Flat roof repair in Sarnia

Flat roof services in Sarnia

Much of Sarnia's housing is older, and older houses often have flat roofs over rear additions, porches and garages. Typical signs are a stain on the kitchen ceiling, water at a skylight or a roof with several worn layers. 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.

Chemical Valley, the harbour and the North End in Sarnia

Sarnia grew with oil, the railways of the late 1850s and lumber, and it became a city in 1914. During the Second World War the Polymer Corporation brought synthetic rubber to the city, and Chemical Valley south of downtown now holds refineries and chemical plants. The grain elevator at the harbour dates to 1927. Census data shows about 71% of homes were built before 1981.

With most homes older than 1981, neighbourhoods such as the North End and the streets south of Highway 402 often have bungalows and houses with flat-roofed additions. Lambton Mall and the retail strips carry wide low-slope roofs, as do industrial service buildings, warehouses and maintenance shops tied to the plants. About 36% of homes pre-date 1961, and buildings of that age often have layers of old roofing under the top surface, which affects how repairs are planned.

Sarnia 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 Sarnia has to handle.

• 1.1 kPaGround snow load (about 23 lb per sq ft)
• 0.4 kPaRain load added to snow (Sr)
• 25 mmRain in a 15-minute storm (design value)
• 100 mmRain in one day, 1-in-50-year storm
• -16 °CJanuary design temperature
• 3,750Heating degree-days per year
• 0.47 kPaHourly wind pressure, 1-in-50-year

That snow load is about 1.2 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.

A design storm can drop 25 mm of rain in 15 minutes. On a flat roof that water has to reach a drain or scupper quickly, so clear drains and sound drain flashings matter as much as the membrane.

Environment and Climate Change Canada climate normals (1991–2020) record about 112 cm of snowfall a year at the Sarnia Airport station.

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

Homes and buildings in Sarnia

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

• 71%Homes built before 1981
• 11%Homes built since 2001
• 71%Detached and semi-detached houses
• 5%Row houses and townhouses
• 12%Apartments in buildings of 5+ storeys
• 32%Households that rent

About 71% of homes in Sarnia were built before 1981, more than in 36 of the 40 Ontario cities on this site. Older houses often have flat roofs over rear additions, kitchens and porches, sometimes with two or three layers of old roofing on top of each other. Replacing one usually starts with a full tear-off and a look at the wood deck underneath.

Source: Statistics Canada, 2021 Census Profile

Sarnia: facts for property owners

• Population of Sarnia: 72,047 (2021 Census). Source
• Sarnia is part of the Lambton County.
• City: replacing stucco, siding or shingles with the same material usually needs no permit. Source

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

Starting prices in Sarnia

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.