Rubber membrane
EPDM roofing
EPDM is a synthetic rubber sheet supplied in wide rolls, so a typical house roof can be covered with very few seams. It stays flexible in cold weather and is one of the easier flat roofs to patch.
- Rubber membrane
- Few seams
- Easy to patch
What EPDM is
EPDM stands for ethylene propylene diene monomer. In plain terms it is the same family of rubber used in car door seals. It comes in rolls that can be 10 feet wide or much wider, which is why a garage or addition roof can often be one continuous sheet with no seam in the middle.
Most EPDM is black. White versions exist but are less common in Ontario. EPDM roofs commonly last 20 to 30 years when drains are kept clear and the flashings are looked after. Replacement is priced from $8 per sq ft.
How EPDM is attached
Fully adhered
The sheet is glued to the insulation or cover board over the whole surface. Quiet, tidy and resistant to wind lift. This is the usual method for houses.
Mechanically fastened
The sheet is held by plates and screws along seams. Faster over large areas, but the membrane can flutter in wind, and fasteners need correct spacing.
Ballasted
Loose stone or pavers hold the sheet down. It adds weight, so the structure must carry it. Seen on older commercial roofs and some roofs with pavers for foot traffic.
Seams, corners and where EPDM leaks
The field of an EPDM sheet rarely fails on its own. Trouble tends to start at seams that were joined with tape or splice adhesive, and at inside and outside corners, pipe boots and curbs where pre-molded or hand-made flashings are used. These are small areas, which is why most EPDM repairs are small too.
Shrinkage is a known issue with older EPDM: over the years the sheet can pull back from a parapet wall or curb, leaving an unsupported flashing that opens up. If you see the membrane pulling away at a wall, have it looked at before the next freeze–thaw cycle.
Pros and cons in an Ontario climate
Flexible in the cold
EPDM does not get brittle in a hard January the way some other membranes can, so it handles freeze–thaw swings well.
Simple to repair
A patch of cured or uncured rubber and primer fixes most punctures. Compare this with rolls that need open flame or welding equipment.
Large sheets, fewer joints
Fewer seams means fewer places to leak. The weak points move to the edges and penetrations.
Dark colour
A black roof absorbs summer heat. On a house this matters little; on a building with rooftop air conditioning it can add cooling cost.
Punctures and oil
Sharp objects, dropped tools and some oils and greases damage EPDM. It is not the best choice under a kitchen exhaust.
Seams depend on workmanship
Glued seams need clean surfaces and dry weather. Bad seam work shows up two or three winters later.
How an EPDM repair works
Find the actual source
Water often travels under a membrane before it appears inside. We trace it from the stain back to the nearest seam, penetration or low spot.
Clean and prepare
The area around the damage is dried and scrubbed back to bare rubber so the repair material bonds.
Patch or reflash
Small holes get a primed patch. Failed corners and curbs are reflashed with new flashing material rather than smeared with sealant.
Check the surroundings
We look at drains, seams and edges nearby, because a leak in one place often points to similar wear in another.
EPDM pricing
| Item | Starting price |
|---|---|
| EPDM roof replacement | from $8 per sq ft |
| Small leak repair (patch, seam or puncture) | from $350 per repair |
| Flashing repair or replacement | from $500 per repair |
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.
EPDM questions
Can EPDM be repaired in winter?
Temporary protection is possible in cold weather, but adhesives and tapes need dry, reasonably warm surfaces to bond. Permanent repairs are usually scheduled for a milder, dry day.
Why is there a seam tape strip on my EPDM roof?
That is where two sheets overlap. A well-made seam is fine, but if the tape edge is lifting or the lap feels loose, it needs attention.
Is EPDM good for a roof with a deck on top?
It can work under pavers or wood decking if the roof is protected with a slip sheet and drainage mat. See rooftop deck waterproofing for options.
Leak, damage or an old flat roof?
Send a few details and photos. We reply by email with next steps and a written quote.