What pressure washing actually is
Pressure washing removes material with mechanical force — water at high PSI physically blasting dirt off a surface. It works on hard, non-porous, structurally solid materials: concrete driveways, walkways, retaining walls, and paver flatwork where the pressure is controlled enough to preserve joint sand. It's fast and effective on the right surface.
What soft washing actually is
Soft washing uses low pressure — often not much more than a garden hose — combined with a cleaning solution that breaks down algae, mildew and organic growth chemically. The solution does the work; the water just rinses. It's the correct method for siding, stucco, painted wood, roofs and anything porous or fragile.
Why the distinction matters so much
Organic growth is the key. Algae and mildew have root structures in the surface they're growing on. High pressure knocks the visible top layer off, which looks clean for about a month before it comes back — because the root structure was never killed. A soft wash solution kills it at the root, which is why results last years instead of weeks.
The damage side is more expensive. High pressure on stucco can force water behind the surface. On vinyl it drives water behind the panels, where it grows mold you can't see. On painted wood it splinters the board face and strips paint unevenly. On an asphalt shingle roof it strips the protective granules and shortens the roof's life, which is typically also what voids the manufacturer warranty.
A simple rule of thumb
If you walk on it, it can usually be pressure washed. If it's part of the building envelope — walls, roof, trim — it should be soft washed. Driveways, patios and walkways: pressure. Siding, stucco, roofs, painted surfaces: soft.
The exception worth naming is pavers. They're flatwork you walk on, but the joint sand between them washes out under high pressure, which loosens the surface and invites weeds. Pavers get controlled pressure and, ideally, re-sanding afterward.
What to ask a company before hiring them
Ask what method they'll use on your specific surfaces and why. Anyone who says they'll pressure wash your stucco or your shingle roof is telling you something useful about how the job will go. The right answer for a house is soft washing, every time.