Silicone render is a thin-coat finish, often only around 1.5 to 2 mm thick, applied over a base coat and mesh. Its silicone resin makes water bead and run off, which is why it is so popular on new builds and extensions. It is not immune to algae, though. On north-facing walls, under trees and below sills, growth still takes hold, and because the finish is so thin, aggressive cleaning can wear through the top coat and leave patches that look different from the rest of the wall.
The safe approach is to let the chemistry do the work. A biocide suited to silicone render is applied at low pressure, left to dwell so it kills the algae and mould at the root, then rinsed off evenly across the whole elevation. Some render manufacturers make their own cleaning and maintenance products for their systems, and where the house still has a render guarantee, it is worth checking the manufacturer's maintenance advice before work starts.
What is included
- Checking the render is silicone and noting any cracks or damage
- Protecting plants, windows, doors, vents and paving
- Wetting down surrounding planting before cleaning
- Low-pressure application of a biocide suited to silicone render
- Dwell time for the biocide to kill growth at the root
- Even, low-pressure rinse of each full elevation
- Optional protective treatment to slow regrowth
- Walk-round check and aftercare advice
Who it is for
- New builds and estates finished in silicone render
- Extensions where silicone render has turned green
- North-facing and shaded walls on modern homes
- Homes still under a render system guarantee
- Housebuilders and managing agents maintaining several properties
How much does it cost?
As a guide, cleaning silicone render usually costs £4 to £8 per square metre, or around £300 to £600 for a typical semi-detached house. A protective after-treatment usually adds £1 to £3 per square metre. See our full cost guide.
