Guide
K Rend and silicone render maintenance: cleaning cost and care
Updated
Through-coloured render does not need painting, but it does go green. Here is what keeping it clean costs, and the one mistake that ruins the finish.
Why render goes green
Algae grows wherever a wall stays damp: north-facing and shaded elevations, under leaking gutters, behind vegetation. Silicone renders resist it longest because the surface sheds water, but no system is immune, K Rend and similar coloured renders will green up in the wrong spot too. The staining is organic, sitting on the surface, which is why it cleans off, and why cleaning is a maintenance line, not a defect.
What cleaning typically costs
- Soft washing (low pressure plus a biocide): typically £3–8 per m2 on 2026 quotes, so a 110 m2 semi lands roughly £330–£880, though many firms quote a flat job price with a minimum charge. Typical quotes, varies by access and how far gone the wall is.
- Biocide treatment after the wash slows regrowth, often included, worth confirming.
- Scaffold or reach equipment: most cleans are done from telescopic poles without scaffold, one reason cleaning is far cheaper than rendering.
The care rules
- Never jet wash at close range. High pressure strips the texture, opens hairline cracks and drives water into the coat. Soft wash only.
- Check the system maker's guidance before chemicals, silicone, mineral and acrylic top coats tolerate different cleaners.
- Fix the moisture source: a cleaned wall under a leaking gutter is green again in a season.
- Sand and cement is different: it is painted, so its maintenance cycle is repainting every 5–10 years rather than washing.
A note on names: K Rend is a brand (Kilwaughter Minerals), used loosely for coloured silicone renders generally, the way Hoover means vacuum. This site is independent and not affiliated with K Rend or any manufacturer.
Weighing up a re-render because the wall looks tired? Price a clean first, then compare it with the calculator's re-render range.