What's actually included in professional roof washing services, soft wash vs. pressure wash, real pricing, and how often you need it — straight from a Snohomish County crew that does this every week.
Professional roof washing services use a soft-wash method — low-pressure water plus a cleaning solution — to kill moss, algae, and lichen without damaging shingles, and most include a debris blow-off, the wash itself, and a post-job inspection. At Xzavier's, a standard treatment runs $450–$649 depending on roof condition.
Full disclosure: no kid draws "roof-moss consultant" on career day. But somebody has to explain why your shingles look like a Jurassic diorama, and today that somebody is us.
What Do Roof Washing Services Actually Include?
A proper roof washing service covers three stages: clearing loose debris so the cleaning solution can reach the surface, applying a low-pressure soft-wash treatment to kill moss and algae at the root, and a final walk-around to flag any damaged flashing or shingles before they become a leak.
Most services advertised online fall into one of two buckets:
- Moss removal + treatment — physically removes visible moss clumps, then applies a biocide/surfactant wash to kill what's left and slow regrowth.
- Full restoration wash — everything above, plus edge and gutter-line detailing and a closer inspection pass for roofs that haven't been touched in years.
Gutter cleaning is usually a separate line item, not an automatic part of a roof wash, though a lot of homeowners bundle the two since the same debris that clogs a roof valley ends up in the gutter right below it.
Does the Roofing Material Change What a Service Should Do?
The right roof washing approach depends on what's actually on the roof, since asphalt, tile, metal, and cedar shake each tolerate cleaning differently.
- Asphalt/composite shingle — soft wash only; granules are bonded on top and pressure strips them, thinning the shingle's remaining lifespan.
- Concrete or clay tile — soft wash is still preferred, since high pressure can crack or chip individual tiles, which then need replacing on their own.
- Metal roofing — more pressure-tolerant than shingle or tile, but still benefits from a lower-pressure chemical wash to avoid scratching the finish.
- Cedar shake — soft wash only, and gently; shake is porous enough that aggressive pressure can drive water under the boards.
A service that quotes the same method for every roof type regardless of material is worth a second question.
Soft Wash vs. Pressure Wash: Which Do Reputable Services Use?
Reputable roof washing services use soft washing — water at roughly 100 psi or less, combined with a cleaning solution — rather than high-pressure washing, which can drive water under shingles and strip the protective granules off asphalt roofing.
- Method — soft wash relies on chemistry and dwell time; pressure wash relies on raw force.
- Risk to shingles — soft wash is low-risk on asphalt and most tile; pressure wash can crack tile and strip granules.
- How long it lasts — soft wash typically keeps moss and algae down for 1-2 years; pressure washing alone often regrows faster since it doesn't kill the roots.
- Who should skip pressure washing entirely — anyone with asphalt shingles older than about 10 years, where the granule layer is already thinning.
If a company's quote doesn't mention soft washing by name, ask before you book.
How Much Do Roof Washing Services Cost?
Nationally, roof cleaning runs about $296–$625 for a typical job, averaging around $461, according to Angi's 2026 roof cleaning cost guide — though full pricing spans $150–$1,000 depending on roof size and condition. We price by treatment level rather than square footage:
- Moss Removal + Powder — $450 per treatment, for roofs with visible moss but no deep staining.
- Full Roof Restoration — $649 per treatment, for roofs that haven't been washed in several years or carry heavier buildup.
What Happens During a Professional Roof Wash?
A typical visit runs 1-3 hours depending on roof size and starts with a walk of the property to check pitch, material, and any already-loose shingles, since that changes how we approach the job.
- Debris clear — blow off needles, leaves, and branches so the wash solution reaches the actual roof surface.
- Pre-wet surrounding plants — landscaping gets rinsed first so the cleaning solution doesn't sit on it.
- Soft-wash application — the cleaning solution goes on at low pressure and gets time to dwell on moss and algae roots.
- Rinse — a final low-pressure rinse clears the dead growth and residue.
- Walk-around inspection — we flag any lifted shingles, damaged flashing, or clogged valleys we spot along the way.
How Often Do You Need Roof Washing Services?
Most Snohomish County roofs need a wash every 1-2 years, though shaded, tree-covered roofs or ones facing away from direct sun often need it closer to annually. The giveaway is green or black streaking, visible moss clumps along the ridge, or moss creeping under the shingle tabs.
Is DIY Roof Washing a Safe Alternative to Hiring a Service?
DIY roof washing is possible but carries real risk: most homeowner pressure washers run 2,000+ psi, well above the roughly 100 psi ceiling soft washing uses, and a slip on a wet, mossy, sloped roof is one of the more common ladder-related injuries reported each year.
A ladder, a consumer pressure washer, and a sloped roof covered in algae is less a weekend project and more a physics demonstration you didn't sign up for.
- Equipment — pro crews use soft-wash-specific pumps and chemical-safe sprayers; most rental pressure washers aren't built for roof-safe PSI control.
- Chemical handling — commercial-grade biocides need correct dilution and plant protection; DIY versions skew either too weak to work or strong enough to hurt your landscaping.
- Fall risk — a sloped, wet, algae-covered roof is exactly the surface ladders and footing perform worst on.
If you're set on doing it yourself, skip the pressure washer entirely, use a dedicated roof-safe cleaner at hose pressure, and never work a wet roof alone.
How Do You Choose the Right Roof Washing Service?
Ask whether they use soft washing by name, whether they're licensed and insured (in Washington, check the contractor registration through L&I directly rather than taking a truck decal's word for it — a roof fall isn't a small claim), and whether the quote is itemized by treatment level instead of a vague flat number. If you're in Everett or Lynnwood and want a crew that explains the quote in plain language before any work starts, that's how we price every job — see the full list of neighborhoods we cover on our service area page.
Why Snohomish County Roofs Need This More Than Most
Snohomish County doesn't really have a "dry season" so much as a "slightly less wet season," which is exactly the kind of climate moss was built to enjoy.
The county's year-round moisture and heavy tree cover — Douglas fir, western red cedar, bigleaf maple — are close to ideal growing conditions for the moss and algae that stain and shorten the life of asphalt shingles, which is why buildup here tends to come back faster than it does in drier parts of the country. Needles and leaf litter from those same trees also pack into roof valleys between washes, which is part of why the debris-clearing step at the start of the job matters as much as the wash itself. If your roof is already showing streaking or moss, a free estimate gets you a real number, not a guess, before anything gets scheduled.