Flat Roofing
Flat Roofing in Calgary
Flat roofs are where the details get rushed, and rushed details are why Calgary buildings leak. I have been repairing and replacing flat roofs here since the early 2000s, and I still climb every one myself before I write a number.
A flat roof does not forgive a bad detail
On a sloped roof, the kind covered by our Calgary roof repair services, gravity moves water off even when the flashing is mediocre. On a flat roof, water sits, and it finds the one seam, the one drain, the one parapet flashing that somebody rushed.
That is why I price flat work off the details, not off the square footage alone.
What counts as a flat roof
A flat roof is a low-slope roof built as a single continuous waterproof membrane rather than as overlapping shingles. No flat roof is actually flat. The Alberta Building Code requires a minimum slope of 1:50 (2%, or about 1/4 inch per foot) so water drains rather than ponds. That slope comes from tapered insulation or from the framing itself.
Calgary flat roofs show up on four building types: modular and mobile homes, mid-century bungalow additions and garages, modern infills in Altadore, Marda Loop, and Bridgeland, and commercial buildings across the city: strip malls, warehouses, restaurants, and office blocks.
Flat roof repair or replacement: how I decide
I replace a flat roof when water already reached the insulation. I repair one when it has not. Core samples decide that, not how the membrane looks from the ladder.
I recommend repair when
- The membrane failed at a specific detail: a seam, a drain, a curb, a parapet, a vent boot.
- Core samples come back dry, meaning the insulation below is still intact.
- The field membrane holds elasticity and shows no widespread cracking or alligatoring.
- The roof is under 12 years old and this is the first failure.
I recommend replacement when
- Core samples come back saturated. Wet insulation never dries under a membrane. Saturated insulation rots the deck below it and loses most of its R-value, so the heat you pay for leaves through the roof.
- The membrane blisters or splits across the whole field, not at one detail.
- The roof already carries two membrane layers. Most flat roofing manufacturers void warranty coverage past two layers, and a third layer over wet insulation traps the problem permanently.
- Ponding water sits longer than 48 hours after rain, which means the slope itself failed.
I cut core samples on any flat roof over 10 years old before quoting a replacement. Guessing at insulation condition is how homeowners get sold a $20,000 roof they did not need, or a $3,000 patch over a rotted deck.
The flat roofing systems I install in Calgary
Four membrane systems handle almost every Calgary flat roof. Each solves a different problem, and I match the system to the building rather than installing the same thing everywhere.
Torch-on SBS
My default for Calgary residential
SBS is styrene-butadiene-styrene modified bitumen: asphalt with a rubber polymer blended in. My crew torch-applies it in two plies from rolls. The rubber keeps the membrane flexible in deep cold (SBS cap sheets are cold-flex tested to −30 °C under CSA A123.23), where unmodified asphalt would crack.
Two-ply torch-on SBS is the system I install most often on Calgary homes, garages, and additions. It handles our freeze-thaw cycle, absorbs hail impact, and repairs cleanly years later: a torch and a patch, no proprietary tooling. I install IKO Torchflex as the standard grade and Soprema Sopralene where the client wants the heavier cap sheet and the longer manufacturer warranty. Granulated cap sheets come in several colours if the roof is visible from a deck or a second storey.
EPDM rubber
The modular and low-traffic choice
EPDM is ethylene propylene diene monomer, a single-ply synthetic rubber membrane. My crew rolls it out in sheets up to 50 feet wide and either fully adheres it or mechanically fastens it. Fewer seams means fewer failure points.
EPDM stays flexible far below any temperature Calgary produces (the membrane’s brittleness point sits near −45 °C under ASTM D746), so our chinook cycle does not fatigue it the way it fatigues rigid membranes. EPDM is the system I recommend for modular and mobile homes, where a full replacement on a typical 1,000 to 1,400 square foot roof runs $18,000 to $22,000. The trade-off is colour: standard EPDM is black, so it absorbs summer heat rather than reflecting it.
TPO
The reflective commercial membrane
TPO is thermoplastic polyolefin, a single-ply membrane with heat-welded seams that fuse into a continuous sheet rather than relying on adhesive. TPO comes in white, which reflects solar heat and cuts cooling load on buildings running rooftop HVAC all summer. I install TPO on Calgary commercial buildings, warehouses, and larger flat-roofed infills where energy performance and a long service life justify the cost. Heat-welded seams also make TPO the more reliable choice on roofs with heavy penetration counts.
PVC
For restaurants and industrial exposure
PVC is polyvinyl chloride, a single-ply membrane that also welds at the seams and resists grease, animal fats, and chemical exposure far better than TPO does. Restaurant kitchen exhaust can break down an ordinary membrane in five to ten years. PVC holds up under it. If your building runs commercial kitchen exhaust, industrial venting, or chemical processes, PVC is the system I quote. It costs more than TPO up front and outlasts TPO in those conditions.
Which flat roofing system suits your building
Service life assumes proper installation and annual maintenance. A flat roof that nobody inspects fails a decade early, regardless of which membrane sits on it.
| System | Best for | Seams | Service life | Notes |
|---|---|---|---|---|
| Torch-on SBS | Calgary homes, garages, additions | Torch-fused, 2-ply | 20–30 years | Easiest to repair; handles freeze-thaw and hail |
| EPDM rubber | Modular homes, low-traffic roofs | Adhesive / tape | 20–30 years | Cold-flexible to −45 °C; black absorbs heat |
| TPO | Commercial, warehouses, infills | Heat-welded | 15–25 years | White and reflective; lowers cooling load |
| PVC | Restaurants, industrial exposure | Heat-welded | 20–30 years | Resists grease, fats, and chemicals |
Why flat roofs fail in Calgary
Calgary punishes flat roofs in four specific ways, and knowing which one hit your building tells me what to fix.
