Quick answer
Roof moss sheds clumps into gutters every time it rains, which clogs downspout outlets and adds heavy wet debris. Remove moss gently by hand or soft brush (never pressure wash shingles), apply a roof moss treatment per its label, consider zinc strips near the ridge, trim branches that shade the roof, and clean the gutters after any moss removal.
Why moss loves Northwest roofs
Mild temperatures, long wet seasons and shade from tall firs keep north-facing roof planes damp most of the year. Moss takes hold in the gaps between shingles and spreads.
What moss does to your roof and gutters
- Holds water against shingles and lifts their edges
- Lets wind-driven rain get under shingles
- Washes into gutters and plugs downspouts
- Grows on top of gutter guards
Removal and prevention
- Brush moss off gently from the top down with a soft brush, never against the shingle overlap.
- Apply a moss treatment labeled for roofs and follow the label for plants and runoff.
- Install zinc strips near the ridge to slow regrowth.
- Trim branches to let more sun reach the roof.
- Clean gutters and downspouts afterward.
Frequently asked questions
Is pressure washing a roof bad?
Yes for asphalt shingles. It strips protective granules and can void warranties.
When should moss be removed?
Late summer and early fall are ideal, before the heavy rains, with dry days for treatment to work.
Need a hand?
- Roof Moss Removal: Gentle moss removal and zinc-based treatment that protects shingles and keeps gutters from refilling.
- Gutter Cleaning: Hand-cleaned gutters, flushed downspouts, roof edge cleared and everything bagged and hauled away.
- Gutter Guards: Micro-mesh and screen guards chosen for fir needles, maple leaves and moss, not a one-size pitch.