Flat & Low-Slope Roofing in Toronto
Flat roofs that actually drain
Modern Toronto architecture loves a flat roof. Toronto weather does not. Ponding water, ice lensing at drains and UV-baked membranes are the usual failures; every one of them is a design problem, and every one of them we design out.
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Overview
Systems for houses, not warehouses
Most flat-roof contractors in the GTA are commercial roofers squeezing houses in between warehouse jobs. We treat a flat roof on a Forest Hill modern or a Leaside addition as part of the architecture: drainage designed with tapered insulation, terminations in metal rather than a bead of mastic, and a finish chosen because somebody looks at it from the bedroom window.
Our primary system is two-ply SBS modified bitumen (Soprema or IKO), torch-applied or self-adhered, with a granulated or reflective cap sheet. For roof terraces we install inverted assemblies with pedestal pavers; for large planes we offer 60-mil TPO and fully adhered EPDM.
Toronto fit
Where flat roofs fail in Toronto, and how we prevent it
Ponding & ice lensing
Tapered polyiso insulation gives a true 2% slope to every drain. Water leaves within 48 hours, so it can never freeze in place and lever the membrane.
Drain freeze-up
Insulated drain bowls, heated drain leads where needed, and secondary scuppers as overflow so a January freeze never floods the roof.
UV & heat
Reflective or granulated cap sheets rated for 70 °C surface temperatures; membranes carry a manufacturer system warranty, not a material-only one.
Scope
What a Ross the Roofer flat roof includes
- Removal to the deck; replacement of any damaged sheathing
- Vapour retarder and tapered polyiso insulation to R-31 or better (Ontario Building Code SB-12)
- Two-ply SBS modified bitumen, 60-mil TPO or 90-mil fully adhered EPDM
- Prefinished metal or copper parapet caps, drip edges and counter-flashings
- Insulated drains, overflow scuppers and leaf guards
- Optional pedestal-paver terrace, green roof tray system or architectural ballast
- Moisture checks and core samples of the existing roof before scoping, so nothing is hidden
Repair or replace
Flat roof repair or flat roof replacement?
Many flat roof leaks come from one weak point: a split seam, a failed drain connection, a cracked parapet flashing or a blister that has opened up. If the rest of the membrane is sound, we repair that point properly and the roof carries on. If the insulation underneath is wet, the membrane is brittle across the whole roof or water ponds for days after rain, replacement is the better investment, because a repair will not survive the next freeze.
Before we recommend either, we take moisture readings and, where needed, small core samples so you can see exactly what is under the surface.
Common flat roof repairs in Toronto
- Seam and blister repairs on modified bitumen roofs
- Drain and scupper rebuilds where water backs up in winter
- Parapet, coping and counter-flashing renewal
- Repairs around rooftop HVAC curbs, skylights and vents
- Re-sloping low spots that pond and freeze
What a flat roof costs
New flat roofs in Toronto typically run about $5 to $17 per square foot, with modified bitumen at the low end and premium assemblies and terraces at the top. Size, access, insulation and the number of drains and penetrations all affect the price. See our roof replacement cost guide for every material, or ask for a written quote.
Questions
Flat roofing, answered
Can I use my flat roof as a terrace?
Yes, with the right assembly. An inverted roof with pedestal pavers protects the membrane from foot traffic and UV. We coordinate with your architect on guards, drainage and structural loading.
Should I choose modified bitumen, TPO or EPDM?
For most Toronto homes, two-ply modified bitumen offers the best combination of puncture resistance, redundancy and repairability in freeze-thaw. TPO suits large uninterrupted planes; EPDM is excellent where the roof will be covered by pavers or a green roof.
My flat roof holds water after rain. Is that normal?
No. Ponding that lasts more than 48 hours accelerates membrane ageing and is the leading cause of winter failure. It can usually be corrected with tapered insulation or additional drainage during a re-roof.
Reviews
What Toronto Homeowners Are Saying
Real reviews from our customers on Google.
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Let's talk about your roof
A consultation comes at no cost and without obligation. We'll walk the property, look properly at the roof and tell you honestly what it needs.