Flat Roofing in Thunder Bay
Flat and low-slope roofing for Thunder Bay homes and commercial buildings, built for heavy snow load, meltwater drainage, and freeze-thaw with TPO, EPDM, and modified bitumen.
Flat Roofing Built to Drain in a Northern Winter
Flat and low-slope roofs face a particular challenge in Thunder Bay: they do not shed snow. Where a pitched roof lets the snowpack slide, a flat roof carries the full snow load and all the meltwater that comes with a thaw. That makes three things decisive on a Northern flat roof: a sound membrane, proper slope so water moves to the drains, and drainage that can actually handle snowmelt. Get those right and a flat roof holds up here. Get them wrong and you get ponding, ice, and leaks.
Sleeping Giant Roofing installs and repairs flat roofs for homes and commercial buildings across Thunder Bay, with a lot of the commercial work on the Fort William side. Call (807) 501-9192 for an assessment.
Where Flat Roofs Show Up Here
Some local homes have flat or low-slope sections, additions, or modern designs with flat roofs. The bigger concentration is commercial: the Fort William side and the south-side corridors carry a large inventory of retail, office, warehouse, and shop buildings with flat roofs, all of which have to deal with serious snow load and meltwater each winter. We scale our approach to the building, from a small residential flat section to a large commercial roof.
The Systems We Install
TPO Membrane
A single-ply thermoplastic membrane with heat-welded seams, durable and often white to reflect summer heat. TPO is a strong choice for new commercial installs and replacements, with welded seams that resist the water and ice a flat roof has to handle.
EPDM Rubber Membrane
A proven synthetic rubber membrane that has protected flat roofs for decades. EPDM is durable and a reliable choice for both residential and commercial flat roofs.
Modified Bitumen
A multi-ply asphalt-based system suited to certain retrofits and applications, including roofs being re-covered over existing built-up systems.
Drainage Is Everything
The most common flat-roof problem we are called for is ponding water, and it almost always traces back to drainage. A flat roof needs enough slope to move water to the drains, and drains and overflows sized to handle both rain and snowmelt. Standing water is hard on any membrane, and in our climate it freezes and thaws over and over, working the membrane until it fails. When we install or replace a flat roof, we correct the slope with tapered insulation and make sure the drainage can do its job. When we repair one, we look at why it ponded, not just where it leaked.
Repair or Replace
If your flat roof has isolated membrane damage or a localized leak, a repair may be all it needs. If it has chronic ponding, widespread membrane failure, or it is near end of life, a full replacement with corrected drainage is the better investment. A roof inspection gives you a clear picture, and our broader roof replacement process applies to flat roofs as well.
Get a Free Flat Roofing Estimate
We will assess your flat roof, identify any drainage issues, and recommend the right system. Call (807) 501-9192 or request a free estimate online. We serve homes and businesses across Thunder Bay and Northwestern Ontario.
How It Works
Free Consultation & Inspection
Give us a call or fill out our online form. We will come to your property, inspect your roof thoroughly, and discuss your options, all at no cost and no obligation.
Detailed Written Estimate
You will receive a clear, itemized quote that covers materials, labour, timeline, and warranty details. No hidden fees, no surprises, just honest pricing.
Expert Installation
Our experienced crew handles your project from start to finish with quality materials and clean, professional workmanship. We keep you updated every step of the way.
Final Walkthrough & Warranty
Once the job is done, we walk through everything with you to make sure you are completely satisfied. You get a written warranty so your investment is protected for years to come.
Frequently Asked Questions
Do flat roofs hold up under Thunder Bay snow load?
They can, when built correctly. A flat roof does not shed snow the way a pitched roof does, so the snow load and the meltwater both sit on it. That makes the membrane, the slope to drain, and the drainage outlets critical. We build flat roofs with proper tapered slope and adequate drains and overflows so water moves off rather than ponding and refreezing. A well-built flat roof handles our winter; a poorly drained one does not.
What flat roofing systems do you install?
TPO and EPDM single-ply membranes for most new and replacement work, and modified bitumen for certain retrofits and applications. TPO is a durable welded-seam membrane, often white to reflect summer sun, while EPDM is a proven rubber membrane. We recommend the system that fits your building, budget, and how the roof drains and is used.
Why does my flat roof keep ponding water?
Ponding usually means the roof lacks adequate slope to the drains, or the drains are undersized or blocked. Standing water is hard on any membrane and, in our climate, it freezes and thaws repeatedly, accelerating wear and leaks. The fix is correcting the slope with tapered insulation and making sure the drainage can actually move the water and snowmelt. We address the cause rather than just patching the wet spots.
Do you do both residential and commercial flat roofs?
Yes. Some Thunder Bay homes have flat or low-slope sections, and the Fort William side in particular has a large base of commercial and industrial buildings with flat roofs. We work on both, scaling the system and the detailing to the building.
How long does a flat roof last in our climate?
A quality flat membrane roof generally lasts about 20 to 30 years, with our cold, snowy climate tending toward the lower end of that range, especially if drainage is poor. Good installation, proper slope, and keeping the drains clear all extend the life. Regular inspection helps catch small membrane issues before they become leaks.