Roofing systems · EPDM
EPDM Roofing Ottawa
EPDM is a synthetic rubber single-ply membrane, widely used on low-slope roofs in cold climates. Here's how it works, where it fails and what to consider in Ottawa.
The short answer
EPDM (ethylene propylene diene monomer) is a flexible rubber membrane, usually black, installed in large sheets that are fully adhered, mechanically fastened or ballasted. It stays flexible at low temperatures and has a long track record on low-slope roofs. Its weak points are usually seams and flashings, which rely on tapes and adhesives that must be installed correctly. We repair existing EPDM roofs and include it among the options when a roof is replaced, after an assessment.
How EPDM performs in Ottawa's climate
Ottawa sees long cold spells and many freeze-thaw cycles. EPDM's flexibility in the cold is one of its strengths: the membrane accommodates building movement without becoming brittle as quickly as some other materials. Its dark surface absorbs summer heat, which has little winter benefit but can raise roof temperatures in summer.
Seams, flashing, drainage and insulation
Seams
EPDM sheets are joined with seam tape and primer, or adhesives on older roofs. Seam quality depends on clean, primed surfaces and proper pressure. Older adhesive seams can open with age.
Flashing
Walls, curbs and penetrations are flashed with EPDM flashing and pre-formed accessories. Base flashings at walls are a common leak point when snow drifts and melts against them.
Drainage
Ponding water accelerates wear on any membrane and adds weight. Drains, crickets and tapered insulation should move water off the roof.
Insulation
On a replacement, the insulation layer under the membrane can be upgraded. Wet insulation found during removal should be replaced, not covered.
Repairing EPDM: what's compatible
EPDM is repaired with EPDM-compatible primers, cover tapes and patches. Asphalt-based patching products and many generic sealants are not compatible and can make a proper repair harder later. Older EPDM may need thorough cleaning before a patch will bond. If the membrane has shrunk and is pulling away from walls and edges, repairs become less effective.
Pros and cons
- Pro: flexible across a wide temperature range
- Pro: relatively straightforward to repair with compatible materials
- Pro: long history of use on low-slope roofs
- Con: seams depend on tape or adhesive quality
- Con: dark surface absorbs summer heat
- Con: can be punctured by sharp debris or foot traffic without protection
Quote cost factors
Size and shape of the roof; whether existing roofing must be removed; the condition of the deck; insulation type and thickness; the number of drains, penetrations and curbs; parapet and wall flashing height; access and hoisting; and the season. We don't publish flat prices because these vary widely from roof to roof.
Maintenance
Keep drains clear, keep foot traffic to protected routes, and have seams and flashings checked periodically by a professional — especially after winter. Small open laps are inexpensive to fix early.
References: City of Ottawa — Do I need a building permit? · NRC Energy RCI
Frequently asked questions
Can EPDM be patched with roofing tar?
No. Asphalt-based products aren't compatible with EPDM. Repairs should use EPDM-compatible primers and tapes.
Is EPDM a good choice for Ottawa?
It's widely used in cold climates and stays flexible in winter. Whether it suits your roof depends on drainage, details, use and budget, which an assessment can clarify.
Do you hold manufacturer certifications for EPDM?
We don't claim manufacturer certifications on this site. Ask about product, warranty and installation details when you receive a written scope.
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