Moss: Your Roof's #1 Enemy in Washington
If you live in Washington state, moss on your roof isn't a matter of if — it's a matter of when. Our damp, mild climate creates perfect growing conditions for moss, which can cause serious damage if left unchecked. Moss roots work under shingles, lifting them and creating pathways for water that leads to rot, leaks, and premature roof failure.
What You Should Never Do: Power Wash
The single biggest mistake homeowners make with roof moss is reaching for a pressure washer. High-pressure water strips the protective granules from asphalt shingles, dramatically reducing their lifespan. It can also force water under shingles and into the roof deck. Never power wash an asphalt shingle roof — the damage far outweighs any benefit.
Zinc Strips: A Preventive Approach
Zinc strips installed along the roof ridge can help prevent moss growth. When rain washes over the zinc, it releases zinc ions that create an inhospitable environment for moss. While zinc strips won't remove existing moss, they can significantly slow new growth between professional treatments.
Professional Moss Treatment
Professional moss removal involves gentle application of moss-killing treatment solutions followed by careful hand removal of dead moss. The process typically includes:
- Application of professional-grade moss treatment
- Waiting period for moss to die (usually 2-4 weeks)
- Gentle hand removal of dead moss
- Debris cleanup from roof and gutters
- Optional zinc strip installation for prevention
How Often Is Treatment Needed?
In most parts of Northwest Washington, professional moss treatment is recommended every 1-2 years depending on your roof's sun exposure, nearby tree coverage, and roof material. North-facing roof slopes and heavily shaded roofs may need annual treatment, while sun-exposed roofs can often go 2-3 years between treatments.