The actual difference.
Water blasting is high pressure. It is a mechanical fix — the force strips material off the surface. Right for concrete, pavers, and hard exterior surfaces that can take it.
Soft washing, which is what "house washing" usually means, runs at roughly garden-hose pressure and does the work chemically. A treatment is applied, it kills the mould, lichen and algae at the root, and it is rinsed off. Right for cladding.
The distinction matters because most of what discolours a Wānaka house is not dirt. It is biological growth, and pressure only removes the part you can see.
Why pressure is the wrong tool for cladding.
Blast a weatherboard or plaster-clad house and you can force water up behind the boards and past the flashings. That water then sits in the cavity where nothing dries it out. In a climate that freezes overnight for a good part of the year, water sitting in a wall is not a cosmetic problem.
On plaster and texture-coated homes it is worse — high pressure lifts the coating and blows out the sealant lines around joinery. On older paintwork it strips paint you were not planning to redo.
And even where it does no damage, blasting mould only removes the visible growth. The spores and root structure stay, so it grows back within months and you conclude the wash did not work.
Which one your place needs.
It is mostly decided by the surface, not by how dirty it looks.
- Soft wash: weatherboard, plaster and texture-coat, brick, painted surfaces, cedar, soffits, fascia, spouting, joinery, roofs.
- Water blast: concrete driveways, paths, pavers, retaining walls, schist, unsealed hard surfaces.
- The green or black film on your south wall: soft wash, always. That is mould and lichen, and pressure will not kill it.
- The grime and moss on your driveway: water blast. Nothing else shifts it efficiently.
The Wānaka-specific bit.
Southern and shaded elevations here grow lichen and mould faster than most people expect, because the sun never dries them out through winter. Under the eaves and behind anything that blocks airflow is where it starts.
Timing helps too. Washing in late spring or early autumn gives the surfaces a proper chance to dry before the frosts, which matters far more here than it does further north.
What I do.
I soft wash cladding, and I water blast the hard surfaces — because they are two different jobs, not two names for one. If a house needs both, it gets both, in that order, so the driveway grime does not end up splashed back onto freshly washed boards.
It also pairs naturally with the glass. Most people book the house wash and the windows together, since the wash puts residue on the panes anyway and doing them separately means paying twice for the same set-up.
Common questions
