Flat Roof Replacement and Repair
GAF CERTIFIED ROOFING CONTRACTOR • 15+ YEARS GTA EXPERIENCE
YS Roofing installs and repairs flat roofing systems, including EPDM rubber, TPO, and modified bitumen, on residential additions, garages, and low-slope sections, as well as commercial buildings across Toronto and the GTA. Every job starts with a free, on-site estimate and a written proposal before work begins.
Signs You Need a New Roof
■ Standing Water that Remains
Blistering, cracking, or bubbling in the membrane surface, especially around seams and roof edges
■ Membrane Separation from Flashing
A membrane that has pulled away from flashing at a wall, parapet, or rooftop unit
■ Blistering, Cracking/Bubbling
Soft or spongy spots on the roof deck, or water staining on the underside of the deck visible from inside the attic
■ Interior ceiling stains directly
Interior ceiling stains directly below a flat roof section, which often appear faster than on a sloped roof because there is less space for water to travel before it becomes visible
■ A flat roof section installed
A flat roof section installed at the same time as the rest of the building and now approaching or past its expected service life
What Is Included
- Installation or replacement using EPDM rubber, TPO, or modified bitumen, matched to the building type, slope, and application. Our material guide compares the three in detail; in short, EPDM is a durable single-ply option, TPO offers a reflective surface with heat-welded seams, and modified bitumen suits roofs that need extra puncture resistance.
- Insulation correction during replacement, including added polyiso board above the deck where the existing insulation has settled or was never sufficient
- Drainage assessment and correction, including scuppers, drains, and slope, to stop standing water rather than patch around it
- Flashing and parapet detailing at walls, curbs, and rooftop units, which is where most flat roof leaks actually start
- Site protection and full cleanup before the crew leaves
How the Job Runs
- Consultation. We inspect the existing flat roof, check drainage and insulation depth, and discuss membrane options for the building.
- Detailed Proposal. A written scope covering membrane type, insulation, drainage corrections, and price, with the plan fixed before work starts.
- Professional Installation. The crew removes the old membrane, corrects any insulation and drainage issues found, and installs the new system to manufacturer specification.
- Final Inspection. A walk-through confirming seams, flashing, and drainage before the crew leaves.
What Most Homeowners Get Wrong
The most common mistake is treating a flat roof leak as a simple patch job when the real problem is drainage rather than the membrane. A membrane can be in reasonable condition and still leak if water is pooling against a wall or parapet instead of draining, and patching the membrane without correcting the slope or the drain just moves the leak somewhere else. A second mistake, common on older GTA homes, is assuming insulation can be added later if it was skipped originally or has settled over time. Attic insulation in older homes often started around 10 inches deep and compresses to roughly 6 inches after years of settling, and a flat roof does not have a cavity where insulation can be added once the membrane is in place. Replacement is the point where 2 to 4 inches of polyiso insulation board can be added above the deck, and that option is gone once the new membrane goes down. A third mistake on commercial buildings is deferring a small repair until it affects operations, when a replacement scheduled around the membrane’s service life avoids an unplanned closure.
GTA Conditions That Matter
Flat roofs in the GTA deal with more snow load and more freeze-thaw cycling at the membrane surface than a sloped roof, since standing snow does not shed the way it does off a pitched roof. Ponding water that would simply run off a sloped roof can sit on a flat roof through a freeze-thaw cycle, which stresses the membrane at the pond’s edge over repeated winters. Rooftop units, vents, and parapet walls are also more common on flat roofs, and each one is a flashing detail that has to be maintained, since flashing failures account for a large share of flat roof leaks regardless of which membrane is installed.
Service Areas
YS Roofing provides flat roof replacement and repair across
Why YS Roofing
YS Roofing is based in Markham and has completed more than 1,000 residential roofing projects across Toronto and the GTA, and also installs and repairs flat roofing systems for commercial properties in the same region. Every estimate is free, and financing is available for larger jobs. A written proposal before work starts and a final inspection before the crew leaves apply to flat roof work the same way they apply to a full roof replacement.
FAQ
How much does flat roof replacement cost?
Cost depends on the roof size, the membrane chosen, and whether drainage or insulation corrections are needed. We do not publish a per-square price online because those variables change the total meaningfully from building to building. A free, on-site estimate gives an exact, written figure.
What is the best material for a flat roof: EPDM, TPO, or modified bitumen?
It depends on the building and the priorities. EPDM is a durable, cost-effective single-ply option. TPO offers a reflective surface and heat-welded seams. Modified bitumen suits roofs that need extra puncture resistance. Our EPDM versus TPO versus modified bitumen guide covers the comparison in more depth.
How long does a flat roof last?
Most flat roofing systems last 15 to 25 years depending on the material, installation quality, and how well drainage is maintained. Ponding water or poor drainage can shorten that regardless of which membrane is installed, which is why we assess drainage as part of every inspection.
Do you install flat roofs on commercial buildings?
Yes. YS Roofing installs and repairs flat roofing systems on commercial properties as well as residential additions, garages, and low-slope sections.
Can a flat roof be repaired instead of replaced?
Sometimes. An isolated seam failure or a single damaged flashing point on an otherwise sound membrane is often a repair. Widespread blistering, repeated ponding, or a membrane at the end of its service life is usually past the point where a repair is the economical choice. We will tell you which situation applies during the inspection.
Can flat roofing be installed in the winter?
It can, though some membrane types are sensitive to cold temperatures during installation, particularly where seams are heat-welded. We account for this when scheduling a winter job and will flag any conditions that affect timing at the estimate.
Related Guides
What Happens Next
Book a free, on-site estimate and we will inspect your flat roof, assess drainage and insulation, and provide a written proposal before any work starts. Call 647-667-1367, or contact us to get a quote.