Guide
Will power washing damage my render? Soft washing explained
Updated
The short answer
High-pressure washing can damage render, painted finishes and pebbledash by stripping paint, forcing water into cracks and blowing out loose material. Soft washing, which uses low pressure and a cleaning treatment that kills algae at the root, is the safer way to clean the outside walls of a house, and the results last longer.
What goes wrong with high pressure
A pressure washer concentrates a lot of force on a small area. On render and painted walls that can lift paint, erode the surface, drive water behind the render through hairline cracks, and loosen pebbledash. It also only removes what it hits: the roots of the algae stay in the surface, so the green comes back quickly.
How soft washing works
Soft washing applies a cleaning solution at low pressure, gives it time to break down the algae, lichen and grime, then rinses it off gently. Because the treatment kills the growth rather than just knocking the top off, walls stay clean noticeably longer.
- Safe for render, painted walls, pebbledash and most cladding
- Cleans fascias, soffits and gutter fronts at the same time
- Plants and windows are protected or rinsed down
Why Irish walls go green
Walls that stay damp and see little sun, usually north-facing or shaded by trees and neighbouring houses, are where green algae and black streaks build up. Near the coast, salt adds a dull film. None of it damages the wall in itself at first, but it holds moisture against the surface and looks tired.
Clean before you paint
If you're planning to repaint, clean first. Paint applied over algae and dirt doesn't bond properly and starts to fail early. A soft wash a little while before painting is the cheapest way to make a paint job last.
Questions
How long does a soft wash last?
It depends on how much shade and rain the wall gets, but because the treatment kills the algae rather than just rinsing it, it lasts much longer than a pressure wash.
Is soft washing safe for my plants?
With care, yes. Plants near the walls are wetted down or covered first and rinsed afterwards.