How To Clean Composite Decking

Composite decks are so much easier to clean than any other decking material. Although composite decks require little maintenance, cleaning it is essential to reduce the risk of damage and extend its life.

This article will outline the most efficient and safest ways to clean your composite deck. Continue reading to find out what to do, what to avoid, and the best way to eliminate the common stains that affect composite decking.


How to Clean Composite Decking in 5 Easy Steps

Composite decking is made from recycled materials, wood fibres, and polymer plastics. Therefore, it is far more durable, low-maintenance, and easier to clean than timber decking. Despite the minimal upkeep, composite decking requires periodic cleaning to maintain its natural appearance.


What You Need

  • Soft bristle brush
  • Mild dish soap (ammonia-free)
  • Warm water
  • Bicarbonate of soda
  • Distilled white vinegar
  • One teaspoon of lemon juice


Step 1: Prepare Your Deck

The first step is removing all the furniture, potted plants, and accessories from your deck, so you can see any hidden dirt and debris around furniture and plants.


Step 2: Sweep Your Deck

Sweep your deck to remove any loose dirt. Use a hand broom to remove any dirt stuck to your composite deck, or use a vacuum to suck up loose dirt and debris.


Step 3: Rinse the Deck and Prepare a Soapy Water Solution

Before scrubbing your composite decking boards, rinse your deck with warm water. This will make scrubbing and removing dirt and stubborn stains from textured composite decking boards easier. Once done, mix two tablespoons of dish soap into a bucket of warm water.

If your deck is plagued by mildew or mould, mix one tablespoon each of lemon juice and bicarbonate of soda and a quarter of a cup of distilled white vinegar and add the mixture to the water. Using the soft-bristled brush, apply gentle pressure as you scrub away any mildew or mould. Use a toothbrush with soft bristles to scrub the spaces in between the deck boards.


Step 4: Scrub and Remove Dirt and Debris

Gently start scrubbing your composite deck using a soft-bristled brush and soapy water. Ensure that the bristles are soft; a hard bristled brush could leave scratches on the deck surface. Gently apply pressure to remove stubborn stains and get into the spaces between each decking board.

Top Tip: If your deck receives direct sunlight, it is best to clean your composite deck in sections. The sun might dry out the soapy water, leaving behind a filmy residue.


Step 5: Rinse Your Deck Thoroughly

Once you’ve finished scrubbing your deck, the most important step is to rinse away the soapy water solution. As mentioned above, you don’t want to be left with residue on your clean composite decking, so ensure that you rinse it thoroughly.


How To Pressure Wash Composite Decking

Cleaning composite decking with a pressure washer is possible, but follow the manufacturer’s guidelines to avoid damaging your deck. Pressure washing can be used on capped composite decking, but using a pressure washer on uncapped decking is not recommended since the boards are much softer and can damage easily.

  1. Always use a fan tip nozzle to wash your composite decking. The nozzle will disperse the water evenly and avoids concentrating on a specific area that could strip away the composite decking board’s protective layer.
  2. The best setting on a pressure washer to avoid damage is a maximum of 1,500 pounds per square inch (PSI). Do not exceed the PSI limit since this can cause cuts and scratches on the composite decking surface.
  3. Keep the pressure washer at a safe distance from the deck’s surface; at least 20 to 30 centimetres.
  4. To avoid unsightly scratches and cuts, clean with the grain and not against it. Use the pressure washer with each individual composite decking board to get the best results.

Note: Exercise caution when using a pressure washer and follow the manufacturer guidelines to the letter. It is essential to note that a pressure washer is best suited for cleaning composite decking instead of a power washer. Power washers use steam and may be less effective in removing dirt and debris.


Things to Avoid When Cleaning Composite Decking

Avoid using chlorine bleach products or bleach on your composite structure.

Bleach will cause your composite deck to fade and chip. It is incredibly corrosive and will eventually discolour and damage your deck boards.

Bleach and industrial cleaners contain harsh chemicals and should be avoided. Instead, use a cleaning product that is made specifically for composite decking. If you find the ingredient Sodium Hypochlorite listed on a composite deck cleaning product, avoid it at all costs. Sodium hypochlorite is a chlorine beach that will cause discolouration.

Always use a soft-bristled broom to sweep dirt and debris from your composite deck. Hard bristles will scratch your deck’s surface.


Common Issues Affecting Composite Decking

You can expect your composite deck to be exposed to dirt and grime over time. However, common issues can affect your composite deck, and the good news is that removing them is no hassle.


Mould and Mildew

Invasive mould and mildew are common issues that composite decking boards experience. Unlike traditional wooden decking, mould and mildew do not ruin the structural integrity of composite boards, but they can harm your health. Luckily, using soap and water and gently scrubbing your deck is all it takes to eliminate the mildew and mould.

