Repairs matched to your membrane
Flat roof repair
A repair is worth doing when most of the roof is still sound. We work out how much of it is, repair what is worth saving and tell you plainly when it is not.
- All common membranes
- Honest repair-or-replace advice
- Starting price listed
Repair is not one job
Fixing a flat roof depends on what the roof is made of. A rubber EPDM patch is a cleaned, primed surface with adhesive and a cover tape or patch. A TPO or PVC repair is heat-welded. Modified bitumen uses a torch-applied patch or, on buildings where flame is unsafe, a cold-applied or self-adhered one. Tar and gravel gets its gravel moved, the felts opened and new plies lapped in.
Using the wrong material is one of the most common reasons repairs fail early. Before anything is patched we identify the membrane. Our pages on EPDM, TPO, modified bitumen and built-up roofing describe each one.
Typical repairs
Patches over punctures and splits
Cut, clean and cover with compatible material, lapped well beyond the damage.
Blister repair
Raised bubbles are cut out, dried and re-laid when the layers underneath are sound. See blisters.
Seam resealing
Open laps are cleaned and rejoined. See flashing and seam repair.
Section replacement
A worn or wet area is cut out, the insulation replaced and new membrane tied into the old.
Edge and parapet work
Metal edging, cap flashings and terminations refastened or replaced.
Alligatoring and surface cracks
Early surface cracking can sometimes be sealed or coated. See cracks and alligatoring.
How a repair job goes
Identify the membrane
Photos or a roof visit tell us what is on the roof and how old it looks.
Map the damage
We mark defects, check for wet insulation and note what else is close to failing.
Written scope
You see what will be repaired, with what, and what is left alone.
Repair
Work is done in dry conditions, with materials suited to the temperature.
Photo record
Before and after photos, so you have a record for your own files.
Repair prices
| Item | Starting price |
|---|---|
| Small leak repair (patch, seam or puncture) | from $350 per repair |
| Flashing repair or replacement | from $500 per repair |
| Skylight, curb or vent reflashing | from $350 per opening |
| Roof drain or scupper repair | from $800 per drain |
Starting prices in CAD before 13% HST, based on typical Ontario contractor rates (mostly Toronto and the GTA). The final price depends on roof size, access, the layers to remove, the membrane, drains and flashings, and is confirmed in your written quote.
When repair stops making sense
A good rule: if repair costs keep climbing, or a third or more of the roof is wet, cracked or blistered, spending on patches is spending on a roof that is finished. Roofs at the end of their life also tend to fail in new places each season. from $8 per sq ft for EPDM, for example, can be a better use of money than a run of repairs. The repair or replace guide has a checklist, and how long a flat roof lasts gives typical ranges.
Questions about flat roof repair
How long should a repair last?
On a sound roof a proper repair should last until the membrane itself wears out. On an old roof it may only buy a season or two, and we will say so.
Can you repair a roof you did not install?
Yes. Most repairs are on roofs installed by someone else. We identify the membrane first and match the repair to it.
Can I walk on the roof to check it myself?
We would rather you did not. Fall risk is real, and foot traffic damages membranes. Photos from a window or a safe hatch are plenty to start with.
Does a repair affect any manufacturer coverage on my roof?
It can. Check your roof documents, and tell us if the membrane has manufacturer coverage so the repair can follow the maker's requirements.
Leak, damage or an old flat roof?
Send a few details and photos. We reply by email with next steps and a written quote.