Commercial Roof Leak Repair in Toronto
Leaks traced to the true entry point, not just patched at the drip. Most repairs are finished in one day.
Call 1-833-775-7663 24/7 emergency line · Toronto and the GTA · Most single leaks $500 to $2,500 CAD
Karol Rajkowski
Vice President, OYH Roofing
Published September 30, 2026 · Updated October 1, 2026 · 8 min read
Short answer
Commercial roof leak repair in Toronto costs $500 to $2,500 CAD per leak on most jobs, as of October 2026, and most flat-roof repairs are finished in a single day. Water can travel several metres along the roof deck before it shows up inside, so tracing the leak properly is what makes the repair last.
What should you do first when a commercial roof is leaking?
Contain the water, protect the interior and document everything before repairs begin. That is the first step in any commercial roof leak repair in Toronto.
Move stock, equipment and electronics away from the leak, put containers under active drips, and photograph the damage with the date so you can document it for your insurer. Then take these steps, in order:
- Restrict access to wet floors and stained ceiling areas. Slip hazards create liability fast.
- Note where the water shows inside and what is on the roof above it, if you know. That speeds up leak tracing.
- Call a commercial flat roofing contractor, not a general handyman. TPO, EPDM and modified bitumen each need different repair methods and materials.
- Keep staff off the roof. Do not send anyone up to look, especially in rain, snow, wind or at night. Leave the roof to a crew with proper fall protection.
How much does commercial roof leak repair cost in Toronto?
Commercial roof leak repair in Toronto costs $500 to $2,500 CAD per leak on most jobs, as of October 2026. Larger repair areas are usually priced by the square foot, at roughly $4 to $12 depending on the membrane.
| Repair type | Typical cost, most jobs | Typical timeline |
|---|---|---|
| Membrane puncture or split (patch) | $500 to $1,500 | Same day |
| Flashing or penetration repair (vents, HVAC curbs, pipes) | $600 to $2,000 | Same day |
| Seam repair (TPO or PVC re-weld, EPDM re-seam) | $500 to $2,500 | 1 day |
| Roof drain repair or re-flashing | $750 to $2,500 | 1 day |
| Infrared moisture scan (leak detection survey) | Quoted per building | Half day |
Three things move the price of commercial roof leak repair in Toronto most: how far water has travelled into the insulation, roof access (a two-storey warehouse in Etobicoke is priced differently from a twelve-storey building downtown), and whether wet insulation must be cut out and replaced before the membrane is closed. After-hours emergency calls carry a call-out premium, so ask for the current rate when you call.
With commercial roof leak repair in Toronto, the cheapest leak is the one caught early. A small flashing repair that is ignored for a season can turn into a much larger insulation replacement.
What causes most commercial roof leaks?
Most commercial roof leaks start at penetrations, flashings, seams and drains, not in the open field of the membrane.
On calls for commercial roof leak repair in Toronto, Mississauga and Oakville, the same failure points come up again and again:
- Flashing failures at HVAC curbs, vents and parapet walls; see our roof flashing repair guide.
- Seam separation on aging single-ply membranes (TPO, EPDM, PVC); see our membrane roof repair guide.
- Clogged or poorly flashed drains that cause ponding water.
- Membrane punctures from trades traffic, dropped tools or wind-blown debris.
- Freeze-thaw damage. Each winter cycle above and below zero works water deeper into small openings.
For commercial roof leak repair in Toronto, the climate is the multiplier. A hairline seam gap opens up fast under freeze-thaw cycles and spring melt. That is why the National Roofing Contractors Association (NRCA) recommends roof inspections at least twice a year, and why spring and fall inspections are part of our maintenance programs.
How do roofers find the source of a leak on a flat roof?
Roofers find the source of a flat roof leak by working back from the interior evidence, because the drip is almost never directly below the breach.
On a low-slope roof, water gets through the membrane, travels along the deck or vapour barrier, sometimes for several metres, and comes out at the nearest opening, such as a light fixture or a deck seam. Professional leak tracing follows a process:
- Interior mapping. Every stain and drip point is located and marked against the roof features above.
- Surface inspection. Every seam, flashing, penetration and drain upslope of the interior evidence is examined.
- Water testing. Water is applied to suspected points to confirm the entry path.
- Infrared or moisture scanning. For chronic leaks, thermal imaging maps wet insulation without opening the roof.
Tracing is the core of commercial roof leak repair in Toronto. Guess-and-patch repairs are why some buildings fix the same leak three times. Tracing it once, correctly, costs less.
Not sure what shape your roof is in?
Book a free commercial roof assessment and get a documented condition report before the next storm.
