Roof Pressure Washing vs Soft Washing: What Actually Works on a Metro Atlanta Roof
A lot of people search for roof pressure washing or roof power washing, book it, and end up with a shorter roof life and the same streaks a year later. Here is what each method actually does to a roof, and which one you want.
Every week someone in Marietta, Alpharetta or Smyrna types "roof pressure washing near me" into Google, because that is the name most people know for cleaning an outdoor surface. On a driveway, that name is correct. On a roof, it is the wrong tool, and the difference costs real money. This is the straight version of what I tell homeowners on the phone.
The short answer
A shingle roof should never be pressure washed. The force that lifts grime off concrete also lifts the protective granules off an asphalt shingle, which shortens the roof's life and voids most manufacturer warranties. What a roof needs is a soft wash: a cleaning solution applied at zero PSI that kills the algae, moss and lichen and is then rinsed away. The Asphalt Roofing Manufacturers Association endorses zero-pressure soft-wash chemistry as the safe method for cleaning shingle roofs. That is the whole reason our roof cleaning services in metro Atlanta are built around it.
What pressure washing does to a roof
A pressure washer is a blunt instrument. It works by force, and on a hard surface like a driveway, a patio or a brick walk, force is exactly what you want. Those surfaces are built to take it. An asphalt shingle is not. The shingle's top layer is a bed of ceramic granules glued to an asphalt base, and those granules are what shield the asphalt from UV. Drive water at them under pressure and they let go. You can see the result in the gutters afterward: a layer of grit that used to be the roof.
Three things follow from that. The shingle ages faster once the granules are gone. Most shingle manufacturers void the warranty when a roof has been pressure washed. And the roof does not even stay clean, because pressure only rinses the visible algae off the surface and leaves the spore base behind. The streaks come back within a season, and the next crew gets to strip another layer of granules off to chase them.
Power washing is the same thing with heated water. The heat is a real advantage on grease and oil on concrete. On a roof it changes nothing about the problem, because the problem is the pressure, not the temperature.
What soft washing does instead
A soft wash flips the method. Instead of force, it uses chemistry. A sodium-hypochlorite-based solution goes onto the roof at zero PSI, so nothing makes mechanical contact with the shingle and no granules are stripped off. The solution kills gloeocapsa magma (the black streaks), moss and lichen at the spore level, and a rinse carries it away. Because the organism is killed rather than rinsed, regrowth has to start from nothing. That difference is why we back every roof cleaning with a 3-year warranty against algae and moss re-growth, and why most metro Atlanta roofs only need it every 24 to 36 months.
The visit itself is simple. The crew tarps the landscaping under the roofline, pre-rinses, applies the solution at zero pressure, lets it work, and rinses. The solution is biodegradable. The same zero-pressure method works on asphalt shingle, metal and tile, residential and small commercial, and if there is a solar array up there we clean it in the same visit with deionized water. More on that on the solar panel cleaning page.
Side by side
| On a shingle roof | Pressure washing | Soft washing |
|---|---|---|
| How it cleans | Force | Chemistry at zero PSI |
| Granule loss | Yes | None |
| Shingle warranty | Voided by most manufacturers | Intact, ARMA-approved method |
| Black streaks | Rinsed off, spores stay | Killed at the spore level |
| How long it lasts | Often streaked again within a season | 24 to 36 months, 3-year re-growth warranty |
Pressure washing has its place. That place is concrete, hardscape and other hard surfaces, not the roof.
How to tell which one you are being quoted
Companies do not always use these words carefully, and "roof pressure washing" is sometimes just the phrase on the truck. So ask two questions. First: what pressure does the solution go on at? The right answer is zero. Second: what happens to my shingle warranty? The right answer is nothing. If the answer to either one involves a surface cleaner, a turbo nozzle or "low pressure" that still means a pressure washer on the roof, that is pressure washing under a different name. If a company is quoting you a pressure wash for your roof, ask what happens to your warranty before you say yes.
The same answer in Marietta, Alpharetta, Smyrna and Lawrenceville
The searches come from all over the north side of Atlanta and the method does not change by zip code. Asphalt shingle is the most common roof in every one of our 22 service areas, and gloeocapsa magma feeds on it the same way under an oak canopy in East Cobb as it does on a newer street in Alpharetta. Soft wash is the answer on all of them. City pages, if you want the local detail: roof cleaning in Marietta, roof cleaning in Alpharetta, Smyrna and Lawrenceville.
Common questions
Can you pressure wash a shingle roof?
Not without damage. High pressure drives the protective granules off the shingle surface, which shortens the life of the roof and voids most shingle manufacturer warranties. The Asphalt Roofing Manufacturers Association endorses zero-pressure soft-wash chemistry as the safe method for cleaning shingle roofs, and that is the only method we use on a roof.
What is the difference between roof pressure washing and roof power washing?
They are the same machine and the same pressure range; power washing adds heated water. Heat helps on grease and oil on a driveway. It does nothing to change the problem on a roof, which is that the force itself strips granules. Neither one belongs on shingles.
Does pressure washing get rid of the black streaks?
It rinses the visible algae off and leaves the spore base in place, so the roof streaks again within a season. The black streaks are gloeocapsa magma, a living algae that feeds on the limestone filler in the shingle. Soft washing kills it at the spore level, which is why regrowth has to start from nothing and why our warranty runs three years instead of three months.
Is soft washing more expensive than pressure washing a roof?
Every roof is quoted on its own size, pitch and access. On our pricing page a standard residential roof is a custom quote and multi-story or steep-pitch roofs start at $1,200, with a 3-year re-growth warranty included. A pressure wash that strips granules and comes back streaked next year is the expensive option, whatever it costs on the day.
How do I know which method a company is quoting me?
Ask two questions: what pressure does the solution go on at, and what happens to my shingle warranty. The right answer to the first is zero PSI, and the right answer to the second is nothing. If the answer involves a surface cleaner or a turbo nozzle on the roof, that is pressure washing with a different name.
Do you soft wash roofs in Marietta, Alpharetta, Smyrna and Lawrenceville?
Yes. The same ARMA-approved zero-pressure method covers all 22 of our metro Atlanta service areas, on asphalt shingle, metal and tile roofs. The crew tarps the landscaping, pre-rinses, applies the biodegradable solution at zero pressure, lets it work, and rinses.
Want the deeper reading? Why the streaks show up in the first place: why does my roof have black streaks? How the method earns the ARMA name: what ARMA-approved roof cleaning means. The same question for the rest of the house: pressure wash vs soft wash. And the full service page, with every question we get about the method, timing and warranty: roof cleaning services in metro Atlanta.
Ready to have the roof looked at? Text us a couple of photos and we will send a free, honest quote.
More guides from the crew on the Sunshine blog.