Flat roof repair in Ottawa

Flat roof services in Ottawa

Townhouses and row houses are common in Ottawa, and their flat roof sections often span several units. A leak can start on one unit's section and show up in the home next door. Ottawa has one of the ten heaviest design snow loads of the 40 cities on this site, so drains and parapet flashings get extra attention. We find where the water gets in, fix that spot and tell you how much life the rest of the roof has.

When a roof is past repair, we replace it with EPDM, TPO, PVC or modified bitumen, and fix the drainage so water does not sit on the new membrane. Owners and property managers also book inspections and maintenance visits.

Government core, older neighbourhoods and suburbs in Ottawa

Ottawa grew from a lumber town into the national capital in 1857, and the federal public service grew sharply during the Second World War. Centretown, Lower Town, Hintonburg and Vanier hold older housing, many Centretown homes being red brick. Suburbs such as Nepean, Gloucester, Kanata and Orleans were later joined to it, and in 2001 the region was merged into one city. Census data shows about 44% of homes were built before 1981, and about 21% are row houses.

Older brick homes in Centretown and Hintonburg often have flat roofs over rear additions and kitchens. Government and office buildings, apartment towers and hospital campuses have large low-slope roofs with parapets and rooftop equipment. The city's large tech sector adds office and industrial roofs. The newer row-house and townhouse blocks in Barrhaven and Orleans commonly use membrane roofs over flat sections.

Ottawa weather and your flat roof

Ontario's Building Code sets the climate values used to design roofs in each municipality. They show what a flat roof in Ottawa has to handle.

• 2.4 kPaGround snow load (about 50 lb per sq ft)
• 0.4 kPaRain load added to snow (Sr)
• 23 mmRain in a 15-minute storm (design value)
• 86 mmRain in one day, 1-in-50-year storm
• -25 °CJanuary design temperature
• 4,440Heating degree-days per year
• 0.41 kPaHourly wind pressure, 1-in-50-year

That snow load is about 2.7 times the Toronto figure. Snow drifts against parapets, walls and rooftop units, and the weight sits on the roof for weeks. Drains that freeze shut leave meltwater nowhere to go.

Short summer storms can still drop 23 mm of rain in 15 minutes, so drains and scuppers have to be clear and sealed.

Environment and Climate Change Canada climate normals (1991–2020) record about 232 cm of snowfall a year at the Ottawa Macdonald-Cartier Int'l A station.

Source: Ontario Building Code, Supplementary Standard SB-1, Table 1.2

Homes and buildings in Ottawa

The age and type of buildings shape the flat roofs we see. These are the 2021 Census figures for Ottawa.

• 44%Homes built before 1981
• 29%Homes built since 2001
• 47%Detached and semi-detached houses
• 21%Row houses and townhouses
• 19%Apartments in buildings of 5+ storeys
• 36%Households that rent

21% of homes in Ottawa are row houses or townhouses. Flat sections often run across several units, so a leak can start on a neighbour's part of the roof or at the joint between two units. See townhouses and row houses.

19% of homes in Ottawa are apartments in buildings of five or more storeys. Those roofs are looked after by condo boards and property managers, who need a written scope, photos and a plan that fits the reserve fund. See condo buildings and apartment buildings.

Source: Statistics Canada, 2021 Census Profile

Storms that hit Ottawa

• 21 September 2018: Tornadoes struck the Ottawa area, including an EF3 at Dunrobin and an EF2 in Nepean, damaging buildings and knocking out power to over 300,000 customers. Source
• 21 May 2022: A derecho brought a damaging downburst with winds up to 190 km/h to southern Ottawa, with many homes damaged by wind and falling trees. Source

Storms like these are when blocked drains, loose flashings and open seams show up. After a big storm, check the ceilings under the roof and send us photos of any new stain.

Ottawa: facts for property owners

• Population of Ottawa: 1,017,449 (2021 Census). Source

Rules and programs change. Confirm current details with the municipality before you start work.

Starting prices in Ottawa

Starting prices in CAD before 13% HST, based on typical Ontario contractor rates (mostly Toronto and the GTA). The final price depends on roof size, access, the layers to remove, the membrane, drains and flashings, and is confirmed in your written quote.

See all prices.