Call 1-833-775-7663Request an assessmentShould you repair or replace a leaking commercial roof?
Repair the roof when leaks are isolated and the membrane is sound, and plan a replacement when leaks are widespread, the insulation is saturated, or yearly repair spending approaches 25 to 30 per cent of the replacement cost.
| Question | Repair fits when | Replacement fits when |
|---|---|---|
| Where are the leaks? | At specific flashings, seams or penetrations | At new locations every season |
| What does the moisture scan show? | Dry insulation outside the leak zone | Saturation across large areas |
| What shape is the membrane in? | Intact, usually under 15 to 20 years old | Seams failing generally, not at one detail |
| Where does the other option win? | Replacement resets the warranty | Repair costs far less up front |
On our own jobs, from new roofs to commercial roof leak repair in Toronto, we have seen both outcomes, and we put the moisture-scan results in front of the client before recommending either. Replacement work also has to meet the current Ontario Building Code, which older roofs often pre-date. For an example of a full replacement, see the 53,000 square foot industrial recover in Mississauga, or browse our completed projects.
How long does a commercial roof leak repair take?
Most single-leak jobs for commercial roof leak repair in Toronto take one day or less, including leak tracing, and an emergency temporary seal can stop active water entry in 2 to 4 hours.
| Scope | Typical timeline |
|---|---|
| Emergency temporary seal | 2 to 4 hours |
| Single leak, traced and permanently repaired | One day or less |
| Several drains, long seam runs or insulation replacement | 2 to 3 days |
| Winter repair | Temporary seal during snow or ice, permanent repair once the surface is dry |
Winter repairs are possible in Ontario. The methods change in the cold, but our crews handle commercial roof leak repair in Toronto and across the GTA all year. To cut down on winter leaks, see how to prepare a flat roof for winter. If your building is west of the city, see commercial roof leak repair in Mississauga.
Frequently asked questions
Do you offer 24/7 emergency commercial roof leak repair in Toronto?
OYH Roofing offers 24/7 emergency commercial roof leak repair in Toronto, across the GTA and elsewhere in Ontario. Emergency crews first stop active water entry with a temporary seal, then return for the permanent repair once conditions allow. Call 1-833-775-7663 at any time, day or night.
How much does it cost to repair a leaking flat roof in Toronto?
Repairing a leaking flat roof in Toronto costs $500 to $2,500 CAD per leak on most commercial jobs, as of October 2026. The price depends on the membrane type, roof access and how far water has spread into the insulation. Small patches sit at the low end, and drain or seam repairs with wet insulation removal sit at the high end.
Why does my flat roof only leak during heavy rain?
A flat roof that only leaks during heavy rain usually has a breach that needs water volume or wind direction to reach it, such as a marginal flashing, a slow drain that ponds, or a seam gap. These are still active membrane failures and they get worse each season, so they should be traced and repaired promptly.
Can a commercial roof be repaired in winter in Ontario?
A commercial roof can be repaired in winter in Ontario. TPO and PVC membranes can be heat-welded in cold weather, and modified bitumen and EPDM systems have cold-weather repair procedures. Materials and methods are adjusted below freezing, and a temporary seal may be used during snow or ice until the surface is dry.
Will my insurance cover a commercial roof leak repair?
Whether insurance covers a commercial roof leak repair depends on the cause and on your policy, so no roofer can promise it. Sudden damage from wind, hail or impact is treated differently from wear, age or deferred maintenance. Photograph the damage with dates and ask your roofing contractor for a written cause-of-leak report to document it for your insurer.
How do I know if I need a repair or a full roof replacement?
Get a moisture scan and core cuts before deciding between a repair and a full roof replacement. If wet insulation is confined to the leak zone and the membrane is otherwise sound, repair is usually the right call. If saturation is widespread or yearly repair costs approach 25 to 30 per cent of replacement cost, replacement is the better long-term spend.
Need commercial roof leak repair in Toronto?
Call the 24/7 line and a crew will stop the water first, then trace and fix the leak properly.
Call 1-833-775-7663Request an assessment
Karol Rajkowski
Vice President · OYH Roofing
Karol Rajkowski is Vice President of OYH Roofing, an Oakville-based ICI flat-roofing contractor whose projects include the City of Mississauga building at 3185 Mavis Rd and the Marriott Hotel in Vaughan. Learn more about the OYH team.
Sources
- OYH Roofing project records and repair pricing (October 2026).
- National Roofing Contractors Association (NRCA), guidance on low-slope roof inspection and maintenance.
- Ontario's Building Code, Government of Ontario.
OYH Roofing, 2120 Speers Rd, Oakville, ON L6L 2X8 · 1-833-775-7663 · info@oyhroofing.ca