Roughcast and Render Cleaning: Why We Never Blast Your Walls

Walk down almost any street in Lanarkshire and you will see it: roughcast and render with green and black streaks running down from the sills and under the gutters. It is algae, and in a climate as wet as ours it is almost impossible to avoid. The good news is that it cleans off. The bad news is that the obvious way of cleaning it, a pressure washer on full power, is the wrong way.

Roughcast is small stones bedded into a cement coat. Hit it with a concentrated jet and you can knock those stones out, leaving bald patches that are obvious once the wall dries. Smooth and painted render has its own problems: high pressure can cut into the surface and push water behind it, where it sits and causes trouble later.

Pressure also only removes the algae you can see. The roots stay in the pores of the render, so a blasted wall often goes green again within a season.

A soft wash uses a cleaning solution to do the work instead of pressure. The solution is applied at low pressure and left to kill the algae, lichen and bacteria right down to the root. Then the wall is rinsed gently. The render stays intact and the wall stays clean far longer because the growth has been killed, not just knocked off the surface.

We go through both methods properly in soft washing vs pressure washing. In short, pressure suits hard ground and soft washing suits walls and roofs.

Clean render next to a filthy sill looks odd, so we do the details as part of the job. This window sill was photographed halfway through, and the difference is obvious. The UPVC above it gets the same care as part of our soffit and fascia cleaning.

If your render is streaked but sound, with no cracks or loose patches, a soft wash will usually bring it back. If it is cracked or blowing, we will tell you before we start. Cleaning won't fix that and could make it worse.

We clean render and roughcast across Glasgow, Motherwell, Coatbridge, Bellshill and everywhere within 15 miles of Uddingston. See the render and cladding cleaning page for what is included, or request a date.