Roofs and moss in rainy BC

Coastal roofs fail from water that stays, not from a single storm. Needles and moss dams at valleys, overflowing gutters, and cracked flashing around chimneys and skylights are the usual path indoors. Wind-driven rain finds gaps that a calm summer inspection misses.

Moss without the damage cycle

Soft brushing on a dry day, plus keeping trees off the roof, does more than a once-a-decade blast. Aggressive pressure washing strips granules from asphalt and shortens the roof. Zinc or copper strips near the ridge can slow regrowth on some slopes; they are a supplement, not a substitute for cleaning valleys.

Cedar roofs are a different product: they need breathing room and the right treatment, not the same chemical mix you use on asphalt. If you cannot tell the material from the ground, get a photo to a roofer before buying a treatment jug.

A useful annual look

• Valleys and north slope: moss, debris, or shingles that look bald
• Flashing at walls, chimneys, skylights, and plumbing stacks
• Gutters that sag or dump behind the fascia
• Attic after a rain: damp sheathing, rusty nails, bath-fan dumping into the attic

When replacement is the honest answer

Curling, widespread granule loss in the gutters, and repeated leaks in different places usually mean the system is tired. In BC, underlayment and rainscreen details on walls matter as much as the shingle brand. A cheap reroof that ignores ventilation and flashing returns as a leak two winters later.