Spokane's frequent winter rains and shaded north slopes on older homes in areas like the South Hill and Logan neighborhoods create ideal conditions for moss to take hold on asphalt shingles and cedar shakes. Left untreated, moss traps moisture against the roof deck, accelerating granule loss and leading to leaks during freeze-thaw cycles. Treatment begins with a low-pressure application of zinc-based or copper sulfate solutions that kill the moss at the root without damaging shingles, followed by gentle brushing to clear debris from valleys and around chimney bases.
Homeowners in Spokane County often see moss return within two seasons if gutters remain clogged with pine needles from nearby trees. Effective treatment includes clearing those gutters and applying a follow-up preventive spray along the ridge lines. Crews working from the 1106 N Washington St base schedule most jobs in spring or fall when temperatures stay above 50 degrees to ensure the solution activates properly before the next rain event.
Edge cases include steep pitches on historic homes in Browne's Addition where fall protection and scaffolding become necessary, and metal roof sections where different biocides must be used to avoid corrosion. Always inspect flashing around skylights and vents during the same visit, as moss often signals underlying moisture issues that simple washing will not resolve.
Technician insight
In Spokane the thing that catches most people out with moss removal treatment is how quickly it returns on north-facing slopes of 1950s–1970s homes in the South Hill when gutters stay full of pine needles; skipping the gutter step means the treatment only lasts one season.
South Hill ranch roof
Heavy moss covered the shaded north side of a 1960s ranch in the South Hill. Inspection showed clogged gutters feeding constant moisture into the valleys. Treatment killed the moss, gutters were cleared, and zinc strips were added along the ridge. The roof dried out and no new growth appeared the following winter.
Moss Removal Treatment Services We Offer
✓Asphalt Shingle Moss Treatment
Kills and removes moss from common Spokane asphalt roofs while preserving granule integrity against repeated wet winters.
✓Cedar Shake Moss Removal
Gentle cleaning and treatment for cedar roofs found on older South Hill homes that avoids harsh chemicals that can strip natural oils.
✓Gutter Moss and Debris Clearing
Removes moss-laden debris from gutters and downspouts to prevent backup that leads to fascia rot in Spokane's rainy season.
✓North Slope Preventive Spray
Applies zinc strips and preventive solution along shaded roof sections most prone to regrowth after initial removal.
✓Valley and Flashing Moss Treatment
Targets moss buildup in valleys and around penetrations where water pools on Spokane homes with complex rooflines.
Moss Removal Treatment Cost in Spokane, WA
| Service | Typical Range | What Affects It |
|---|---|---|
| Single-story asphalt roof moss treatment | $250–$450 | Price rises with heavy coverage or two-story access needs. |
| Cedar shake moss removal | $350–$650 | Extra care required on older Spokane homes with wood roofs. |
| Gutter clearing with moss treatment | $150–$300 | Often bundled when roof work is already scheduled. |
| Zinc strip installation | $100–$200 | Added to slow regrowth on north slopes common in Spokane. |
Ranges are typical for Spokane, WA and confirmed with an exact written quote before any work starts.
How it works
- 1
Roof Inspection
Walk the roof to identify moss coverage, note shingle condition, and check for existing damage in Spokane's typical older housing stock.
- 2
Treatment Application
Apply EPA-approved moss killer via low-pressure sprayer and allow dwell time for root kill before any mechanical removal.
- 3
Gentle Removal
Brush and rinse dead moss from shingles, valleys, and gutters without high pressure that can dislodge granules.
- 4
Preventive Measures
Install zinc strips or apply follow-up treatment along ridges and north-facing slopes to slow regrowth.
Pricing
Most Spokane moss removal jobs fall into mid-range pricing depending on roof size, pitch, and whether preventive zinc strips are added.