They are two different tools for two different problems, and the choice is dictated by the surface, not by preference. Pressure washing uses force to remove what is sitting on a surface. Soft washing uses low pressure and cleaning solution to kill what is growing in it.
On a Brisbane home you almost certainly need both — pressure for the driveway and paths, soft washing for the roof and walls. Using the wrong one is how people end up with stripped render, water in the ceiling, or a house that looks clean for six weeks and then goes green again.
What each one actually is
Pressure washing is mechanical. High-pressure water does the work, blasting dirt, moss and surface grime off hard, dense materials. On concrete this is exactly right — the surface is tough enough to take it, and the dirt is genuinely sitting on top.
Soft washing is chemical. Pressure is dropped to roughly garden-hose level and a cleaning solution does the work instead. It is applied, left to dwell, then rinsed. The solution kills mould, algae and lichen at the root rather than removing the visible layer.
The distinction that matters: pressure removes growth, chemistry kills it. That is why the results last such different lengths of time.
Why this matters more here than in most places
Brisbane’s subtropical climate means most of what discolours a house is alive. The green film on a shaded wall, the black streaking on a roof, the patchy dark growth on the south side — these are organisms with roots into the surface, not dirt lying on it.
Blast that with pressure and you remove the visible part. The root structure stays, and in a humid climate it regrows quickly. Treat it with the right solution and the organism dies, so regrowth starts from spores rather than from an established colony — which takes considerably longer.
This is the single most common reason people feel their house wash “didn’t last”.
Which surface needs which
Soft wash:
- Roofs — almost always. Pressure on tiles can break them, force water under the laps into the roof cavity, and strip the bedding and pointing around ridge caps. It also puts a person walking on tiles that may already be brittle. Repairing that costs many times the price of the clean.
- Render, painted weatherboard and cladding. Pressure lifts paint, drives water behind boards and etches render.
- Anything with seals or penetrations — windows, vents, eaves.
Pressure wash:
- Concrete driveways, paths and slabs. Dense, tough, and usually genuinely dirty rather than biologically stained.
- Brick paving and retaining walls, at sensible pressure.
- Hard surfaces with ingrained traffic grime, where the dirt is mechanical rather than living.
Plenty of jobs are mixed. A driveway with mould in the shaded section often wants a chemical treatment first and pressure second — which is really the same principle applied in order. We go into that in more detail in removing mould from concrete.
What going wrong looks like
- Tile damage and leaks. Cracked tiles are obvious. Water forced under laps is not — it shows up as a ceiling stain weeks later, long after anyone connects it to the clean.
- Lap marks on render. Uneven pressure leaves visible stripes that do not weather out.
- Stripped paint. Easy to do on older weatherboard, and it turns a wash into a repaint.
- Concrete etching. Holding a turbo nozzle too close leaves permanent wand marks in the surface.
- Fast regrowth. The subtle one. If growth returns within a couple of months, it was almost certainly removed rather than killed.
What to ask before anyone starts
Three questions separate a considered contractor from someone with a wand and a trailer:
- Which method will you use on each surface, and why? A clear answer that differs by surface is a good sign. “We pressure wash everything” is not.
- What are you putting on my roof, and what happens to the runoff? Solutions end up in garden beds and stormwater. It is reasonable to ask how that is managed.
- What do you expect this to look like in six months? Anyone who has actually killed the growth will happily talk about longevity. Anyone who has only stripped it will change the subject.
The short version
If it is hard, flat and dirty, pressure is usually right. If it is fragile, painted, up high, or green — chemistry is right. Most homes need both, applied to the correct surfaces, and the difference between a wash that lasts a season and one that lasts years is almost always this decision rather than the equipment.
If you are unsure which your place needs, read what external house cleaning involves, or request a free quote and we will tell you which method suits each surface before we quote it — including where a soft wash would be a waste of your money.
