Soft washing and pressure washing are not the same job, and using the wrong one is how render gets etched and roofs get wrecked. Soft washing uses low pressure and a biodegradable detergent to kill mould, lichen and algae on delicate surfaces like render, painted weatherboard and roofs. Pressure washing uses high-pressure water to blast dirt off hard surfaces like concrete, pavers and brick. The surface decides which one you need, not the other way around.
We do both across Melton and Melbourne’s west, and most of the damage we get called out to fix comes from someone using a pressure washer where a soft wash was the right call. Here is how to tell them apart and pick the right one for your place.
The short version:
- Render, cladding, painted timber, roofs: soft wash, always.
- Concrete, pavers, brick, driveways, tile: pressure wash.
- Green or black growth that keeps coming back: soft wash, because it kills the spores.
- Ground-in dirt and grime on hard surfaces: pressure wash.
- Not sure: match the method to the softest surface involved, or get someone to look before anyone points a lance at it.
What is the difference between soft washing and pressure washing?
The core difference is pressure. Soft washing runs at roughly garden-hose pressure (under 500 psi) and does its cleaning with detergent chemistry. Pressure washing runs at 1,500 to 4,000 psi and does its cleaning with force. One dissolves the problem, the other blasts it off, and that difference decides which surfaces each is safe on.
| Feature | Soft washing | Pressure washing |
|---|---|---|
| Water pressure | Low, under 500 psi | High, 1,500 to 4,000 psi |
| How it cleans | Biodegradable detergent kills growth | Force of water strips off dirt |
| Best surfaces | Render, cladding, paint, roofs, fences | Concrete, pavers, brick, tile, driveways |
| Kills mould and algae? | Yes, at the root | No, only removes the surface layer |
| How long results last | Longer, growth is killed off | Shorter on organic growth, it regrows |
| Risk on the wrong surface | Low | High, can etch and gouge |
Soft wash detergents are chlorine or sodium-hypochlorite based, mixed with a surfactant so they cling to the surface and soak in. That is why a soft wash looks like almost nothing is happening while it works, then the surface rinses clean. The cleaning is chemical, not mechanical.
When should you use soft washing?
Use soft washing on any surface that is painted, coated, porous or fragile, which covers most of the vertical surfaces on a house. Render, acrylic and cement cladding, painted weatherboard, Colorbond and tiled roofs, eaves, fascias and fences all fall in this camp. These surfaces hold onto mould and lichen, and high pressure either drives water behind them or strips the finish.
The bigger win with soft washing is that it lasts. Because the detergent kills the algae and lichen spores rather than just knocking off the visible layer, the surface stays clean far longer before it greens up again. According to roofing manufacturers including BlueScope, the maker of Colorbond, roofs should only ever be cleaned with low-pressure methods, because high pressure damages the protective coating and voids the finish warranty.
A render job in Fraser Rise is a good example. The north wall had gone green with mould and the owner had been scrubbing it by hand every few months. We soft washed it once, the growth died off over the following week, and eighteen months later it was still clean. Scrubbing removed the surface. The wash removed the cause.
When should you use pressure washing?
Use pressure washing on hard, non-porous surfaces where ground-in dirt is the problem, not living growth. Concrete driveways, exposed aggregate, pavers, brick paths, tiled patios and retaining walls all take high pressure well and come up sharp for it. This is where the force of the water genuinely is the right tool.
Even here, technique matters. Too much pressure held too close will etch concrete, blow the sand out of paver joints and leave wand marks that show up as stripes once the surface dries. Proper pressure washing is about the right nozzle and a consistent distance, not just maximum power. We cover what that looks like on our driveway and concrete cleaning and pressure washing pages.
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Using a pressure washer on a soft-wash surface is the single most common way people damage their own home. On render it etches the surface and can force water behind the coating. On painted weatherboard it strips the paint. On a roof it cracks tile glaze or scours the Colorbond coating, which is exactly what the manufacturer warns against.
The reverse mistake is milder but still a waste. Soft washing a heavily soiled concrete driveway will lift the mould but leave the ingrained grime, because there is no detergent that replaces the mechanical scrub a pressure washer gives concrete. Match the method to the surface and both problems disappear.
Does soft washing or pressure washing last longer?
On organic growth like mould, algae and lichen, soft washing lasts far longer, often two to three times as long as a pressure clean of the same surface. That is because pressure washing removes what you can see while leaving the spores behind, so the growth returns within months. Soft washing kills the organism, so it has to re-establish from scratch before it comes back.
On hard-surface dirt, the question does not really apply, because that grime is not alive. It comes back at whatever rate your driveway collects traffic, leaves and oil, and a pressure wash resets it each time. The rule of thumb: if the stain is green, black or patchy and keeps returning, it is biological and wants a soft wash.
Which does your house actually need?
Most homes need both, on different surfaces, which is exactly why it pays to have someone who does both look at the whole property. The walls, roof and fences want a soft wash. The driveway, paths and patio want a pressure wash. Getting it right is a matter of walking the place and matching each surface to the method that cleans it without harming it.
In Melbourne’s western suburbs this comes up constantly, because so many of the newer estates in Melton, Fraser Rise and Aintree are rendered, and render is the surface people most often damage with a hired pressure washer. When you book Outdoor Revival you deal with Michael, who will tell you honestly which surfaces need which, and there is no call-out fee to come and assess it. Have a look at the results in our before-and-after gallery to see the difference a proper wash makes.
Common questions about soft washing and pressure washing
Is soft washing safe for roofs? Yes, and it is the only safe method. Roofing manufacturers specifically require low-pressure cleaning, because high pressure strips the protective coating off Colorbond and cracks the glaze on tiles. A soft wash cleans the roof and kills the lichen without touching the coating.
Will pressure washing damage render? It can, easily. High pressure etches acrylic and cement render and can force water behind it, which leads to bubbling and staining down the track. Render should be soft washed every time.
Can you soft wash a concrete driveway? You can, and it will kill any mould, but it will not shift ingrained dirt and tyre marks the way pressure washing does. For concrete and pavers, pressure washing is the better tool.
How often should you soft wash a house? Most homes in Melbourne’s west benefit from a soft wash every 18 to 24 months, sooner on shaded or south-facing walls that green up faster. Keeping on top of it is far cheaper than letting lichen get established in the render.
