Roofing services · Duncan
Roof Replacement in Duncan
We handle complete asphalt re-roofs with full tear-off, deck repair, new underlayment and corrected venting, giving you a written scope before we take off a single shingle.
Cowichan Roofing provides full roof replacements across Duncan, North Cowichan and the Cowichan Valley. We strip old shingles down to the sheathing, inspect and repair damaged deck boards, lay new underlayment, and bring your ventilation to the BC Building Code minimum of 1/300 of your insulated ceiling area. Cowichan Roofing installs asphalt re-roofs across the Cowichan Valley Regional District, Duncan and Vancouver Island. We complete most typical residential re-roofs for $8,000 to $20,000, or roughly $4 to $9 per square foot installed. Cowichan Roofing installs asphalt systems that carry a 15 to 30 year service life across the Cowichan Valley and Vancouver Island in British Columbia. We remind homeowners that the lower half of that range is normal locally, where roofs stay wet from November through January.
Most Cowichan Valley roofs come off because the system underneath has failed — brittle underlayment, sheathing softened under a chronic valley leak, or an attic that never had enough intake venting — well before the shingles themselves look tired. A full replacement gives us the chance to fix your underlayment, sheathing and venting all at once. We tear back to the deck, paying as much attention to our initial assessment as to your shingle choice.
What a full tear-off includes
Every existing layer comes off down to the sheathing. That is the only way to see the deck, and on Cowichan Valley homes there is usually something to find — a soft patch below a valley, a rusted-out flashing at a chimney, or plywood delaminating along a north-facing slope that never dries out. We replace damaged sheathing before we put down any new underlayment or shingles.
We rebuild your roof step by step: ice-and-water membrane at eaves, valleys and penetrations, synthetic underlayment across the field, new metal flashing and drip edge, and then your new shingles. We install or correct your ridge and intake venting as part of the same replacement job. The old roof is loaded out and the site is magnet-rolled for nails before the crew leaves.
Roofing over an existing layer saves money on day one, but costs you more over the life of your roof. It hides deck condition entirely, traps heat against the new shingles, and makes the next tear-off a two-layer job, with twice as much old material to load out.
Ventilation decides how long the roof lasts
BC Building Code Section 9.19.1.2 sets the unobstructed vent area for a roof space at not less than 1/300 of the insulated ceiling area, tightening to 1/150 where the slope is under 1 in 6 or the roof is built with joists. A large share of older Cowichan Valley homes fall short of that, usually because intake venting at the soffits was blocked by insulation or never installed to begin with.
Warm moist air collects at the underside of the sheathing, condenses through the wet months, and the deck stays damp under a roof that looks fine from the street. Shingle life drops, plywood delaminates, and mould appears in the attic. Balanced intake at the eaves and exhaust at the ridge is a small line item during a re-roof and an expensive retrofit afterwards.
What moves the price
Roof size and pitch come first — steeper roofs need staging and slow the work. We look at how many shingle layers must come off, how much sheathing needs replacing, the number of penetrations and valleys, bin access, and whether we need to build new venting. Two Duncan houses with the same footprint can differ by $6,000 based on job conditions. We inspect your roof in person before giving you a price. We detail full price ranges and project factors in our roofing cost guide.
Typical price range
$8,000 – $20,000
Most asphalt re-roofs in the Cowichan Valley fall between $8,000 and $20,000 — a planning range, not a quote. We give you an exact price after inspecting your roof in person.
Roofing in nearby communities
Keep exploring
- Compare roof costsFull cost ranges for the Cowichan Valley — asphalt, metal, repairs — and what changes the figure.
- Roof RepairRoof leak and flashing repair in Duncan and the Cowichan Valley — chimneys, skylights, valleys, storm damage and lifted shingles. Most repairs $500–$3,000.
- Metal RoofingStanding-seam and metal panel roofing in Duncan and the Cowichan Valley — 40–70 year service life, no moss mat, concealed fasteners. Typically $18,000–$45,000.
- Cowichan Roofing home
Get a written roofing quote
Serving Duncan, North Cowichan, Lake Cowichan and Cowichan Bay across the Cowichan Valley Regional District.