The correct method of how to remove algae from patio slabs, can depend on what material you're working with. The common go-to method used to clean patio slabs, the pressure washer, won't be sufficient for tackling the organisms present in algae.
Generally speaking, specialist algae and mould remover products are formulated to work on most common patio surfaces without damaging them, however, some may prefer to opt for a gentler and cheaper approach with natural solutions.
Experts share their tips below for how to get rid of algae as well as addressing some of the potentially problematic conditions of your patio to try and prevent algae from flourishing.
1. Keep your patio clear of debris
Steven Walley, outdoor flooring expert from London Stone recommends preventative measures for avoiding algae buildup on your patio.
“Fallen damp leaves can cause significant problems for your patio or decking. If left untreated or left to settle for a long time this can cause the growth of algae which can not only stain your outdoor flooring but also lead to slippery surfaces," says Steven.
“It’s important to stay on top of cleaning your outdoor decking and patio flooring all year round to avoid this, especially as we look towards the warmer months when we’ll be using our outdoor spaces more.”
Removing debris is also an essential first step in tackling your algae problem.
(Image credit: Getty Images)
2. Select the right cleaner
"Watch out for acid or bleach-based cleaners as these can damage the patio surface, and instead opt for a soft, non-destructive patio cleaner," says Dr Jonathan Kirby, Garden and Cleaning Expert at Roxil.
Mark Atkins, Director at LTP, manufacturers of stone and tile protection and maintenance products, recommends avoiding cleaning methods for removing algae in patios and block paving which use excess amounts of water which can make the problem worse.
"Any treatment used needs to break down the slippery residue, have a bleaching action to restore the colour of the paver and target growth below the surface," says Mark.
Beware of acidic products which can erode grout joints. Angela suggests you check that the product is suitable for your patio material whether that be natural stone, concrete, brick or porcelain paving.
Shop patio cleaner for algae
Patio Magic!
This solution can be used on patios, driveways and masonry, for effective removal of algae. You will need a spray kit to apply it to your slabs.
Wet & Forget Mould Lichen & Algae Remover - 2l
This neutral solution contains no bleach nor anything which could damage your patio surface. Simply apply and leave it to do its work with no scrubbing needed.
Karcher T5 Racer Patio Cleaner
This can be used with your chosen patio cleaning solution (subject to manufacturers guidance) and makes for effortless and mess-free cleaning.
(Image credit: Shutterstock)
Mark Atkins
Mark is the Director of LTP, one of the major suppliers of sealing cleaning and maintenance products to the tile and stone market.
3. Consider natural cleaners
Steven Walley advises using vinegar to kill algae growth on your patio paving as while bleach is generally safe for concrete patios it can damage natural stone such as granite or slate.
To use vinegar to treat algae growth, Steven says: “Use a mixture of water and white vinegar to spray down the area and kill the algae before rinsing the surface with a hose. Next, pour white vinegar directly on the surface and scrub using a brush. Use a vigorous back and forth motion to lift any stains.”
Consider however that vinegar may not be suitable for all pavers: "The use of acidic solutions should be avoided, particularly on calcareous pavers such as those made from limestone. Use on these pavers can lead to irreparable damage of the material," warns Trevor Knight, technical garden and driveway specialist for Marshalls Plc.
If you are concerned about how your chosen mould removal method might affect your patio then try a small test patch in an inconspicuous area before you start and monitor the results.
(Image credit: Getty Images)
Steven Walley
Managing Director of London Stone supplying the landscaping, construction and garden design industry
4. Pressure washing alone won't kill algae
Whilst being effective at blasting away dirt and grime, a pressure washer alone won't kill the spores which, if remaining will cause the algae to regrow. Excessive use of pressure washers can also be damaging to your patio.
"While it may be tempting to blast away algae with your pressure washer, this won’t be able to completely remove green algae," says Dr Jonathan. "If consistently used on the surface, it also damages wooden surfaces like patios and decking, and if used for cleaning a fence, and blows out pointing and dispersing jointing sand."
(Image credit: Getty Images)
5. Avoid abrasive methods for porcelain
Steven Walley urges you to avoid using abrasive materials on your porcelain tiles, as these could damage or scratch the surface of your tiles.
“Avoid cleaning porcelain paving slabs with steel wool or a steel brush, as these could scratch the surface or leave particles in your patio grout, which could oxidise, causing discolouration," Steven says.
“Instead, opt for a gentle, soft cloth or a mop to complete the job and scrub grout lines with an old toothbrush, to help protect your pavers."
Dr Jonathan Kirby explains that washing and treating a patio fully will require some waiting time to allow your cleaning and treatment products to work effectively. He suggests you choose a sunny day to give your products the best chance of taking effect
"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 your patio. Leave for between 1 and 24 hours to kill and loosen biological growth and dirt, washing away with a hose afterwards," says Dr Kirby.
(Image credit: Shutterstock)
7. Improve water tightness and drainage
Dr Kirby recommends a protective sealer as a preventative measure for algae growth on your patio slabs.
"Make sure the patio is completely dry before applying small amounts of a protective sealer, like Roxil Patio Cream, directly to the patio using a brush or roller, and leave it to absorb into the stone or slabs for 24 hours," says Dr Kirby.
“A surface water drainage system that reduces the amount of time you have standing water on your patio is also important, as that's where algae and other organisms tend to thrive," he adds.
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.
Once you've spruced up your patio and restored it to its former glory, think about bringing some fresh greenery and floral interest with new patio planting ideas.
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Teresa was part of a team that launched Easy Gardens in 2018 and worked as the Editor on this magazine. She has extensive experience writing and editing content on gardens and landscaping on brands such as Homes & Gardens, Country Homes & Interiors and Living Etc magazine. She has developed close working relationships with top landscape architects and leading industry experts, and has been exposed to an array of rich content and expertise.
In 2020 Teresa bought her first home. She and her partner worked alongside architects and builders to transform the downstairs area of her two bedroom Victorian house in north London into a usable space for her family. Along the way she learned the stresses, woes and joys of home renovation, and is now looking to her next project, landscaping the back garden.
