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Render advice
Why Does Render Go Green, and Will It Come Back?
Green and black marks on render are very common. Here is why they appear and what helps.
The short answer
Render goes green and black when algae grows on damp, shaded surfaces. Cleaning removes it, but growth can return, because the conditions stay the same. How fast depends on shade, trees and exposure.
Why it happens
North-facing walls, walls shaded by trees or buildings, and walls near gutters that overflow stay damp for longer. Algae uses that damp to grow, and render is a textured surface that holds on to it.
What helps
- Keeping gutters and downpipes clear so walls do not stay wet
- Cutting back overhanging trees and plants where possible
- Having the wall cleaned before growth gets heavy
Cleaning without damage
We use a low-pressure softwash for most render, because high pressure can damage it. See our guide on pressure washing render for the detail.
Questions
Will the algae come back?
It can. We cannot promise it will not, and we will explain what to expect for your house.
Is it safe to jet wash render?
Not in most cases. See our guide on pressure washing render.
Can you clean painted render?
Yes, with a gentler approach, because the paint layer has to be protected. We assess first.
Related
Render cleaningCan you pressure wash render?Gutter clearance
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