Northern Ontario
Flat roof repair in Thunder Bay
We repair, replace and maintain flat roofs in Thunder Bay: houses, garages and additions, condo and apartment buildings, plazas, offices and warehouses. Send photos and a few details for a written quote.
Flat roof services in Thunder Bay
Much of Thunder Bay'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. Thunder Bay has one of the five 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.
Two cities in one: Fort William and Port Arthur
Thunder Bay was formed on 1 January 1970 by merging Fort William and Port Arthur with two townships. Rail and grain drove the early twentieth-century boom, with grain elevators, pulp and paper mills and the Neebing rail yards. Neighbourhoods include Westfort, Current River and Northwood. Census data shows about 73% of homes were built before 1981, and about 39% before 1961.
The older housing in Westfort and Current River includes small brick and frame homes with flat-roofed additions. Each former downtown has its own commercial blocks with parapets. The grain and rail lands and the Kaministiquia River corridor have large industrial roofs, such as the railcar plant built in 1912, now run by Alstom. Newer growth is limited, with only about 9% of homes built since 2001, so most roofs are aging.
Thunder Bay 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 Thunder Bay has to handle.
- 2.9 kPaGround snow load (about 61 lb per sq ft)
- 0.4 kPaRain load added to snow (Sr)
- 23 mmRain in a 15-minute storm (design value)
- 108 mmRain in one day, 1-in-50-year storm
- -31 °CJanuary design temperature
- 5,650Heating degree-days per year
- 0.39 kPaHourly wind pressure, 1-in-50-year
That snow load is about 3.2 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.
Short summer storms can still drop 23 mm of rain in 15 minutes, so drains and scuppers have to be clear and sealed.
Source: Ontario Building Code, Supplementary Standard SB-1, Table 1.2
Homes and buildings in Thunder Bay
The age and type of buildings shape the flat roofs we see. These are the 2021 Census figures for Thunder Bay.
- 73%Homes built before 1981
- 9%Homes built since 2001
- 70%Detached and semi-detached houses
- 3%Row houses and townhouses
- 5%Apartments in buildings of 5+ storeys
- 32%Households that rent
About 73% of homes in Thunder Bay were built before 1981, more than in 38 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.
Thunder Bay: facts for property owners
- Population of Thunder Bay: 108,843 (2021 Census). Source
- City permit page lists 'flat roofing system replacement' among building-systems applications that need a permit. Source
Rules and programs change. Confirm current details with the municipality before you start work.
Starting prices in Thunder Bay
| Item | Starting price |
|---|---|
| Small leak repair (patch, seam or puncture) | from $350 per repair |
| Small flat roof replacement (garage, porch or addition) | from $4,000 per roof |
| House flat roof replacement (about 1,000 sq ft) | from $8,000 per roof |
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.
Roofs we work on in Thunder Bay
Nearby cities
Flat roofs in Thunder Bay: questions
How much does flat roof repair cost in Thunder Bay?
A small leak repair starts from $350 per repair and a new house flat roof starts from $8,000 per roof. Prices in Thunder Bay depend on access, layers to remove and the membrane. See pricing.
Should I clear snow off a flat roof in Thunder Bay?
Only if the snow is deep and wet, drifts are building against walls or units, or the building shows signs of stress. Use a plastic shovel, leave a layer on the membrane and never use picks or salt. If in doubt, ask a professional.
Do I need a permit to replace a flat roof in Thunder Bay?
City permit page lists 'flat roofing system replacement' among building-systems applications that need a permit. Rules can change, so confirm with the building department before you start. See re-roofing permits in Ontario.
My Thunder Bay house is older. Can the flat roof go on over the old one?
Sometimes one new layer can go over one old layer, but on older houses we often find two or three layers already, wet insulation or soft deck boards. Then a full tear-off is the safer choice. See repair or replace.
Do you also work near Thunder Bay?
Yes, including Sault Ste. Marie, Sudbury, North Bay and the rest of northern Ontario. See Northern Ontario.
Leak, damage or an old flat roof?
Send a few details and photos. We reply by email with next steps and a written quote.