Roof Replacement Cost in Ottawa: 2026 Guide

Roof Size, Pitch and Complexity

Roof area sets the material order, but pitch and shape set the labour. A walkable 4/12 to 6/12 roof goes quickly, while 9/12 and steeper needs roof jacks, harnesses on anchors and slower work. That is why steep roofs sit at the top of the per-square range.

Every valley, dormer, skylight, chimney and wall intersection needs cutting and flashing by hand. A simple gable on a Barrhaven townhouse and a hip roof with three dormers can have the same area and very different prices.

Tear-Off Layers and Decking Repairs

Labour and tear-off are the most expensive part of most replacements, and hidden deck damage is the most common reason a final bill grows. Every extra layer of old shingles adds removal time, bin weight and disposal cost.

Once the old roof is off, we replace any soft, delaminated or rotted sheathing before anything new goes down. Ask every contractor to quote a written price per 4x8 sheet of replacement decking, so the cost is known before the job starts.

Many 1950s and 1960s Ottawa homes still have plank (board) sheathing with gaps between boards. Shingle manufacturers generally want a solid deck, so those roofs may need a plywood or OSB overlay, which is a legitimate extra worth seeing in writing.

Ventilation, Flashing and Ice-and-Water Shield

These items add a modest share of the total but decide how long the roof lasts. Ontario's Building Code requires self-adhered eave protection on shingle roofs in our climate, running at least 900 mm up the slope and at least 300 mm inside the inner face of the exterior wall.

Good quotes also include new step and counter flashing at walls and chimneys, a new drip edge, membrane in the valleys, and balanced intake and exhaust ventilation. Reusing rusty old flashing saves a few hundred dollars and causes many of the leaks we repair on roofs under ten years old.

Products to look for by name include Grace Ice & Water Shield, IKO StormShield or GAF WeatherWatch at the eaves and a synthetic underlayment over the rest of the deck.

Access, Permits and Disposal

Access costs more on tight urban lots in the Glebe, Hintonburg or Sandy Hill, where the bin may not fit on the driveway and materials are carried by hand. Large trees, glass sunrooms and gardens against the house add protection time.

The City of Ottawa lists installing asphalt shingles as work that does not need a building permit, but structural repairs do, and homes in heritage districts are treated differently. Our Ottawa roofing permits guide explains when a permit or heritage approval adds cost and time.

Disposal is priced by bin size and weight, which is why a two-layer tear-off costs more to haul away. Quotes should state whether the bin, its permit or placement, and magnetic nail sweeps are included.