Guide
Soft wash vs pressure wash: it depends on the surface, not the dirt
Pressure washing removes dirt by force. Soft washing removes it with chemistry and time, at about the pressure of a garden hose. Neither is better in general. Concrete takes force and benefits from it. Paint, render, weatherboard, tiles and timber do not, and blasting them causes the damage people later blame on “pressure cleaning”.
The table below is the one we work from. Find your surface and the method is next to it, with the reason.
Surface by surface
| Surface | Method | Why |
|---|---|---|
| Render and painted walls | Soft wash | Pressure lifts paint at any weak edge. |
| Weatherboard and cladding | Soft wash | Pressure drives water up behind the laps. |
| Concrete and terracotta tile roofs | Soft wash only | Pressure pushes water between tiles and into the ceiling. |
| Colorbond and metal roofs | Soft wash | The coating protects the steel and pressure strips it. |
| Timber decks | Soft clean | Pressure raises the grain and furs the boards. |
| Plain concrete driveways and paths | Pressure wash | Dense, hard wearing and built to take it, used with a surface cleaner and sense. |
| Oil, grease and chewing gum on concrete | Hot water pressure | Heat dissolves and softens what cold water pushes around. |
| Pavers | Pressure, carefully | The joint sand washes out and has to go back in. |
| Fibro and cement sheet | Neither | Asbestos risk. SafeWork NSW prohibits high pressure on it, and we do not soft wash it either. |
Why soft washing lasts
Mould, algae and lichen are alive and rooted into the surface. Pressure knocks off what it can see and leaves the root, which is why a blasted wall greens up again quickly. A soft wash solution kills the growth where it sits, then the rinse carries it away.
Where pressure earns its place
Dense concrete, stuck on grime and anything that has soaked in. A rotary surface cleaner held at the right height cleans a driveway evenly. A bare wand held close to the same driveway is how the stripes get there.
And where heat does
Oil, grease and chewing gum. Kärcher, Spitwater and Aussie Pumps all describe hot water as faster and more effective on those. None of them calls it required, and neither do we. We call it the right tool for those jobs.
How it shows up on our prices
The method is not a separate line. A single storey house is soft washed for $549, and oil, grease and hydrocarbon cleaning with hot water starts from $280 up to 30 square metres, both including GST. Neither carries a surcharge for the method, because the surface decides the method and you should not pay extra for the right one.
Soft wash and pressure wash questions
What is the difference between soft washing and pressure washing?
Pressure washing uses force to remove dirt. Soft washing uses low pressure and a cleaning solution left to work, so the growth dies and rinses off. Pressure suits hard, dense surfaces like concrete. Soft washing suits anything with a coating, a lap or a gap.
Does pressure washing damage concrete?
It can. A narrow jet held too close, or too much pressure on a weak or old surface, etches the top and leaves stripes or wand marks. Sound concrete cleaned at the right distance, ideally with a rotary surface cleaner, takes it well. Exposed aggregate and sealed surfaces need more care than plain broom finish.
Can you pressure wash a roof?
Not a tile roof, not if you want a dry ceiling afterwards. Pressure drives water between the tiles, and on a roof with no sarking it goes straight through. Metal roofs can take more, but pressure strips the coating that protects the steel. Both are soft washed here.
Is soft washing more expensive?
The published evidence disagrees. One Sydney operator's method by method rate card prices soft washing above high pressure, and one national aggregator says it is slightly cheaper. On our card the method is not a separate charge: the price is for the job, and the job is done the way the surface needs.
Is hot water the same as soft washing?
No. Hot water is high pressure with heat added, and it is for oil, grease and gum on hard surfaces. Equipment makers describe it as faster and more effective on those, not as required. It is the wrong tool for a tile roof or a painted wall.
Does soft washing need more water rules than pressure washing?
The same ones. Washing a building is permitted under Sydney Water's Water Wise Guidelines at any time. A driveway needs a listed reason such as safety or contamination. Either way, the wash water is kept out of the stormwater drain.