Guide
Soft wash vs pressure washing.
They are different jobs done with the same machine. Knowing which one your house needs is the difference between a clean exterior and an expensive repair.
The short version
Pressure washing cleans mechanically. Water at high pressure blasts material off a surface. It is the right answer for concrete and almost nothing else on a typical Florida home.
Soft washing cleans chemically. A cleaning solution is applied at low pressure, left to dwell so it kills the organic growth at the root, then rinsed off. The water is a delivery and removal system, not the cleaning agent.
The test that matters: is the thing on the surface alive? Mildew, algae, lichen and the black roof streaking are all living organisms. Blasting them removes the visible layer and leaves the roots, and it comes back in a season. Killing them chemically keeps it clean for years.
Why high pressure causes damage
A pressure washer capable of stripping paint is capable of stripping your paint. The common failures in this county, in order of how often they turn up:
- Water behind vinyl siding. Panels are designed to shed water running down, not water driven upward at 3,000 PSI. What gets behind them stays there.
- Shingle granule loss. Granules are the roof's UV protection. Removing them buys a clean roof at the cost of years of roof life.
- Furred timber. High pressure carves the soft growth rings out of pine and cedar, leaving a fuzzy surface that then holds dirt worse than before.
- Etched and striped concrete. Overlapping wand passes leave permanent lap marks in the surface.
- Blown screen panels. A screen enclosure will lose its spline long before it loses its dirt.
What gets which
| Surface | Method |
|---|---|
| Vinyl siding | Soft wash |
| Stucco, painted or bare | Soft wash |
| Fibre cement (Hardie) | Soft wash |
| Painted timber | Soft wash, gentlest setting |
| Asphalt shingle roof | Soft wash, zero pressure |
| Concrete or clay tile roof | Soft wash, zero pressure |
| Screen enclosure | Soft wash, very low |
| Composite decking | Soft wash |
| Concrete driveway or walkway | Pressure, surface cleaner |
| Brick and block | Soft wash, moderate rinse |
| Pavers | Pressure, then re-sand |
How to check what you are being sold
Ask one question: what pressure will be at the wall, and what are you putting on it? Anyone who answers by naming the PSI of their machine rather than the pressure at the surface is describing equipment, not method. The number that matters is the one where the water lands.