Freeze-thaw cycling
Chinooks swing rooftop temperatures across the freezing point dozens of times each winter. Every cycle expands and contracts the membrane. Brittle materials split; that is why membrane selection matters more here than in milder cities.
Ponding water
Water that sits longer than 48 hours accelerates membrane breakdown and adds serious weight: a pond one inch deep across 1,000 square feet weighs over 5,000 pounds. Ponding almost always traces back to blocked drains, crushed insulation, or a deck that settled.
Hail
The August 5, 2024 Calgary hailstorm produced $3.29 billion in insured damage and over 130,000 claims (CatIQ, revised August 2025). Hail bruises a flat membrane the same way it bruises a shingle, and the damage often does not leak until the following spring.
Failed penetration flashings
Vents, drains, curbs, skylights, and HVAC units cause most flat roof leaks. The field membrane usually survives intact. I check penetrations first on every service call.
I also repair leaking skylights as part of the same visit, since a skylight curb on a flat roof is just another penetration that has to be flashed correctly.
Residential and commercial flat roofing
EZ Roof Repair handles both. Residential flat roofing covers modular homes, garages, additions, and modern infills, and it runs on torch-on SBS or EPDM in most cases. Commercial flat roofing covers strip malls, warehouses, restaurants, and office buildings, and those usually run TPO, PVC, or two-ply SBS depending on rooftop equipment and exposure.
Commercial work starts at $1,200 per square (100 square feet). I schedule commercial tear-offs around your operating hours so your tenants and customers keep their access.
Plenty of Calgary properties carry both roof types: a sloped shingle roof over the house and a flat membrane over the addition, the garage, or the dormer. I install both, and I detail the transition myself, because the wall-to-roof tie-in between a shingle field and a membrane is where mismatched trades leave a gap. If your property needs the sloped section done at the same time, see complete roof replacement.
Keeping a Calgary flat roof alive
A flat roof needs two visits a year to reach the top of its service life. Here is what I check, and what you can check yourself from a ladder.
Clear the drains and scuppers
Every spring and every fall. A single plugged drain creates the ponding that ends the membrane early.
Walk the perimeter flashings
Parapet caps and counter-flashing loosen under chinook expansion. Loose metal lets wind-driven rain behind the membrane.
Inspect after every hail event
Bruising on a membrane looks like nothing from the ground. Document it the same season so the damage stays inside your policy’s reporting window.
Keep foot traffic on walk pads
HVAC service techs puncture more Calgary flat roofs than weather does. Walk pads cost a fraction of a membrane repair.
I offer scheduled maintenance visits on commercial buildings, with a written condition report and photos after each inspection so you have documentation for your owner or your insurer.
Recent flat roofing work in Calgary
Real jobs, photographed on site. Click any photo to enlarge it.
Who does the work
Property managers and general contractors can request current certificates of insurance and WCB clearance before we mobilize. My own crew performs every flat roof. EZ Roof Repair does not subcontract torch work, because hot work on an occupied building is not something I hand to a stranger. Every flat roof replacement carries a 10-year written labour warranty, detailed on our warranty page.
EZ Roof Repair installs and repairs flat roofs across Greater Calgary, Airdrie, Cochrane, Okotoks, Chestermere, and Strathmore. Free on-site assessments, including core sampling on replacement quotes.
- Alberta corporation
- #2023600071, incorporated July 6, 2021
- Liability insurance
- $2,000,000 Commercial General Liability, active
- WCB-Alberta
- Active account #9372476 (Residential Roofing) since April 14, 2022
- City of Calgary licence
- #16375420
Flat roofing FAQs
How much does flat roof repair cost in Calgary? +
Most flat roof repairs run $800 to $4,000, depending on whether we are patching one detail or rebuilding a section. I quote after inspecting the roof, and the quote is the invoice.
How long does a flat roof last in Calgary? +
A properly installed SBS, EPDM, TPO, or PVC roof lasts 20 to 30 years here. Annual inspection and drain clearing is what gets you to the top of that range instead of the bottom.
Can you repair a flat roof in winter? +
Yes. Torch-on SBS patches apply year-round, and I do emergency flat roof repairs 24/7 through Calgary winters. Full replacements go better in shoulder season, so I schedule those for spring or fall unless the roof is actively failing.
Which is better for a Calgary flat roof, SBS or EPDM? +
SBS suits most Calgary homes because it repairs easily and stands up to hail and foot traffic. EPDM suits modular homes and low-traffic roofs because it has fewer seams and exceptional cold flexibility. I recommend based on your deck, your access, and how the roof gets used.
Do you do commercial flat roofing? +
Yes: strip malls, warehouses, restaurants, and office buildings, in TPO, PVC, or two-ply SBS. Commercial pricing starts at $1,200 per square.
My building has a flat section and a sloped section, can you do both? +
Yes, and doing both together is usually cheaper than two mobilizations. The tie-in between a shingle field and a flat membrane is the detail that leaks when two different trades handle it. See roof replacement in Calgary for the sloped side of the work.
Can a flat roof be replaced without tearing off the old one? +
Sometimes, if core samples come back dry and the roof carries only one existing layer. If the insulation is wet, a recover traps the moisture and the deck rots underneath. I cut cores before recommending it.
Get a flat roof assessment
I inspect the roof, cut cores where they are needed, and give you a written number that does not move. Answered 24/7 for flat roof emergencies. - Sokol Preka, Owner & Operator, EZ Roof Repair Inc.
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