Why most roof pressure washing goes wrong (and how mine doesn't)
The Asphalt Roofing Manufacturers Association's guidance is worth knowing: a standard pressure washer runs 2,500 to 4,000 PSI, and shingles can only handle roughly 100 to 200 PSI before they start losing granules — the protective coating that keeps them from breaking down in the sun. That's exactly what happens when someone points a rental-grade or DIY pressure washer at a roof with no experience behind it. Strip enough granules and you're not looking at a cleaner roof, you're looking at a roof that fails years earlier than it should have.
That's a real risk, but it's a technique problem, not a reason to rule out pressure washing altogether. Done at the right pressure, with the right nozzle and the patience to read what a specific roof can take, roof pressure washing gets the job done without stripping anything. Depending on what your roof actually needs, I'll use a soft wash treatment — a diluted cleaning solution applied at low pressure — or careful, controlled pressure washing kept well inside the range your shingles can handle. Same result either way: a clean roof with the granule coating still intact.
Moss vs. algae — they're not the same problem
Those black streaks on a lot of South Sound roofs are algae, and here's the honest truth: it's cosmetic. The roofing industry's own research says there's no evidence algae actually damages the shingles — it just makes the roof look older than it is.
Moss is a different story. It holds moisture against the shingle surface and grows up under the shingle edges, which can lift and curl them. That raises real risk of wind damage and leaks, not just an appearance issue. If you've got moss, that's worth addressing sooner rather than later.
What a proper cleaning includes
A soft wash treatment or controlled pressure washing — whichever fits your roof — plus a look at the roofline while I'm up there, checking for anything that needs more than a cleaning, like lifted shingles or gutter issues. Same climate-appropriate approach whether you're dealing with algae streaking or moss buildup.
What it costs
Soft wash roof cleaning in this area typically runs $300 to $800 for a standard residential roof, depending on size, pitch, and how much moss or algae buildup there is. You'll get a real number after I've actually looked at your roof, not a guess over the phone.
Service area
Based in Roy, WA, serving Pierce County, Thurston County, and nearby South Sound communities including Auburn, Bonney Lake, Buckley, DuPont, Eatonville, Edgewood, Fife, Fircrest, Gig Harbor, Lakewood, Lacey, Milton, Olympia, Orting, Pacific, Puyallup, Spanaway, Steilacoom, Sumner, Tacoma, Tumwater, University Place, Yelm, and surrounding areas. Not sure if your address is covered? Just ask.
Pairs well with
Roof cleaning is a natural pairing with gutter cleaning, since the debris causing roof staining usually ends up in the gutters too. It's also a good time to check the fascia for signs of water damage while the whole roofline's already getting a look.
Frequently Asked Questions
Will pressure washing damage my roof? Only if it's done wrong. Most roof damage comes from a standard pressure washer run at full pressure — 2,500-4,000 PSI — on shingles rated for a fraction of that. I keep the pressure well within a safe range and use the right technique, so it doesn't happen. If your roof calls for it instead, I'll use a soft wash treatment.
Are those black streaks on my roof dangerous? No, they're algae, which is cosmetic. Moss is the one to watch — it can lift shingle edges and lead to real damage, not just a look.
How often does a roof need cleaning? Depends on tree coverage and shade, but most South Sound homes benefit from a check every year or two given how much moss our climate grows.
How much does roof cleaning cost? Typically $300-800 depending on size and buildup. You'll get a specific number after a free, in-person look.
Is the estimate really free? Yes, no obligation to book.
