Serving the Seattle Eastside
Roof Washing
Roof Washing for Eastside homes — kills moss and Gloeocapsa magma at the root, never pressure washed. Licensed, Bonded, and Insured.
Moss on an asphalt roof is not a cosmetic issue. The root systems — called rhizoids — penetrate the surface of the shingle and physically lift the granules away from the mat. Once those granules are gone, UV damage accelerates rapidly. A roof with active moss growth is a roof that is aging faster than it should. Most roofing manufacturers in the Pacific Northwest void the warranty on roofs with untreated biological growth, because they know what we know: moss is a slow demolition crew working on your behalf.
Why Eastside Homeowners Choose PNW Softwash for Roof Washing
We use a low-pressure soft wash system — never a pressure washer on a roof. High pressure washing blows granules off the shingles and voids manufacturer warranties. Our biodegradable sodium hypochlorite solution kills moss, algae, lichen, and the black algae streaks (Gloeocapsa magma) at the biological level, not just at the surface. Dead moss dries and sheds naturally over the following 4–8 weeks, leaving a clean roof without the scraping and raking that damages shingles.
We treat every roof with a post-wash zinc or copper sulfate rinse to inhibit regrowth. Combined with the soft wash treatment, this extends the clean period significantly compared to a rinse-only approach.
The Difference Is Visible
Real results from homes across the Eastside.
Roof Wash — Issaquah Highlands
Roof Wash — Klahanie
Cedar Shake — Sahalee
Drag the handle to reveal the transformation. Real homes, real results.
What Our Roof Washing Service Includes
Our roof washing process: pre-wet all landscaping and downspouts to protect from runoff, apply soft wash solution at low pressure from ground or ladder (no walking the roof), dwell for 15–20 minutes, rinse with clean water, apply post-wash anti-regrowth treatment, remove all protective covers.
We carry full liability insurance specifically for roof work. Every technician is trained in manufacturer-safe soft wash protocols. We don't walk roofs on pitches over 6:12 without safety equipment — and we have it.
Pricing for a typical single-story home (1,800–2,400 sq ft footprint) starts at $500–$750. Two-story or steep-pitch roofs run $750–$1,200+. We quote based on roof square footage and pitch — you'll have a firm number before we start.
What Homeowners Say
★★★★★
“Oh my goodness! PNW Softwash did such an amazing job on our roof and gutters. They even cleaned our chimney and made it look like new. That was an exciting bonus. The appointment was easy to book, and I was able to get them here quickly on my schedule. Their prices are extremely competitive. They arrived on time, were very professional, communicated well and cleaned up before they left. I really couldn't be happier. Their soft wash gently cleaned our roof and they've added years to it's life. I highly recommend.”
— K King
Roof Washing — Every City We Serve
Select your city for local pricing, neighborhood-specific details, and free same-day quotes.
Roof Washing — Frequently Asked Questions
Honest answers from a Licensed, Bonded, and Insured crew that works on the Eastside every week.
How much does roof soft washing cost in King County?
- Roof soft washing in the King County area typically runs $500–$1,200, with large or complex rooflines up to $2,500, depending on your roof's size, material type, and the extent of moss or algae growth. We provide free, no-obligation assessments — we'll look at your roof, explain what it needs, and give you a clear quote with no hidden fees. Compare that to $15,000–$30,000 for premature roof replacement, and the math is clear.
Will soft washing void my roof warranty?
- No — in fact, most roofing manufacturers specifically recommend low-pressure cleaning and prohibit pressure washing. Soft washing preserves your shingle granules and protective coatings, maintaining your manufacturer's warranty. Pressure washing, on the other hand, can void your warranty because of the damage it causes.
How long will the results last?
- Soft washing results outlast pressure washing 3–5 times longer, because we treat the organics — not just the surface. Roof treatments typically hold for 2–3 years. House washing lasts 2–3 years. Concrete results vary by shade and foot traffic. Trash can cleaning works best as a continuous maintenance program — once clean, we keep it that way. There are variables such as North-facing roofs/walls, tree coverage, and weather exposure that uniquely affect each home. We are here to help. Get your free quote today.
What is soft washing and how is it different from pressure washing?
- Soft washing uses low-pressure water (165 PSI — your garden hose is about 40–80 PSI) combined with specialized, biodegradable cleaning solutions that kill moss, algae, and organic growth at the root level. Pressure washing blasts surfaces with 2,000–4,000 PSI. For roofs, pressure washing strips protective granules from shingles, forces water underneath, and can void your warranty. Soft washing preserves your roof while delivering results that last 3–5 times longer.
What are the black streaks on my roof and how long before they return after cleaning?
- Those black streaks are a blue-green algae called Gloeocapsa magma that feeds on the limestone filler in your shingles. It's not dirt — it's literally eating your roof. Our Pacific Northwest climate of rain, shade, and moisture creates ideal conditions for this algae. Professional soft washing kills it at the cellular level and prevents it from coming back for 2–3 years.
Ready to Book Roof Washing?
Free same-day quotes. Serving the entire Seattle Eastside.