Experts reveal the fastest way to remove algae from decking — including cost-effective DIY solutions

Discovering what is the fastest way to remove algae from decking means saying goodbye to slimy, slippery surfaces and saying hello to a crisp, clean deck that not only looks good but is also safe to walk on.

No one wants to see their beautifully built garden decking ideas spoiled by algae, or even lichen and moss. But to keep it looking good, you need to use the right tools, products, and solutions. Here, the experts reveal their simple but effective tips for keeping decking clean and algae-free.

Dr Jonathan Kirby

Dr. Jonathan Kirby is a developmental chemist and Garden and Cleaning Expert at Roxil. From landscaping to masonry protection, he has dedicated himself to helping protect UK housing stock through the development of new and innovative materials.

How to quickly remove algae from decking

To quickly remove algae from decking, there are a few factors to consider. Here, Dr Jonathan Kirby, Garden expert at Roxil and Mark Irving, Building expert at Build & Plumb, offer their essential tips to swiftly say goodbye to unwanted algae, lichen and moss.

1. Choose a sunny day

Kirby says, “Washing and treating wooden surfaces fully requires some waiting time to allow your cleaning and treatment products to work effectively on the surface.” He suggests, “Choose a sunny day to give your products the best chance of taking effect.”

2. Avoid bleach-based cleaners

“Use a stiff wooden brush to sweep away any loose debris from the area you want to treat,” suggests Kirby. “Then, choose your cleaner, but watch out for acid or bleach-based cleaners, as these can damage surfaces and irritate the skin.” He recommends, “Choose a gentle, non-destructive cleaner," like this Roxil Wood & Patio Cleaner from Amazon.

3. Use low power on a pressure washer

There are a few reasons why you shouldn’t pressure wash a deck, as Kirby points out, “Blasting away with a pressure washer won’t completely remove black spot lichen.” And, he adds, “If consistently used on surfaces, it can lead to damage over time.”

However, used correctly, a pressure washer can be a useful tool, says Irving, “Ensure that you use a low to medium power setting to avoid damaging the surface of the decking.”

4. Leave cleaner to do its work

When adding a cleaner, Kirby says. “Wear gloves to protect the skin and then apply the cleaner with a spray or wire brush, either neat or diluted depending on the space/size of the surface area.”

He adds, “Leave for between 1 to 24 hours, (check manufacturers' recommendations), to kill and loosen biological growth and dirt, washing away with a hose afterwards.”

5. Try DIY cleaning solutions

To remove algae from composite decking Irving says, “Use a mixture of bicarbonate of soda and white vinegar in a bucket of fresh water.” He adds, “This solution should be poured or sprayed over the decking and left for 10 to 15 minutes to break down the algae. Then you can go in with a soft brush and gently scrub the surface of the decking until the algae has lifted.”

To finish, Irving continues, “Always fully rinse your deck after cleaning to ensure that the solution has been fully removed.”

For timber decking, Irving has another DIY solution: “Take a bucket of water and combine it with one cup of distilled white vinegar, then pour the mixture on the decking and leave it to soak for 10 to 20 minutes.

He adds, “After 20 minutes, use a gentle bristled brush to scrub the surface of your decking and finish by fully rinsing the decking with fresh water.” Why use white vinegar? “White vinegar contains acetic acid, which makes it beneficial in cutting through dirt and stains.”

Try these to help keep your deck algae-free

Mark Irving

With over 20 years of experience in the building sector, Mark led Build & Plumb’s expansion into online marketplaces. Over the years working for Build & Plumb Mark has developed a wealth of knowledge surrounding building and renovating.

Tools and solutions to use

To get rid of algae, you need a few tools. You can use a simple, stiff-bristled brush like this Sweeping Brush Outdoor Broom from Amazon. Or a pressure washer like this GUIFIN Electric High Pressure Washer from Amazon. Don’t forget to use it on low power.

If you using specialist products, Kirby says, “I would recommend treating the wood with a biocidal cleaner before applying a wood stain preserver like Roxil Coloured Wood Stain Preserver, which will provide a bright colour and lasting protection from UV and wood rot.

Irving says, “The brand Azpects has the Azpects 750ml EASYCare Algae Remover Spray bottle, an easy care spray algae remover that provides quick results that last up to 12 months”.

FAQs

What algae appears on decking?

Algae on decking is a regular occurrence, and there are a couple of common species often seen on wooden decking. Irving states, “Green algae is the most common type of algae that you will see on your decking, this is characterised by its green colour and slimy texture." He adds, “Typically, green algae thrive in damp and shaded locations.”

Another common visitor to wooden decking is black algae, which is slightly different to green algae, as Irving explains, “Black algae is another common form of algae. It can form in both the sun and shade and is characterised by its black colour and slippery texture.”

Unfortunately, both green and black algae will happily form together when conditions are right. Black algae are typically more difficult to remove and more likely to stain. So it makes sense to regularly remove dirt, leaves and debris, especially through the winter months when a deck sees more moisture.

How can I stop algae from coming back?

Removing algae is the first step in the fight to keep your deck clean and algae-free. The next is to prevent it from growing back. Irving says: “Regularly sweeping your decking to remove loose dirt, debris, and stagnant water can help to prevent the development of algae on the surface of your decking.”

Additionally, you will need to clean regularly, as Irving shares, “Simply wash your decking with hot water and washing up liquid every few months.”

Once your decking is clean and dry, the next step is to add protection, as Kirby shares, “Once it’s clean, it’s time to waterproof.” He adds, “Make sure the surface is completely dry before applying small amounts of a protective sealer, like this Barrettine Wood Protective Treatment from Amazon, directly to the surface using a brush or roller, and leave it to absorb into the surface for 24 hours.”

Irving offers a final tip to prevent moisture from reaching your decking: “If your decking is in an open location, it can be more susceptible to moisture from rain.” He continues, “During the winter months, it can help to place a cover – or something similar – over your decking to better protect it from the elements."

Keeping your deck clean and free from algae, moss, and lichen is essential to keep it looking good. Try one of the best decking paints to add a touch of colour to your latest raised decking ideas, and follow our painting decking guide to ensure a great finish.