How to remove algae from decking — experts reveal the best ways to banish the green and bring your decking back to life

If you have decking in your garden, chances are it's been neglected over the winter months and it's now shrouded in algae and moss and - truth be told - looking pretty unsightly.

Appearance aside, algae is an unwanted invader for your decking as it makes surfaces very slippery, posing a safety risk. More importantly, if left untreated, the green substance can begin to rot your decking.

Not sure where to begin when it comes to how to clean decking? The good news is that there are a few options to help you restore this area of your garden to its best state. You'll soon be ready to crack on with your decking ideas (and if you need inspo - from decking rail ideas and how to paint decking, we've got you covered!) and get your space in tip-top shape for summer.

That being said, it's worth weighing up the various options for how to remove algae from decking as experts warn there is one popular garden gadget that can be counterproductive if not used correctly.

Prepare the decking

The key is to tackle algae removal as early as possible and stop it from spreading further, according to the professionals.

'Algae grows in shady areas, especially if the area is moist. This grows quickly on wood, so wooden decks can be the perfect environment for algae to spread,' says Morris Hankinson, director of Hopes Grove Nurseries.

Whatever method you opt for when it comes to how to remove algae from decking, the first thing you'll need to do is make sure the area is clean and tidy. Worth noting too, although you might follow a different method when it comes to how to clean composite decking, algae can cause issues for both types of decking.

'You should always start by sweeping away any loose dirt and debris and removing any furniture. This is an important step because furniture and debris can trap moisture and therefore create the perfect breeding ground for algae,' says Lee Trethewey from Sustainable Furniture.

Morris Hankinson

Morris Hankinson is the founder and managing director of Hopes Grove Nurseries Ltd, the UK’s only specialist grower-retailer of hedging plants. He established the thriving business in 1992, shortly after graduating with a Commercial Horticulture Degree from Writtle College, Essex.

1. Use a pressure washer

Thankfully, there are a few different techniques when it comes to how to remove algae from decking and one of the most effective ways is to use a pressure washer, advises Morris Hankinson.

'Pressure washing is by far the easiest way to clean decking off algae. The force of the water will wash it off very quickly, especially if applied with a safe, organic solution specifically for decking,' he says.

However, if you are using a pressure washer, you'll need to approach carefully to avoid a decking mistake, warns Graham Smith MCIHort from LBS Horticulture. 'If not used correctly or carefully, a pressure washer can damage or etch the surface of the deck.

'Ideally, use a fan or spray nozzle to distribute pressure evenly, and ensure that you are holding the nozzle at least 30cm away from the surface of the decking,' he says.

If you decide to invest in a pressure washer, knowing which one to get can be a bit of a minefield but fear not, as we've researched the best pressure washers for you. Our tried and tested top pick is the Karcher K4 available on Amazon.

Using a pressure washer can get pretty messy so you'll need to clean up afterwards, and make sure you fully rinse the decking to wash away any of the residue. 'It'll prevent the decking from becoming excessively slippery and dangerous,' says Lee.

Graham Smith MCIhort

Graham Smith MCIhort is the gardening expert at LBS Horticulture. He has extensive knowledge in the horticultural and gardening industries, and prides himself on using this to help gardeners of all skills create their perfect outdoor space.

2. Scrub with soap and water

If you don't fancy risking it, you'll be pleased to hear there is a natural (and less costly!) remedy than a pressure washer when it comes to how to remove algae from decking.

The key ingredient, believes Morris, is some elbow grease! 'You can use a stiff brush and a mix of warm water plus liquid soap to scrub the algae off,' he says. This Charles Bentley Stiff Wooden Hand Scrub Brush from Amazon is a good option for scrubbing outdoor garden areas.

When scrubbing, you should make sure you're brushing in the direction of the wood grain' advises Lee. 'This will avoid causing any damage such as scratches and splinters in your decking.'

Focus on stubborn areas and repeat the process if necessary.

3. Use a white vinegar solution

Another natural (and eco-friendly) remedy is to use a white vinegar solution to kill algae without harming your decking.

'White vinegar is a natural cleaner that can be used outside as well as inside,' advises Graham. 'Dilute a small amount of vinegar in water, and use this solution to scrub the deck and remove algae,' he says.

For best results after applying the solution (this White Vinegar Multi-Purpose Cleaner from B&Q comes highly rated), Morris recommends leaving it to sit for about 15 minutes before scrubbing with a stiff brush.

'Leaving the white vinegar solution for a maximum time of 15 minutes is enough to allow it to get to work on the algae before rinsing off but not long enough for the acidity of the vinegar to damage the decking,' he says.

4. Try specialised algae removal products

Whilst we'd advise trying to avoid using chemical cleaners, you may need to use a strong cleaning solution for stubborn algae that won't budge.

'There is a wide range of specialist algae removal products available that are specifically designed to remove algae from decking, but they can be more expensive than other DIY solutions,' Graham Smith advises.

'Bleach is sometimes recommended to remove algae from decking, but this is not the best thing to use. The bleach can damage the decking itself regardless of if it is wooden or composite, and it's also harmful to plants and animals.' Graham adds.

This Algon Organic Patio Decking Cleaner gets our vote as it is eco-friendly and non-toxic, making it safe to use around pets and wildlife.

Decking cleaning essentials

FAQs

Does vinegar damage a wood deck?

Vinegar can work wonders as a remedy for how to remove algae from decking, but it can also damage the wood if you don't use it correctly. The experts say the trick is to dilute it first, and be careful not to leave the vinegar on for too long.

Lee Trethewey from Sustainable Furniture advises, 'If you're going to use vinegar to clean decking, make sure you dilute it a lot with warm water using a 1:4 ratio.

'You should also avoid using vinegar frequently on decking, and if your decking has been sealed, painted or varnished, you should avoid using it altogether so as not to ruin the coating. Make sure to patch test first, on a very small piece of decking.'

How do I prevent algae regrowing on my decking?

So now you know how to remove algae from decking, one question remains: how do you eliminate algae from your garden space for good?

Keeping your decking regularly maintained will help to prevent algae making an unwelcome return, says Graham Smith from LBS Horticulture.

'Do not allow debris to accumulate on the surface of the deck, as this will create a barrier that stops sunlight from reaching the surface and provides the ideal breeding ground for algae.

'You should also check that moisture can't gather on any part of your decking, as this helps algae to grow. Most decks should have enough space between boards to allow water to drain away, and you can seal the deck with a water repellent sealant to help keep it dry,' he says.

Morris Hankinson from Hopes Grove Nurseries adds, 'If the decking is shaded by trees or hedging, if you can cut it back to tidy and allow some light through, this will also help. Always reseal the decking after cleaning it, which will provide a barrier between the wood and sitting water and give it a good clean once a year so algae can’t build up and cause problems.'

So there you have it: how to remove algae from decking and just in time for garden season. You might want to tackle removing algae from a fence next...

Happy cleaning!