Life Hack: How to remove algae from patio slabs and concrete ahead of the longer evenings
Algae can build up on patios, concrete and other surfaces in shady areas that don’t get a lot of sunlight
With the clocks changing over the weekend, I’m already dreaming of long spring and summer evenings spent relaxing in the garden — just keep your fingers crossed for good weather this year. However, the patio area in my own garden is in need of some TLC after a long damp winter as some corners have developed patches of green algae, a common problem in Irish gardens due to our climate.
Algae, as well as moss, can build up on patios, concrete and other surfaces in shady areas that don’t get a lot of sunlight (for example, my patio in winter). Porous surfaces, like sandstone and limestone, allow more air and moisture into them too, leading to a buildup of algae. Generally, the build-up of algae is more likely to happen during the autumn and winter months as there is less sunlight and more rain.
This can be unsightly to look at and poses a potential slip hazard. It is easier to clean the algae in dry weather as there is increased sunlight and reduced moisture in the air, so spring is the perfect time to tackle the issue as you can then enjoy the brighter months in your spick and span, algae-free outdoor area.
There are a few steps you can take to remove algae.
Vinegar is a useful product to have for many reasons and yet again it comes in handy for this cleaning situation. White vinegar diluted in water can remove algae when sprayed on the surface.
It is less damaging to the surface than bleach but the acid it contains could damage some natural stones, particularly those with a high lime content. For that reason, you should first test this method in a concealed spot on your patio before applying widely to avoid any issues.
If you don’t mind applying some elbow grease, you can scrub your outdoor area with a mixture of soap (like washing up liquid) and hot water. This will remove the algae but it is more time-consuming and physically damaging than the ‘spray and wait’ options. Wait for it to dry after you have scrubbed the area and treat any missed spots with the same method.
A pressure washer can remove the algae easily but it is only a short-term solution and not recommended for several reasons. This method may remove the protective grout from between patio slabs, which would need replacing. In addition, pressure washers could make the tiles more porous, which can make them dirtier and more likely to develop algae faster, meaning you would end up cleaning them more frequently.
For more stubborn algae, a commercial cleaner can also be used in the area. Many of these will also help to prevent future build-up.
If you find yourself tackling algae buildup frequently, you’re probably wondering how to prevent it from developing in the first place and save yourself the hassle of treating it annually. Due to our climate, algae buildup is very difficult to fully prevent.
However, there are some steps you can take to reduce those green deposits.
Algae thrive in damp and shaded areas. In contrast, sunlight is a natural deterrent for it to grow on surfaces so increasing sunlight exposure to the area can naturally deter its growth.
You can ensure sunlight reaches more of the area by trimming trees and shrubs and cutting back overhanging branches and dense foliage that may have been shading the area.
Planters and outdoor furniture can trap moisture too, creating ideal conditions for green growth. these items should be moved around regularly to help prevent algae growth.
At the installation stage, choosing less porous materials like slate and granite will help to prevent algae buildup. In addition, good drainage will help to prevent excess moisture from building up.
This can be achieved by having a slight slant on your patio for drainage. You could also install drainage channels to move water away from the algae-prone areas, keeping them dry and less likely to see green growth.
