Soft wash: what it is, what it's for
Soft washing is the modern standard for cleaning anything finished — anything where the surface itself is the protective layer. The pressure is intentionally low (under 500 PSI, often closer to garden-hose pressure). The cleaning is done by chemistry, not force.
A soft-wash system delivers a biodegradable detergent (typically a sodium hypochlorite blend with a surfactant) at low pressure. The detergent dwells on the surface for 5–15 minutes, breaking down mildew, algae, oxidation, and pollen at the chemistry level. Then it's rinsed off at low pressure.
Use soft wash on:
- Vinyl, Hardie, or wood siding
- Painted exteriors (any age)
- Stucco (any age, including older Sacramento Tudor and Craftsman homes)
- Asphalt shingle roofs (ARMA-approved method)
- Tile and slate roofs
- Solar panels (pure water variant — no detergent)
- Decks, fences, and outdoor wood furniture (wood-safe detergent)
Pressure wash: when high PSI is actually right
Pressure washing — actual high-PSI work — is correct for hard, unfinished surfaces. The cleaning is done by mechanical force: physically blasting embedded dirt off the surface.
A proper pressure-washing rig uses 1,500–4,000 PSI through a surface cleaner (a 15" pressure dome that distributes the pressure evenly across the slab). This is what restores driveways, walkways, and patios to look new.
Use pressure wash on:
- Concrete driveways, walkways, and patios
- Asphalt parking lots and lots
- Brick (with caution — old mortar can be damaged)
- Stone walkways and walls
- Unfinished hardscape
- Garage floors
What happens when you use the wrong one
This is where most damage happens.
High pressure on siding: chips paint, dents soft trim, drives water behind the cladding (causes rot and mold inside the wall). Most Sacramento home damage from pressure washing happens here.
High pressure on roofs: strips the granules that protect asphalt shingles from UV. Voids most shingle warranties. The roof looks 'cleaner' for 6 months, then starts failing 5 years early.
Low pressure on concrete: leaves zebra striping — clean lines from the detergent path, dirty lines between. No real cleaning happens. The driveway looks worse than before.
Most jobs use both
A full residential property wash typically uses both methods on the same visit:
Soft wash for the house exterior and roof; pressure wash with a surface cleaner for the driveway, walkway, and front patio. Two systems on the same truck, two different surfaces, one combined quote.
If a Sacramento pressure-washing company tries to use 'pressure washing' for everything — siding included — they're not soft-washing. That's the operator to avoid.