Roof Maintenance in Duncan

Moss does not simply sit on a roof. It holds water against the shingle mat, lifts the lower edge of the course above it, and works granules loose as it spreads. Left through a few Cowichan winters it turns a mid-life roof into a replacement.

The Asphalt Roofing Manufacturers Association is explicit about the method: a 50:50 mix of laundry-strength liquid chlorine bleach and water, applied with a sprayer, left 15 to 20 minutes, then rinsed with low-pressure water, with dead moss loosened by a leaf blower rather than scraped. ARMA is equally explicit about what not to do — a pressure washer on asphalt shingles causes granule loss and very likely premature failure of the roof system.

That rules out most of what gets sold locally as roof cleaning. It also rules out retrofitting zinc or copper strips to an existing roof, which ARMA discourages because fastening them means either exposed nails or breaking the shingle sealant bond. Those belong at replacement time, or in shingles that already carry copper granules.

Gutters and valleys come first in a valley this heavily treed. Douglas fir and cedar drop enough needles in one autumn to pack a valley solid, and November averages over 200 mm of rain in Duncan — a blocked gutter overtops and runs behind the fascia rather than away from the house. Clearing before the wet season is worth more than clearing after it.

Then the small things that end roofs quietly: cracked sealant at vent boots and skylights, a lifted shingle where a seal strip has broken, loose chimney counter-flashing, and moss re-establishing on the north slope. A documented visit with photos is enough to know whether the roof is holding its line or heading toward replacement — and whether any of the work ahead touches structure, which is the point at which the permits guide becomes relevant.