapped between the boards. Just be careful not to scratch the surface of the composite. You can also spray the area with a hose to remove debris, but use a gentle pressure.

composite decking in outdoor area with lots of green plants

(Image credit: Ultra Decking)

2. Clean any railings

If you have railings around your deck, then start by washing them down with soapy water and a decking cleaning hand brush. Then, hose it off, removing any debris and cobwebs. Deck railing ideas can really help create that sense of an outdoor room.

To clean the composite boards, mix up a bucket of warm soapy water and use a brush to get into the embossed pattern of your boards. 

You can also buy oxygenated cleaners, such as Oxylyse, available at Amazon, but never use household bleach as you can discolour the boards.

Osmo Decking Cleaning Scrub Brush (150mm) | £18.99 at Amazon

Osmo Decking Cleaning Scrub Brush (150mm) | £18.99 at Amazon

A brush designed specifically for cleaning decking, the soft bristles are ideal for removing debris from the composite without damaging it. 

3. Wash the decking with soapy water

Brush cleaning decking

(Image credit: NeoTimber)

Working in a small section at a time – about 5-metre sections to prevent any cleaner from drying out and possibly leaving a film on the deck – wash the composite decking with the soapy water and the brush. Then rinse clean and allow to dry, before replacing your garden furniture and any pots moved.

If you have any stubborn planter or pot marks, then try giving more of a scrub, or using oxygenated cleaner and water to remove them.

4. Clean little and often

Rinsing off a composite deck periodically throughout the year will prevent the build-up of dirt, mildew, and grime. Spot stains – such as grease or spilt drinks – should be cleaned off affected boards with soapy water and left to ‘weather’ for a month or so to regain their original colour.

composite decking in outdoor with tall green plants and a deck chair and candles

(Image credit: Lights4Fun)
Rustins Composite Decking Cleaner 4L - £11.40 at Amazon

Rustins Composite Decking Cleaner 4L - £11.40 at Amazon

If you want to get your composite decking looking like new again, investing in a specially formulated product like this one from Rustins will do the job perfectly. It effectively removes dirt, moss, grease and stains, without damaging the composite.

5. Power wash for a deeper clean

Grey decking being cleaned with power washer

(Image credit: NeoTimber)

Power washers are great for learning how to clean composite decking in need of a deeper, more thorough clean. 'You can use a pressure washer machine if the water pressure does not exceed 6 bar and is done from a good distance,' says Nick from Trekker Global.

Use a pressure washer like the Mac Allister Corded Pressure Washer 1.8kW, available at B&Q if any stubborn stains are still showing on your decking, and the power of the machine should help to lift them away.

What should you not use on a composite deck?

When learning how to clean composite decking, it's important to avoid anything too harsh or abrasive. Bleach and other strong cleaning chemicals, as well as rough and coarse tools have the potential to damage the composite, which would ruin the look of your decking. 

'When cleaning composite decking, it’s important to avoid using certain cleaning products or methods that can potentially damage the decking material,' says Nick Whiley. 'Bleach or chlorine-based cleaners will discolour or fade the decking, and we would also recommend avoiding using any abrasive scrubbers or brushes as this is likely to scratch the surface.’  

'You should not clean composite decking with a coarse wire brush or broom, as this could damage the surface of the board,' Lewis Darley, Content Creator at NeoTimber expands. 'Instead, before washing, use a soft bristled brush to sweep away debris, going in the direction of the grain and not against it.'

Grey composite decking area in garden with corner sofa and egg chair

(Image credit: NeoTimber)

Can I clean composite decking with washing up liquid?

Washing up liquid will clean composite decking without damaging the surface, and as it's something you probably already have in the house, it's a great option to use.  

'Usually, a mild detergent solution such as washing up liquid is the recommended cleaning solution for composite decking,' says Nick. 'It’s good for gently removing dirt, grime, and any other types of debris from the surface.'

'Paired with a soft brush, washing up liquid, or other gentle cleaners such as diluted vinegar, make a great way to clean decking,' agrees Allan from Ultra Decking. 'Make sure to rinse afterwards, to reduce the chance of build up.'

Can I jet-wash composite decking?

Can I jet-wash composite decking?

‘Many homeowners use a power washer to clean their decking because it’s faster, but when using one on composite decking, you need to be very careful. You should not apply too much pressure when using the machine,’ says Allan.

‘Composite decking is not like a wood deck; while pressure washing your deck, the fan can damage its surface if you move the pressure washer too close to it. 'A water hose is a safe and good option if you want to rinse the surface of a composite deck.’

If you do decide to jet your composite deck, then use a fan tip nozzle and the washer’s lowest setting (no more than 1500psi). Spray in the direction of the board and keep the nozzle at least 20cm from the board.

Is vinegar a good composite deck cleaner?

Cleaning with white vinegar is another great option for composite decking. It will decompose any mould or mildew that has built up, without damaging the deck's surface.

‘Vinegar is great for removing mould on composite decking,’ says Allan. ‘Mix a half cup of white vinegar with a gallon of water. Then use the mixture to scrub the decking.’

Alternatively, you can use baking soda, which is another powerfully active but natural cleaning agent. ‘Sprinkle some on the decking then scrub with a soft bristle brush. Then rinse with clean water.’

Now you know how to clean composite decking, you can reap the rewards of your hard work all summer long!

Jennifer Morgan

Jennifer Morgan is an award-winning editor, writer and stylist, with over 25 years’ experience writing, styling and editing home interest magazines. Jennifer was the deputy editor of Ideal Home from 2008-2010, before launching Ideal Home’s sister title, Style at Home in 2010. Jennifer went on to launch several craft magazines and websites, before going freelance in 2016, with a client list that includes John Lewis, Dunlem and Nordic House. Today, she writes for Ideal Home, Real Homes, Waitrose, Woman & Home, Sainsbury’s Magazine and Homes & Gardens. But it was during lockdown that Jennifer realised her dream of publishing her own magazine – Simply Scandi.

With contributions from