The words on the quote
Almost every company doing this kind of work in Southwest Florida says the same thing: low pressure, gentle, safe for your roof. Almost nobody puts an actual number on it. That's not an accident. "Low" doesn't mean anything on its own. It's a word, not a measurement, and it's the same word a company using 1,500 PSI on a tile roof would use too.
So here's the number. The roof never sees more than 70 PSI. That's delivered from a battery-powered pump, not a gas engine, and 70 PSI is roughly what comes out of a garden hose. No loud machine parked in the driveway, no one climbing around on the tile.
What actually removes the black and green
The growth on a Florida roof, the black streaking, the greenish film, isn't dirt sitting on top of the surface. It's organic, and pressure alone doesn't lift it, it just knocks the top layer off and leaves the rest to grow back within weeks. A cleaning solution applied at the right strength kills it at the source. Once that's done, the roof only needs a rinse, and the rinse is the part that happens at 70 PSI. The chemistry does the work. The water carries it away. That's the entire method in one sentence.
A method, not a service
This is the part almost nobody explains: soft washing isn't one job. It's the approach used across most of what gets cleaned on a house. The roof gets soft washed. So does the soffit and fascia, the pool cage screens and frame, the siding, stucco and any painted or textured exterior surface. All of it uses the same basic idea, chemistry first, low-pressure rinse second, just adjusted for what's being cleaned.
That's different from concrete, sidewalks, curbing and pavers, which is where the method changes completely.
The three numbers that matter
Roof: never more than 70 PSI, garden hose pressure, from a battery pump.
Exterior soft wash, meaning soffit, fascia, pool cage screens and home exteriors: 900 to 1200 PSI.
Concrete, sidewalks, curbing and pavers: 3000 to 4000 PSI.
The gap between those numbers isn't arbitrary. A roof tile or a screen enclosure can't take real pressure without cracking or tearing. Concrete and pavers can, and actually need it, because the growth sits down in the texture and the joints, not just on top the way it does on a smooth surface. Matching the pressure to what it's landing on is the entire idea. It's not a slogan, it's the reason the numbers are three different numbers.
Shingle, tile and metal
The method doesn't change much across roof types, which surprises people who expect tile to need something completely different from shingle. It doesn't. What changes is how much damage the wrong approach would do.
Shingle roofs lose granules under real pressure, and those granules are the part doing the actual protecting. Once they're blasted off, they don't come back. Tile is the opposite problem: the tile itself handles weather fine, but it cracks under the weight of someone walking on it, so the risk isn't the water, it's the person. Metal roofs are the most forgiving of the three, though the coating on them isn't something worth testing against high pressure either.
In all three cases the answer is the same: treat the growth with chemistry, rinse at low pressure from the ground, and nobody needs to be up there at all. That's why the legacy approach of writing a separate playbook for each roof material was always a bit beside the point.
Why this matters more than it sounds like it should
If a company won't tell you what pressure they're using on your roof, that's worth noticing. "Low pressure" that turns out to mean 1,000 PSI on tile is still enough to crack it, especially with someone walking around up there to apply it. A soft wash roof job doesn't need anyone on the roof at all, because the pump and the hose reach it from the ground.
What about the landscaping
If the chemistry is doing the work, the obvious next question is what happens to whatever the rinse water lands on. Short version: the solution gets diluted down for what it's landing near, and your own irrigation, run before the job and for a week to 10 days after, flushes anything that reaches the soil back out. That's the part most companies skip explaining, and it's the difference between a yard that's fine afterward and one that isn't. It's worth understanding before you book anything, not after.
What this means for your job
If it's a roof, expect 70 PSI and nobody walking the tile. If it's the exterior of the house, the soffit, the pool cage, expect that same chemistry-first approach at 900 to 1200 PSI, still well short of what a concrete surface gets. And if your driveway or pavers need attention too, that's a different job entirely, at a different pressure, because that surface is built for it.
Common questions
Is soft washing just a nicer word for pressure washing?
No. It's a different method, not a different label for the same one. Pressure washing cleans with force. Soft washing cleans with a solution and uses low-pressure water only to rinse. The 70 PSI number is what makes the difference concrete instead of a marketing word.
Does anyone need to walk on my roof?
No. Both the solution and the rinse reach the roof from the ground. That matters most on tile, where the weight of a person is a bigger risk to the roof than anything the water does.
Will it damage my shingles?
At 70 PSI there isn't enough force to strip granules, which is the actual damage mechanism people worry about. That's the whole reason the number is that low.
Get a number for your job
Text a few photos of whatever needs the work, roof, walls, pool cage, and pricing comes back the same way. No one has to walk the property first to give you a real number.