Pressure washing looks like the most straightforward trade there is. It is water, and it is a trigger. That is exactly why so much of the damage we get called to look at was done by someone with a rented machine and an afternoon, and why the first question on any quote we write is not how dirty something is but what it is made of.
Concrete and masonry can take real pressure, and driveways, walkways and courtyards genuinely need it — oil, traffic film and algae sit in the surface rather than on it. Everything else on a typical property has a lower ceiling, and three surfaces in particular get ruined regularly.
Wood decking is the most common casualty. Hit softwood decking with a narrow tip at full pressure and it does not just clean it — it erodes the soft early wood between the grain lines and leaves the hard grain standing proud. That is called furring, it is permanent, and from then on the deck holds dirt in the grooves and feels rough underfoot. It also opens the timber up so it takes on water faster, which is the beginning of the rot that replaces the deck a few years early. A deck should be washed at low pressure with a wide fan, worked along the grain, with the cleaning done by dwell time and solution rather than by force.
Stucco and painted siding are the second. High pressure drives water through hairline cracks and behind the cladding, where it has no route out and nothing to dry it. That shows up months later as a stain bleeding through from the inside, or as blistering paint, and by then nobody connects it to the wash. It also strips paint and chalky finishes straight off. These get a soft wash: low pressure, the right solution, dwell, rinse.
Roofs are the third and the worst. A pressure washer on asphalt shingle blasts the protective granules off — those granules are the shingle's UV protection and the reason it lasts twenty years instead of five — and on tile it drives water up under the courses and straight into the underlayment. Roofs are a soft-wash job, always. The black streaking on a roof is algae, and algae dies from being treated, not from being hit hard.
There is a category of damage that has nothing to do with pressure, too. Run-off carries whatever came off the surface — oil, algae treatment, detergent — into planting beds, pool surrounds and storm drains. Anything worth covering should be covered before the machine starts, and run-off should be directed somewhere it will not kill a border or end up in the ocean.
The one thing that tells you a job is being done properly is boring: a test patch. A small area cleaned first, at the pressure and with the solution intended for the whole surface, so the result is visible and agreed before anything is committed. If nobody offers to do that, the surface is being used as the test.
Over the Top Window Cleaning pressure washes driveways, decks, patios, siding and roofs across the Harbor Area, South Bay, Palos Verdes, Los Angeles and the Westside. Free written quotes — call (310) 972-8217.