Flat roof repair · Calgary
Flat roof repair in Calgary, when a repair will actually hold
I'm Stivi of Stivi Roofing, and I repair flat roofs in Calgary when the leak comes from a seam, a wall corner, a curb or a drain and the rest of the membrane is still sound. If the membrane is cracked across the whole roof or the insulation under it is wet, a repair won't hold, and I'll tell you it's time for aflat roof replacement.
- Open seams re-bonded or patched
- Stucco wall corners re-flashed
- A straight repair or replace answer
Problem 1
Why do flat roof seams open up?
Flat roof seams open up because every lap between two sheets of membrane moves with the roof. Calgary swings from frozen to thawed many times each winter, and the membrane shrinks and stretches with it. Over the years, the bond at the lap weakens and the edge of the top sheet curls up.
An open seam lets water run sideways under the membrane. On a flat roof that water has nowhere to drain, so it soaks into the insulation below, often metres away from where it shows up on your ceiling.
Problem 2
Why do flat roofs leak where they meet a stucco wall?
Flat roofs leak where they meet a stucco wall because the membrane has to turn a sharp corner there and the house and the roof move differently. The membrane cracks at the fold, and the joint between the top of the membrane and the stucco opens up.
Inside corners are the worst spot: two walls, one floor, and a fold in three directions. When a corner like that was finished with a bead of caulking instead of a metal counterflashing over the top edge of the membrane, the caulking is the only thing keeping water out, and it gives up first.
Problem 3
Why do vents, skylight curbs and drains leak on a flat roof?
Vents, skylight curbs and drains leak on a flat roof because each one is a hole in the membrane, and the flashing around it is a separate piece that has to be sealed into the roof. A curb is the raised wood frame a skylight or vent sits on. When the membrane around the curb is not carried up its sides and covered at the top, water gets behind it.
Drains fail at the clamping ring or where the membrane laps into the drain bowl. A drain that leaks is also a drain that stops draining well, which leads straight to the next problem.
Problem 4
What does ponding water do to a flat roof?
Ponding water ages a flat roof faster than anything else. Water that stands for days after a rain keeps the membrane wet, finds every weak lap, and freezes into ice that pulls on the seams. The sun bakes the ring of dirt it leaves behind into the surface.
Ponding happens when the deck has sagged, the insulation has crushed, or the roof was built without enough slope to its drains. A patch in a pond is the shortest-lived repair on a flat roof.
The deciding question
Can a flat roof be repaired, or does it need replacing?
A flat roof can be repaired when the leak is at a joint and the insulation under the membrane is dry. It needs replacing when the insulation is wet over a wide area, because wet insulation never dries out under a membrane: it rots the deck, freezes, and lifts any patch you put over it.
So the condition of the layers underneath decides it, not the age of the roof or how the top looks. I check the insulation around every leak before I quote. If it's dry, you get a repair. If it's soaked, I'll show you, and the honest answer is a new flat roof from the deck up.
Fix 1
How I repair open seams on a flat roof
I repair an open seam on an SBS flat roof by drying and cleaning the lap, heating it, and bonding the top sheet back down. Where the edge has curled or cracked, I torch a strip of new SBS cap sheet over the full length of the seam so it laps well past the damage on both sides.
I check every other seam on the roof while I'm up there. One open seam usually means others are close behind, and it costs far less to close them in the same visit.
Fix 2
How I seal a flat roof to a stucco wall
I seal a flat roof to a stucco wall by cutting out the cracked membrane at the corner, reinforcing the inside corner with a pre-formed or hand-cut SBS piece, and running the new membrane up the wall. A metal counterflashing then covers the top edge of the membrane so water runs down the wall and over the membrane, never behind it.
Caulking at that joint becomes a weather seal on the metal, not the only thing between your wall and the rain.
Fix 3
How I re-flash curbs, vents and drains on a flat roof
I re-flash a curb, vent or drain by stripping the old flashing back to clean membrane, then wrapping the curb or collar with new SBS base and cap sheet that runs up its sides and laps onto the roof. On drains, I reset the membrane into the drain bowl under the clamping ring.
If you have a leaking skylight rather than a curb problem, my skylight repairpage covers when the unit itself needs replacing.
Fix 4
How I deal with ponding water on a flat roof
I deal with ponding water by fixing the reason the water stays. A blocked or leaking drain gets cleared and re-flashed. A small low spot near a drain can be built up under a new patch. When the whole roof ponds because the deck sagged or the insulation crushed, the real fix is rebuilding the slope during a replacement.
I won't sell you a patch in the middle of a pond. It's money spent on a repair I already know won't last.
Next step
Flat roof repair in Calgary, or a straight answer that you need more
Stivi Roofing repairs flat roofs in Calgary at the seam, wall corner, curb or drain that leaks, as long as the insulation under the membrane is dry. When it isn't, I'll show you why a repair won't hold and quote atwo-ply torch-on SBS replacement instead.
Send me photos of the roof and the ceiling where the water shows up, and I'll take it from there.
Flat roof repair questions from Calgary homeowners
- How do I repair a flat roof without replacing it?
- Repair the joint that leaks and leave the sound membrane alone. On an SBS flat roof I clean and prime the area, then torch a new SBS patch over the open seam, crack or corner so it laps well past the damage on every side. That only works when the insulation under the patch is dry.
- Can I patch a flat roof myself?
- You can slow a leak with roofing cement and a membrane patch from the hardware store, and that is a reasonable thing to do until a roofer gets there. It is a temporary fix: cement on top of a flat roof dries and cracks, and it hides the open lap underneath instead of closing it.
- How long does a flat roof repair last?
- A seam or flashing repair made with SBS membrane lasts as long as the membrane around it, provided the insulation under it is dry and water drains off that spot. A repair over wet insulation fails much sooner, because the trapped moisture lifts the new patch from below.
- Can you repair a flat roof in winter in Calgary?
- I need a dry, frost-free surface to torch SBS membrane, so I schedule permanent flat roof repairs on dry days. Calgary gets plenty of those in winter between snowfalls. When the roof is wet, a temporary patch holds the water out until the surface is dry enough to torch.