Soft Wash vs Pressure Wash (And Why It Matters)
If someone aims a 3,500 PSI pressure washer at your vinyl siding, they can blow the seams apart, force water behind the house wrap, and leave you with a mold problem worse than what you started with. This is why soft washing exists.
What pressure washing actually is
Pressure washing uses high-pressure water (2,500 to 4,000 PSI at the nozzle) to blast dirt, oil, and grime off hard surfaces. It's great for concrete driveways, brick walkways, pool decks, and heavy commercial surfaces that can take the force.
Pressure alone doesn't kill mold or algae. It knocks the top layer off, but anything with roots (which is most organic growth on Long Island) grows right back within 3 to 6 months.
What soft washing actually is
Soft washing is low-pressure (under 500 PSI, roughly a garden hose) combined with a biocide solution (sodium hypochlorite + surfactant) that kills mold, mildew, and algae at the root. The chemistry does the work, not the water pressure.
On Long Island homes — vinyl siding, cedar shingles, stucco, painted wood, roofs — soft washing is the only right answer. PWNA guidelines and every major siding manufacturer (CertainTeed, James Hardie, Mastic) explicitly require soft wash for warranty compliance.
How to tell which your contractor is doing
Ask to see the tip. A soft wash tip is a wide black nozzle with very low pressure; a pressure tip is a tight red, yellow, or green nozzle with tight spray. If they're running a 0-degree or 15-degree tip on your siding, walk them off the property.
Ask what's in the mix. A legitimate soft wash contractor will say sodium hypochlorite, surfactant, and water — diluted to roughly 1 to 3 percent on siding. If they say "just water" or "proprietary secret," they're either guessing or cutting corners.
When pressure washing is right
Concrete driveways and sidewalks, brick pavers, pool decks, fences that are structurally sound, dumpster pads, parking lots, fleet trucks. Anything flat and hard that's engineered to take force.
When soft washing is right
Vinyl siding, cedar shake, HardiePlank, stucco, painted wood, asphalt shingle roofs, screened enclosures, pool cages, awnings, and anything with an organic mold or algae problem. Which, on Long Island, is almost everything facing north.