Can green render be cleaned? Yes. On silicone and monocouche render we use a soft wash — low pressure and a biocide that kills the algae and mould at the root — not a pressure washer, which can scour the finish and drive water in. A biocide is left on to keep regrowth back, a protective coat goes on after, and if cleaning alone will not bring it back, we can re-colour it.
Why render goes green (or black)
The green is algae and moss; black patches and streaks are usually mould and dirt washed down from sills and gutters. All of it grows where a wall stays damp: north-facing elevations, walls shaded by trees or the house next door, and anywhere water runs down the face.
Even silicone render, which is sold as self-cleaning, can grow algae on a wall that rarely dries out. It does not mean the render has failed — but left alone, the growth holds moisture against the surface and the wall only gets worse.
Why we soft wash, not pressure wash
A pressure washer removes what you can see and leaves the root behind. It can also scour the coloured surface of a monocouche, open up hairline cracks and force water behind the render. The growth comes back sooner, and the wall can end up worse than it started.
A soft wash works the other way round. The biocide kills the algae, moss and mould where they are rooted, and a low-pressure rinse takes them away. The finish is left as it was, just clean.
What a render clean includes
- A free look and a fixed quote — we see the walls before we price them.
- Soft wash with a biocide — low pressure, killing the growth at the root.
- Biocide left on the wall to keep regrowth back after we have gone.
- A protective coat applied once the wall is clean.
- A check for cracks and blown render as we go, with a separate quote for any render repair.
- Re-colouring if cleaning alone will not bring the colour back.
The renders we clean
We clean silicone render and monocouche render — the two systems we apply ourselves, so we know how each surface behaves. Not sure which yours is? See silicone vs monocouche, or just send us a photo.
If your walls are painted sand and cement or pebbledash, get in touch and we will tell you honestly whether re-rendering is the better spend.
When cleaning is not enough
Sometimes the staining has gone into the colour, or the render underneath is cracked or hollow and letting water in. Cleaning a wall like that only treats the symptom. We will tell you what we find, re-colour the render where that is the answer, and quote any repairs separately so you can choose.
What it costs
Every wall is different — the size, the access, and how far the growth has gone — so we price after a look rather than guess. The quote is free and fixed, there is no call-out charge for it, and we take no deposit. For re-rendering prices, see rendering costs in Sheffield.
What happens next
Send us a photo or book a free look. We check every elevation, tell you honestly whether a clean will do it or the render needs more, and give you a fixed price. You pay when the work is done and you are happy with it.