A good render can transform a house. As well as smartening up tired brickwork, it can help keep exposed walls dry and warm. Through-coloured renders such as K-Rend, monocouche and silicone-based renders are sold as low-maintenance, but on damp, shaded or north-facing walls they can still turn green, black or grey within a few years. Here’s how to clean K-Rend safely, and what not to do.
Why K-Rend goes green
The marks on most stained render are organic: algae, moss and lichen, plus the dirt and pollution they trap. They thrive where walls stay damp, so they tend to appear first under windowsills, near gutters and downpipes, and on walls that don’t get much sun. Because the growth lives in the surface of the render, simply washing the dirt off isn’t enough. It comes straight back.
Don’t pressure wash render
It’s tempting to blast the green away with a pressure washer, but high pressure can damage the surface of the render, strip its finish and drive water into it. I never use high pressure on render.
Softwashing: the safe way to clean render
Softwashing uses low pressure and a cleaning solution designed to kill the algae, moss and lichen at the root rather than just washing the surface:
- a green growth treatment is applied first to break down the organic growth
- the render is then cleaned gently at low pressure, lifting stains caused by algae, pollution and weathering
- it’s rinsed, leaving the surface clean
The same gentle method works for K-Rend, monocouche and silicone renders, and for painted render, brickwork and other delicate surfaces.
Keeping it clean
Once render is clean, a periodic maintenance treatment helps stop the growth from coming back so quickly, which makes the next clean easier and cheaper. If you’d like to try a small area yourself, use a soft brush and a cleaner your render manufacturer approves, test it somewhere out of sight first, and never use high pressure.
Get a quote
I clean render on homes and commercial buildings across Wolverhampton. Send a photo, your postcode and a short description to 07754 405080 by WhatsApp or text, and see more about my render cleaning and softwashing services.
