Can you pressure wash rendered walls? (Short answer: no)
We get called to a few render repair jobs a year that started as someone hiring a pressure washer from Bunnings. The damage is quick and it is not cheap to fix.
What pressure does to render
Acrylic render has a thin textured topcoat. High pressure erodes it, leaving smooth patches that are obvious once dry.
Around cracks and expansion joints, pressure gets behind the render and blows sections off entirely.
Water driven into a render crack sits in the substrate. On a lightweight system that means the sheeting behind, which does not dry out easily.
Repair means re-rendering a section and colour-matching, which rarely blends perfectly.
What soft washing render looks like
A detergent matched to the render type — acrylic, cement and textured all behave differently.
Applied at low pressure, given dwell time to kill the mould and algae rather than just wet it.
Rinsed at low pressure from the top down.
Care around windows, weep holes and light fittings, because those are the places water gets in.
Why the mould keeps coming back
South-facing and heavily shaded walls stay damp. Mould will always return faster there.
Garden beds and dense planting hard against a wall hold moisture in the render. Pulling plantings back 300mm makes a real difference.
Blocked weep holes trap moisture inside the wall system. Worth checking if one elevation is dramatically worse than the others.
A proper soft wash typically holds two to three years on a normal wall, less on a permanently shaded one.
Common questions
- Will cleaning strip my paint?
- Not with soft washing. Paint that is already chalking or failing may look worse once the dirt is gone, because the failure was being masked. We flag that before starting rather than after.
Need render cleaning in Melbourne?
Render cleaning in Melbourne. Mould, algae and staining removed from acrylic and cement render without stripping the finish.