Flat & Commercial Roofing in Ontario
Flat and low-slope roofing covers a different set of problems than a house with shingles. This category includes contractors who install and repair TPO, EPDM rubber, modified bitumen, built-up (tar and gravel), and metal roofing on plazas, warehouses, apartment buildings, schools, and industrial sites. The work leans heavily on drainage, seam welding, flashing details around rooftop units and parapets, and insulation choices that affect both energy bills and long-term wear. We track 60 businesses across Ontario doing this kind of work, from small crews that handle repairs and re-roofs to larger firms that bid on new-build commercial projects.
Before you hire, look past the lowest quote. Ask what membrane system the crew is actually certified to install (manufacturers like GAF, Soprema, or Firestone tie their warranties to certified installers), what the workmanship warranty covers versus the material warranty, and whether they'll give you a written scope with drainage and flashing details, not just a price per square foot. A contractor who inspects the deck and insulation before quoting is a better sign than one who quotes off a satellite photo.
Our scores weigh review volume and rating trends, how long a business has operated, and complaint patterns, so you can compare contractors on more than a sales pitch. See the ranked list of Ontario roofing contractors for our top picks in this category, and read our scoring methodology to see exactly how we calculate it.
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All flat & commercial roofing, ranked by score and relevance
109 businesses. The order weighs each business's overall score by how much of its reviewed work is flat & commercial roofing, so a lower-scored specialist can rank above a higher-scored generalist. Filter and sort below, or open the full map view.
When you submit a quote or contact form through this site, your enquiry may be shared with partner providers who can do the work. We may earn a referral fee from these partners, but our rankings and scores are determined solely by our published method and are never affected by referral fees.
Common questions about flat & commercial roofing
- How much does a commercial flat roof replacement cost in Ontario?
- Most flat roof replacements run somewhere between $6 and $14 per square foot depending on the membrane system, deck condition, insulation upgrades, and building height, though large industrial jobs and complex drainage work can push that higher. Get at least two written quotes that break out material, labour, and disposal, since ballpark phone quotes rarely hold once a crew is on the roof.
- How long does a flat or commercial roof last before it needs replacing?
- TPO and EPDM membranes typically last 20 to 25 years, modified bitumen around 15 to 20, and built-up (tar and gravel) roofs can reach 20 to 30 years with regular maintenance. Actual lifespan depends heavily on drainage, foot traffic from rooftop equipment servicing, and whether small punctures and seam failures get caught and patched early.
- What should I expect during a flat roof installation or repair?
- Expect the crew to inspect the deck and insulation first, since a soft or wet deck needs to be addressed before a new membrane goes down. A full tear-off and replacement on a mid-size commercial building often takes several days to a couple of weeks depending on weather and building size, while targeted repairs to a seam or flashing can often be done in a single visit.
- How can I tell if a flat roofing contractor does quality work?
- Look for manufacturer certification on the specific membrane system they're proposing, a written workmanship warranty separate from the material warranty, and references from other commercial or multi-unit properties they've worked on. Contractors who walk the roof and photograph drains, flashing, and problem areas before quoting are generally more careful than ones who quote sight unseen.
Guides to choosing flat & commercial roofing
- Signs your flat or commercial roof needs repair before it fails
The visible and less obvious warning signs that a flat or low-slope roof needs attention, before a small issue turns into a costly leak.