Duncan Roofing FAQ

Most asphalt re-roofs on a typical Cowichan Valley home run one to three working days — a day for tear-off and deck repair, then the underlayment, flashing and shingle courses. Steeper or more cut-up roofs take longer because staging slows every stage, and metal systems generally run longer again. We schedule your roof work into dry weather windows so your home is never left exposed to rain.

Late spring through early autumn, for a straightforward reason. Duncan averages about 30 mm of rain in July against 221 mm in November, so the dry window is wide in summer and effectively gone by late autumn. Asphalt shingles also need warmth and sun to seal down properly after installation. Roofs do get replaced through the wet months when a failure forces it, in shorter weather-dependent stages — but planned work belongs in the dry season.

Physically yes, and it is usually a false economy. Laying over an existing layer hides the sheathing entirely, so rot, delamination and previous leak damage stay undiscovered. It traps heat against the new shingles and shortens their life, and it turns the next re-roof into a two-layer tear-off at higher cost. We perform full tear-offs to the deck on every job so we can inspect your sheathing before installing new underlayment.

What matters is how much service life is left in the shingles around the failure, not the size of the failure itself. Asphalt is rated 15 to 30 years, and on this coast the lower half of that range is normal. A twelve-year-old roof with a failed chimney flashing gets a repair for $500 to $3,000. Find the same failure on a twenty-six-year-old roof with granule loss and curling edges, and that money gets spent again within a couple of years. We photograph your decking and shingle wear during our inspection so you can see whether you need a repair or a replacement.

We put seven key items in writing: old layer removal, specific underlayment, new flashing, 1/300 BC Building Code venting, sheathing allowances, disposal fees, and cleanup details. Our quotes include all seven. The roof cost guide has the full ranges.

You do not need a building permit for a like-for-like re-roof in North Cowichan unless we repair structural framing or replace attic insulation. The City of Duncan publishes no roofing-specific exemption and directs homeowners to its building inspector. We treat any roof work affecting structural framing or insulation as permit work until we confirm municipal rules.

We cover the whole Cowichan Valley Regional District — Duncan, North Cowichan including Chemainus, Crofton, Maple Bay and Westholme, Lake Cowichan, and Cowichan Bay, plus the rural areas toward Sahtlam, Glenora, Cobble Hill, Mill Bay and Shawnigan Lake. We don't apply one spec across all of it: Duncan's roughly 1,350 mm of rain a year and Lake Cowichan's roughly 2,048 mm are different enough that we assess each property on its own.

Yes, we treat moss using methods specified by shingle manufacturers, and we never use a pressure washer. We spray a 50:50 mix of laundry-strength liquid chlorine bleach and water, wait 15 to 20 minutes, and rinse at low pressure, using a leaf blower to clear moss. We never use a pressure washer on asphalt shingles because high water pressure strips away protective granules.