How to Clean Composite Decking

Decking & Cladding
How to Clean Composite Decking

One of the main advantages of composite decking is its unrivalled longevity. Unlike timber decking, your decking won’t rot or warp. Plus, you needn’t worry about applying treatments or giving it a lick of paint each year. But to ensure you get the most from your composite decking, you’ll still need to show it some TLC.

Thankfully, all it takes is an annual deep clean to keep your composite decking in top-notch condition. It will also make your decking more attractive and safer to walk on throughout the year. But exactly how do you clean composite decking and what equipment will you need to? In this article, we’ll answer those questions and more!  

Common Issues for Composite Decking

Although tougher than its timber alternative, composite decking remains susceptible to issues such as algae build-up, moss growth and more. If you spot any of these, you’ll need to tackle them as quickly as possible. Here’s what to keep an eye out for:


If your decking is often wet from rain or dew, then you’re likely to face the challenge of algae. Much like it would on timber decking, algae can ‘eat away’ at composite decking over time. As well as impacting the longevity of your decking, algae can make it slippy and more hazardous to walk on.


Moss thrives in moist yet mild conditions, such as a spring morning. So, it is common to find moss growing throughout your decking and particularly in the areas less prone to traffic. But as mosses hold in moisture, they can cause similar damage as algae in a surprisingly short timeframe.

Water Stains

Many decks have areas where water will naturally rest, whether that’s due to a ‘dip’ in the structure or where furniture stops its flow. Assuming this water can evaporate regularly, this shouldn’t cause issues beyond potentially unsightly water stains.

How to Clean Your Composite Decking

Now that you know what to keep an eye out for, let’s focus on getting your decking clean. Thankfully, keeping your composite decking spotless is far easier than timber decking. There is no need to sanding, treating, repainting etc! Here are the four steps you’ll need to follow:

1.     Clear any leaves, dirt, or debris

To begin, you’ll need to remove any loose leaves, dirt, or other debris. Whilst you can buy brushes purposely made for cleaning your decking, virtually any soft-bristle brush will work. Avoid using a hard-bristle brush as it may scratch your decking or even damage its outer coating.

2.     Prepare a recommended cleaner

To have the best chance of removing tough dirt, algae, mildew, and grease; you’ll benefit from using a specially designed cleaner. There are a few options available, such as the Rustins Composite Decking Cleaner, but always seek the manufacturers recommendation.

If you don’t have a composite decking cleaner, then don’t worry. You’ll be able to clean most dirt off with an ammonia-free dish washing liquid that’s been mixed with warm water. Alternatively, you can use apple cider vinegar that’s also been diluted with warm water. Again, seek the manufacturers recommendations beforehand.

3.     Deep clean your decking

With your decking cleaner and soft-bristled brush to hand, you can begin cleaning your composite decking. Whilst applying a little downward pressure, you should ‘scrub’ in the direction of the grain. Then repeat the same against the grain to ensure that there is no dirt and debris left behind.

There will be some areas of your decking that are more prone to getting grubby. This could include any steps as well as areas surrounding furniture. You may need to go over these areas a few times to ensure that they’re free of dirt and debris.

4.     Rinse to finish

With the most tiring part behind you, it’s time to rinse your composite decking. If possible, use a hosepipe to push any residue off the sides of your decking. But if you don’t have a hosepipe, then simply use a few buckets of water.

For the perfect finish, soak up any standing water with a sponge or towel to avoid spots of residue from your cleaner. Then simply allow your decking to air dry before returning any furniture to ensure you don’t end up with moisture resting beneath.  

More Questions About Cleaning Your Decking

Whilst these steps should answer your big questions, you may have more questions about getting your decking shipshape. From what equipment you can use to how often you’ll need to clean, here are a few common questions and answers:  

Can You Use a Power Washer?

Yes, you can safely use a power washer to clean your composite decking if it has a PSI no greater than 3100 psi. It is, however, not recommended to use a power washer with uncapped composite decking. This is as they are usually softer and, therefore, a power washer could damage your boards.

Which Cleaner Should You Use?

Aim to use a decking cleaner that’s free of harsh chemicals such as bleach to prevent any damage or discoloration. If you don’t have a specially formulated decking cleaner to hand, you can use ammonia-free dish washing liquid combined with warm water.

How Often Should I Clean My Decking?

You should give your composite decking a deep clean at least once a year, ideally after winter. To minimise any damage to your decking throughout the year, try to regularly clear dirt and debris with a quick brush.  

What If My Decking Boards Are Damaged?

If your decking boards are structurally damaged, then these should be replaced. Cleaning damaged boards could worsen the damage and will almost certainly result in water finding its way into the core of your decking.

What If My Subframe is Damaged?

Your subframe acts as the foundations of your decking. So, any issue here could prove catastrophic for your entire decking. If your subframe has any degradation, such as rot, then this should be tackled as soon as possible. Read our guide to building a decking subframe.


There you have it – everything you need to know about cleaning composite decking! By following the tips in this article, you’ll be able to enjoy your deck for many years to come. But if you’re yet to lay a deck in your garden, here are a few decking ideas as well as a handy guide to fitting decking.

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