A commercial flat roof replacement in Calgary usually costs $10 to $20 a square foot, so a 10,000 square foot roof runs roughly $100,000 to $200,000. Replacement means the old roof comes off and a new roofing system goes on, along with any board, insulation and flashing the job needs.
Three commercial roofs we’ve replaced came in at $115,000, $175,000 and $3.5 million. Here’s what sat behind those totals, what the add-ons cost, and how to tell if your roof needs replacing at all.
What does a commercial flat roof cost per square foot in Calgary?
Plan on $10 to $20 a square foot for a full replacement. Size sets the budget, and the condition of the roof decides where you land in that range.
| Roof size | At $10 a sq ft | At $20 a sq ft |
|---|---|---|
| 5,000 sq ft | $50,000 | $100,000 |
| 10,000 sq ft | $100,000 | $200,000 |
| 20,000 sq ft | $200,000 | $400,000 |
Small roofs usually land higher per square foot, because set-up and edge work are spread over less area. Use those figures for a first budget, and get a written quote before you take a number to an owner or a board. A roof looks very different once someone has walked it.
What did three recent Calgary commercial roofs cost?
These are three commercial flat roofs our own crew replaced in Calgary. The totals don’t compare directly, because the jobs differ in size and scope, but each one shows what you’re paying for.
| Job | Building | Total | What shaped the job |
|---|---|---|---|
| Pit Stop Portables | Shop and yard building | $115,000 | Every rooftop unit and vent flashed into the new membrane |
| Northwest Tank Lines | Industrial building | $175,000 | New board, two-ply torch-on on two roof sections, rows of vent stacks |
| Ice River Springs | Working warehouse | $3,500,000 | Tear-off to the steel deck, new insulation, built in sections with the docks open |
Ice River Springs is the clearest example. Trucks used the loading docks every day, so the roof came off and went back on one section at a time, with a scaffold stair tower, a debris chute and a crane set up around them.
What pushes a commercial flat roof to the high end?
Whatever adds labour, material or time pushes the price up. These are the things that move a quote most:
- The deck, once the old roof is off. Wet or damaged sections have to be dealt with before anything new goes down.
- Insulation and board under the membrane.
- Every vent, drain and rooftop unit. Each one has to be flashed into the new roof.
- Access to the roof, including lifts, cranes and where the debris goes.
- A building that has to stay open while the work happens.
- Heavy tear-off, such as tar and gravel or more than one old roof.
On Northwest Tank Lines, the rows of vent stacks mattered because each one is a place a flat roof can leak. That detail takes time, and it’s worth asking how any bid handles it.
What do commercial roof add-ons cost in Calgary?
Most single items cost between $450 and $2,000, and roof hatches and skylights cost several times that. These are our standard service rates, and they cover standard roof access and normal conditions. Lift equipment, specialized access and major repairs are quoted separately.
| Item | Typical cost |
|---|---|
| Vent install | $450 to $1,200 |
| Service line penetration | $450 to $900 |
| Scupper or overflow install | $550 to $1,200 |
| Drain install | $650 to $900 |
| Curb install | $650 to $2,000 |
| Skylight install | $3,500 to $8,500 |
| Roof hatch install | $5,500 to $7,500 |
If an old roof has too few drains or a hatch that needs replacing, a replacement is the easiest time to deal with it, since the roof is already open.
Does the roofing system change the price?
Yes, though the deck and the details often matter just as much. Published Calgary ranges usually put two-ply torch-on (SBS) at the top, with TPO and EPDM a few dollars a square foot lower. Those ranges run a little above ours at the low end, so compare the full scope and not just the per-foot number.
Most of what we install is torch-on, because it’s what we think holds up best here. Two plies give you a second layer of protection, and the granulated surface handles hail and foot traffic well. For the full comparison, read torch-on vs TPO vs EPDM in Calgary.
When is a repair cheaper than a new roof?
A repair is cheaper when the leak is in one spot and the rest of the membrane is sound. Minor commercial leak repairs usually run $600 to $2,800, and flashing or membrane repairs $500 to $2,000. A leak detection inspection runs $500 to $750. Once the membrane is failing in many places, or the same leak keeps coming back, a new roof usually costs less than chasing leaks.
These are the signs we look for before we say replace:
- Blisters, ridges or cracks in the membrane.
- Granule loss, curling or cupping.
- Water ponding on the roof.
- Open laps and worn sealant.
- Impact damage.
Soft or spongy spots underfoot are another warning, because they often mean wet insulation. Not sure which side you’re on? A commercial roof inspection answers that. Water coming in right now? Start with flat roof repair.
How does Calgary weather affect a commercial roof budget?
Calgary is hard on flat roofs, so plan the budget around hail and melt. The City of Calgary reports a 30-year average of 128 freeze-thaw cycles a year, and a flat roof faces straight up into every hailstorm.
Snow melts in a warm spell and refreezes overnight, often at the drains and edges where water collects. That’s why blocked drains and ponding turn into repair bills here. Repairs after wind or rain expose a weak point usually run $3,000 to $15,000, so keep the drains clear and get the roof checked after a big storm. Roofers also book up quickly after a major hailstorm, so a planned replacement is easier to schedule before one hits.
Winter doesn’t have to stop a job, either. We put the Propak roof on through the snow, one section at a time.
How should you compare commercial roof quotes?
Compare the scope line by line, because the lowest total often leaves something out. Ask each roofer to write down the system, the number of plies, the insulation, how every penetration gets flashed, what happens if the deck is bad, and whether a permit is needed. Ask for proof of WCB coverage and liability insurance too.
Our quotes are written and itemized, so an owner or a condo board can read them. We install torch-on, TPO and EPDM, and flat and commercial roofs carry a 10-year workmanship warranty.
If you’re budgeting years ahead for a reserve fund or capital plan, a free roof assessment gives you a photo report and a list of what to address, plan for or monitor. Maintenance plans start at $0.18 a square foot.
Common questions
How long does a commercial flat roof replacement take?
Other Calgary roofers publish one to three weeks of site work for small and medium roofs, and two to four months from first call to finished roof. Big or phased jobs take longer, so ask for dates in writing.
Can you reroof over an existing flat roof?
Sometimes. A recover can cost less up front, but only if the deck and insulation underneath are sound and dry. If they’re wet, going over them traps the problem. On Ice River Springs, the old roof came off down to the steel deck.
Can a building stay open during a roof replacement?
Often, yes. Working in sections keeps most of the building covered. Ice River Springs kept its loading docks running for the whole job.
Does insurance cover a commercial flat roof?
Often for sudden storm damage, and not for age or wear. Policies vary, so check yours and take dated photos before anything is repaired. We’ve documented more than 1,200 hail claims since 2014, and our hail damage page covers how a claim works.
What does an emergency commercial roof leak cost?
An emergency callout to locate and control an active leak usually runs $1,500 to $5,000 or more. After-hours work is often 50% higher.
We replace flat roofs on business, condo and multi-family buildings across Calgary, and every quote comes after we’ve seen the roof. See commercial roofing in Calgary or call 403-608-9933.
