Roof Moss Removal & Cleaning in Seattle
Moss is the single most common way Seattle roofs die early. It thrives in our eight-month wet season, especially on north-facing slopes and under the big conifers that shade half the city's roofs. Left alone, moss works under shingle edges, lifts them, holds water against the roof surface, and turns a 25-year roof into a 15-year roof.
The right way to remove it is unglamorous: gentle hand and brush removal, followed by a treatment that kills the remaining growth and slows regrowth. The wrong way is a pressure washer, which strips the protective granules off asphalt shingles and does more damage in an afternoon than moss does in five years. We never pressure wash composition roofs.
Moss removal is also the cheapest roof inspection you'll ever get: while the roof is being cleaned, every flashing line, boot, and valley gets eyes on it, and you hear about small problems while they're still small.
Signs this is your problem
- Green fuzz or thick moss mats visible from the street, especially on the north slope
- Shingle edges visibly lifted or shadowed by growth underneath
- Moss chunks or black debris washing into gutters
- Trees overhanging the roof dropping needles that hold moisture
- It's been more than 2-3 years since the last cleaning and treatment
How the repair works
- Dry hand removalBrushes and hand tools lift the moss mats without tearing granules off the shingles.
- Ridge-down debris clearNeedles and leaf litter out of valleys and off the field of the roof, where they trap the moisture moss needs.
- Treatment applicationA moss treatment applied to kill remaining growth at the root; regrowth slows dramatically.
- Gutter clear and reportGutters cleared of what came off the roof, plus photos and notes on anything else spotted up there.
What it costs
Typical Seattle roof moss removal with treatment runs $450 to $1,400 depending on roof size, pitch, and how established the moss is. Heavily matted roofs that haven't been touched in a decade cost more; maintenance visits cost less.
The Seattle factor
Wedgwood, Ravenna, View Ridge, and anywhere else under mature Douglas firs and cedars are moss country. North Seattle roofs shaded by trees can need attention every couple of years, while an exposed Alki roof with full sun may go five or more.