People call it all pressure washing, but there are really two jobs. Pressure washing uses the force of the water — 2,500 to 4,000 PSI through a surface cleaner or a wand — to scrub a hard surface. Soft washing uses low pressure, about what a strong garden hose puts out, and lets a cleaning solution do the work instead. Knowing which one a surface needs is most of what separates a professional from someone with a rented machine.
Pressure washing is for hard, durable surfaces: concrete, pavers, brick, block, natural stone, asphalt, metal. These take high pressure without damage, and on flat concrete a rotary surface cleaner at high pressure is the only way to get an even, stripe-free finish. Driveways, sidewalks, parking lots, garage floors, patios, retaining walls and dumpster pads are all pressure-washing jobs.
Soft washing is for everything that high pressure would damage: stucco, painted siding, fiber-cement and vinyl siding, wood, EIFS, roofs, screens, and anything with a coating. High pressure on stucco pits it and blows out the finish coat; on lap siding it forces water up behind the laps and into the wall; on paint it lifts and chips; on wood it furs the grain and leaves permanent wand marks. A soft wash applies a solution that kills the algae and mildew and loosens the dirt, waits, and rinses at low pressure. The wall comes clean, and the algae stays gone longer because the solution killed it rather than just knocking it off.
Most buildings need both. A typical Peninsula commercial building gets a soft wash on the stucco and painted surfaces, pressure on the concrete entry and the sidewalk, and something in between on the block or brick base. A house is the same: soft wash on the siding and trim, pressure on the driveway, walk and patio, low-pressure wide fan on the deck and fence. The person doing the work has to change methods as they move around the building.
The signs someone used the wrong one. Stripes or 'tiger marks' on a wall or a deck mean a wand was used at high pressure and too close. Pitted stucco, lifted paint and raised wood grain are the same story. Water stains inside a wall a week after a wash mean siding was blasted and water got behind it. None of that comes out; it has to be repainted or replaced. The cheapest wash isn't cheap if it costs a paint job.
What we do. We look at each surface on the property and assign it a method before we start — pressure and a surface cleaner for the flatwork, a soft wash for anything sided, stuccoed or painted, low pressure along the grain for wood. We protect windows, fixtures and landscaping, rinse top-down so dirt runs off clean walls instead of down them, and finish with the concrete below so the building isn't standing on a dirty pad.
If you're not sure what your building needs, that's fine — that's the estimate. Call or text AQ Professional Power Washing & Striping at (650) 274-6797, send a couple of photos, and we'll tell you what each surface gets and what it costs. We work across San Mateo, Burlingame, Redwood City, Menlo Park and the Peninsula, 5am to 11pm, seven days.