Soft washing uses a cleaning solution at under 500 PSI to kill algae and mildew at the root. Pressure washing uses water force — typically 3,000 to 3,500 PSI — to blast contamination off. Siding, stucco, painted wood and roofs need soft washing. Concrete, brick paving and masonry need pressure washing. Getting it the wrong way round either damages your house or gives you a clean that lasts eight weeks.
Below: what actually separates the two methods, a surface-by-surface table, what's in the solution, how long each result lasts, and the specific damage high pressure does.
The actual difference
The confusion comes from thinking these are two settings on the same machine. They aren't — they're two different theories of how to clean.
Pressure washing is mechanical. Water at high velocity knocks material off a surface. It's excellent at what it's good at: embedded dirt in the pores of concrete, tyre marks, clay, general grime on hard masonry. Nothing chemical shifts embedded dirt from concrete better than a rotary surface cleaner.
Soft washing is chemical. A dilute cleaning solution is applied at garden-hose pressure, left to dwell for five to ten minutes, then rinsed away. The water never does the cleaning — it just delivers the solution and carries the dead growth off.
That distinction matters because most of what makes a Florida house look dirty is alive. The green film and black streaking are algae, mildew and bacteria with root structures sitting in the pores of your stucco or the texture of your vinyl. Force removes the visible part and leaves the roots behind.
Which surface needs which
The rule of thumb: if you could dent it, scratch it, or force water behind it, it gets soft washed. If it's poured, laid or bedded in mortar, it gets pressure.
| Surface | Method | Pressure | Why |
|---|---|---|---|
| Vinyl siding | Soft wash | Under 500 PSI | Pressure forces water behind the panels |
| Stucco / Dryvit | Soft wash | Under 300 PSI | Cracks the finish, water enters the wall |
| Asphalt shingle roof | Soft wash | Under 100 PSI | Strips granules, voids the warranty |
| Painted wood | Soft wash | Under 300 PSI | Strips the coating, raises the grain |
| Screen enclosure | Soft wash | Low rinse only | Stretches or tears the mesh |
| Concrete driveway | Pressure | 3,000–3,500 PSI | Embedded dirt needs mechanical removal |
| Brick pavers | Pressure (moderate) | 2,000–3,000 PSI | Too high blows out the joint sand |
| Timber deck | Both — chemical, low rinse | 500–800 PSI | High pressure furs the grain |
| Brick wall | Soft wash | Under 800 PSI | Old mortar joints erode |
What's actually in the solution
No mystery here, and any company that won't tell you is a company to avoid. A soft wash solution is two things:
- Sodium hypochlorite, diluted to roughly 1–3% at the surface. It's the same active ingredient as household bleach, at a similar or lower strength once it reaches your wall. It kills the algae, mildew and bacteria.
- A surfactant — a soap. This does two jobs: it breaks surface tension so the solution penetrates rather than beading, and it thickens the mix so it clings to a vertical wall long enough to work instead of running straight to the ground.
Mix strength changes by substrate. Brick tolerates 2–3%; painted wood and chalking aluminium want 1% and no more. A crew running one strength across a whole mixed-material Mandarin home will either fail to clean the brick or damage the paint.
The safety question people ask is about plants, and the answer is pre-wetting. Soaking planting with clean water before you start means the diluted solution can't be absorbed — the pore space is already full. Rinse again afterwards and it's a non-issue. Skipping the pre-wet is what kills shrubs, not the chemical itself.
How long each one lasts
This is the number that should decide it for you, because it changes the real cost per year by a factor of six.
| Method | Open, sunny lot | Shaded or coastal | Effective cost/year |
|---|---|---|---|
| Soft wash | 24 months | 12 months | $150 – $350 |
| Pressure only | 3 months | 6–8 weeks | $800 – $1,600 |
A pressure-only wash is genuinely cheaper on the day. Over three years it costs several times more, and that's before you count any damage. Our Jacksonville pricing guide has the full per-service numbers.
What goes wrong when you use pressure
These aren't hypotheticals — they're the repair jobs we get called to look at, in rough order of how often we see them.
- Water behind vinyl siding. Vinyl is designed to shed water running down it, not water driven up under the laps. Once it's in the wall cavity it feeds mould inside the house.
- Granule loss on shingles. The coloured granules are the UV shield. Strip them and the asphalt underneath bakes, becomes brittle and fails years early. Check the gutters after a pressure-washed roof — they'll be full of grit.
- Cracked stucco. Hairline cracks open under pressure and let water into the EIFS layer, which is a far more expensive problem than a dirty wall.
- Blown window seals. Pressure directed at a double-glazed unit breaks the gasket, and you get permanent fogging between the panes.
- Furred timber. High pressure tears out the soft spring wood between the grain lines. No stain hides it and sanding rarely fully recovers it — see our deck and fence guide.
- Etched concrete. Ironically the one surface that should get pressure still gets damaged by lingering in one spot. That produces the dark patches people ask about afterwards.
My honest take
The industry has made this more complicated than it is, mostly because "soft wash" sounds like an upsell. It isn't. It's just the correct method for anything that isn't concrete, and a company that soft washes your siding isn't doing you a favour — it's doing the job properly.
Where I'd push back on my own industry: soft washing is not better for everything. We get asked to soft wash driveways because people have read that pressure is dangerous, and it's a waste of money. Chemistry alone won't lift embedded dirt out of concrete. You'll get a driveway that's algae-free and still grey and dirty. Use the surface cleaner.
The one-line test that never fails: is what's making it dirty alive, or is it embedded? Alive means chemistry. Embedded means pressure. Almost everything follows from that.
If you want someone to look at your specific surfaces and tell you which is which, send us a couple of photos. Or read up on the two services directly: house soft washing and driveway pressure cleaning.
