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How to Clean Composite Decking: Step by Step

24 January 2024

Your composite decking can last over 20 years if it’s maintained and cleaned properly – and the good news is you only need to clean it once or twice a year for it to stay looking fresh. Composite decking offers many advantages over timber decking, and low maintenance is definitely one of them.

With this in mind, we’ve put together a handy guide on the best way to clean composite decking. 

What will you need? 

You don't need tons of expensive supplies to clean composite decking – chances are you’ll have everything on the list below already in your home:

  • A brush with soft bristles
  • Warm water in a bucket
  • A hose pipe
  • A sponge
  • Washing up liquid 

It’s important to use a soft bristle brush instead of a medium or hard one which can scratch the surface of the deck. It’s also best to clean on a sunny day without the rain or wind forcing you inside. 

Note: Avoid using any strong or harsh chemicals as they can discolour or damage the deck.

Clean your composite decking: step by step

Step 1: Remove any furniture 

Start by removing any items from the deck including furniture, plant pots, or mats. This will help to ensure the whole desk is cleaned, with no patches left by the end.

Step 2: sweep away any debris 

It’s important to remove any dirt, leaves or debris from the deck before you add water. You can sweep it away using a dustpan and brush, or even a car vacuum cleaner for any fine pieces of soil that may have accumulated. 

Step 3: rinse the deck

Using your bucket of warm water or hose, rinse the deck ensuring that it’s completely soaked. This will make the cleaning process easier and allow you to effectively remove any stains. 

Step 4: mix your solution and clean the deck

The next step is to mix a cleaning solution of warm water with a few drops of washing up liquid. Apply the solution to your composite decking and then, using your soft bristle brush, gently scrub the deck along the length of the board. You can use a smaller brush to get into the gaps. 

You should pay extra attention to any dirt or stains, and use a sponge to get into any nooks or corners. If your deck is large, it’s best to work in sections so that you don’t miss any spots and to avoid the solution drying before you get to it. 

Note: Add extra water to the deck if it dries mid-clean. 

Step 5: the final rinse

After you are done scrubbing, rinse the deck with warm water using your bucket or hose. Be sure to remove all of the solution so that it doesn’t stain or leave behind any residue. 

How to clean your composite decking: FAQs

Can you use bleach to clean composite decking? 

You should avoid using harsh chemicals, especially bleach, when cleaning your composite decking. It contains sodium hypochlorite which can cause irreversible damage to your deck including staining, discolouration, chips or cracks. 

Washing up liquid mixed with warm water works perfectly well and isn’t harmful to the material. If you find that you need something stronger to remove stains, you can search for a compatible cleaning solution that’s recommended by the manufacturer.

Should you use a pressure washer to clean composite decking? 

Your composite decking can be cleaned effectively with household items, but if you plan to use a pressure washer, bear in mind the following. Pressure washers are incredibly powerful and without proper care or experience, using it to clean your composite decking can risk damage to the finish.

You should always contact your decking supplier to check whether it can be pressure washed. If you have uncapped decking, which doesn’t have a protective layer, avoid pressure washing as the surface can get easily damaged by the equipment. You can usually use a pressure washer on capped decking – but it's important to double check with the decking manufacturer beforehand. 

If you decide to go ahead, use a fan attachment where possible because it disperses water evenly on the board and reduces the risk of excess pressure on one spot. Never exceed 1,500 pounds per square inch (in your pressure washer settings) as this is too abrasive.

Make sure you keep a distance between the power washer and surface of the deck – 25-30cm is the advised distance. Washing too close can risk scratches and cuts. Finally, try to clean with the grain of the board to reduce the risk of scratching the deck.  

Does vinegar work for cleaning composite decking? 

Vinegar is safe to use on composite decking as long as you wash it off properly. It contains acetic acid which is effective in removing stains and dirt, and it’s readily available. 

To create your DIY cleaning solution, you mix half a cup of either white or apple cider vinegar with a one-quarter cup of baking soda, and three litres of water. The best way to clean composite decking using vinegar is by following the steps above, and switching out your washing up liquid solution with your vinegar one. 

Note: Vinegar contains acetic acid which can stain your deck if it’s left on for too long. 

How can you get moss and algae off composite decking? 

The growth of algae and moss on composite decking is common especially during the winter. It’s often caused by debris and leaves that remain on your deck which hold moisture. Removing any debris by sweeping regularly prevents the algae and moss from growing, and keeps your decking looking clean. It’s also a good idea to trim any trees that are close by to prevent leaves falling on it. 

To clean composite deck boards, you can use your homemade vinegar or soap solution, or purchase a composite deck cleaner which is specially formulated to remove algae. However, before purchasing any products, consult with the manufacturer to check if they’re suitable for the composite decking.

What to do if mould is growing on your decking? 

Mould growth on your decking is common, especially if you live in a wet climate and the deck is in the shade. Untreated mould can cause the composite decking to rot and break down, so staying on top of it is critical.

Uncapped decking is particularly at risk from the growth of mould as it doesn’t have a protective layer and it absorbs moisture. Luckily, removing mould from composite decking can be simple. You can use your vinegar solution or buy a composite deck cleaner formulated to remove mould, after checking in your product specification that it’s suitable for use. 

To prevent mould in the first place, you could go for a capped decking which is more water-resistant. Then, when installing the decking, ensure there is adequate spacing between the boards for ventilation. Although composite decking is manufactured to be long-lasting, regular cleaning and maintenance is essential to its durability. 


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