If this doesn’t work, follow our tips above using lemon juice, vinegar, and bicarbonate of soda.


Food Spills

Your composite deck is a place where you can relax, have a drink, and enjoy a meal. Most spills come from accidentally dropping food or knocking over a glass.

Clean up any food or liquid spills with a paper towel and if that does not work, use the handy soap and water technique to remove any food debris. Even if you have grease stains from food debris, warm soapy water should be all you need.


Oil and Grease

In the summer months, we want to enjoy juicy steaks on the grill, and the issue is stray oil and grease splatters landing on your composite decking boards. Grease and oil can cause discolouration and permanent stains on composite decking, so they should be cleaned up as soon as possible.

Use a soft-bristled brush, warm water, and soap to remove grease and oil stains.


Snow and Ice

Winters can be harsh with heavy snowfalls; however, composite decks are engineered to withstand the harshest weather elements. Removing ice and snow often only requires a plastic shovel. Avoid using a metal shovel since this can cut and damage your composite deck.

To remove snow quickly, use a leaf blower or a broom before gently scraping off the ice underneath. To remove stubborn ice that won’t budge, use calcium chloride to melt the ice before gently proceeding with the plastic shovel. Avoid using a snow blower since it can cause cuts and abrasions on the deck’s surface.

Note: Once the ice has melted, remove all traces of the salt from the composite deck boards to avoid damaging the deck surface. Please exercise caution; ice could cause you to slip, fall and injure yourself.


Pollen & Seeds

Pollen, leaves, and seeds will naturally make their way onto your deck if plants and trees surround it. Although pollen dust does not cause long-term harm, cleaning pollen from composite decking as soon as possible is a must.

If left alone, pollen, seeds and dirt can cause a biofilm. Mould can feed off the biofilm, which causes it to spread, creating an avoidable issue with mould on your composite deck. The best solution is to use a pressure washer to remove pollen debris from your composite deck.


Hard Water Stains

Hard water stains are a combination of lime, silica and calcium. As water evaporates, it leaves behind an unsightly residue. You can find a composite decking cleaner that can remove hard water stains. Ensure the product is made for composite decking to avoid damaging your composite deck.

White vinegar is pretty effective in removing the hard water stain build-ups. Leave the white vinegar on the stain for a few minutes before gently washing it away with water.

Important Step: Dry the area immediately with a dry towel or blower.


How To Extend the Lifespan of Your Composite Deck

In addition to cleaning your composite deck regularly, there are a few things you can do to maintain and extend the longevity of your deck.

  • Deep clean your composite deck at least twice a year. Spot cleaning should be done as needed – like when you notice something has been spilt on the deck.
  • If you notice mould and mildew forming, use the soap and water method or the bicarb vinegar mixture to remove it. Ensure that your deck is kept dry. Use a clean towel to remove any moisture.
  • Keep an eye out for any drainage issues. Although composite decking is resistant to rot and moisture, the underside of your deck may not be. The soil under your composite deck should absorb moisture and prevent water from pooling, and if it does, you may need to replace the soil.



Can you use vinegar to clean a composite deck?

Although vinegar is generally safe for composite decking, it is not the ideal cleaning solution. However, distilled white vinegar with other products like bicarbonate soda effectively removes debris and stains. Avoid leaving vinegar on the decking surface for longer than necessary, and always ensure you rinse off the vinegar thoroughly.


What household items can I use to clean my deck?

Natural products like lemon juice, distilled white vinegar, and bicarbonate soda combined with water effectively remove mildew, mould, and algae from composite decking. Always rinse your deck with clean water afterwards to remove residue.


What should you not use on a composite deck?

Never use bleach, harsh chemicals, or cleaning products containing chlorine bleach on composite decking. Always try the soap and warm water method on your deck boards first. If this specific cleaning method is unsuccessful, try using an oxygenated cleaning product like Oxylyse to clean composite decking.


Can I use patio cleaner on composite decking?

Composite decking is a porous material, and most patio cleaners contain harsh chemicals that can harm the surface of your composite deck. Instead, use an oxygenated cleaner designed specifically for composite decking.


Final Thoughts

Even though composite decks require little to no maintenance, it is essential to take the necessary steps clean and sweep away loose debris and dirt. To avoid causing irreversible damage to your composite deck, follow the manufacturing guidelines when using a power washer and use the soap and water method for basic cleaning and upkeep.

Gary is the founder and CEO of Ecoscape UK. Gary graduated from Liverpool JM University in 2007 with a 2:1 in Economics. A passion for innovation, design and sustainability, Gary has put to market numerous wpc products/systems, some of which have UK and European registered designs. Outside of work Gary enjoys spending time with his family, the great outdoors and watching Manchester United.