Flat Roofing and Torch On

Why a flat roof is different

A pitched roof sheds water. Every layer overlaps the one below it and gravity does the work, so a shingle roof can tolerate a detail that is not perfect. A low slope roof holds water instead, sometimes for hours after the rain stops, and the membrane has to be genuinely continuous. There is no second chance built into the system.

That is why flat roofs fail at the edges and the penetrations rather than in the middle. The field of the roof is the easy part. The perimeter, the upstands, the drains and anything poking through it are where the work actually is.

What two ply SBS is

SBS is modified bitumen: asphalt with a rubber in it so it stays flexible instead of going brittle when it is cold. It arrives in rolls and goes down in two layers. A base sheet is laid first, then a cap sheet is torched over it so the two fuse into one skin with the laps staggered, which means no single joint goes all the way through.

The cap carries granules, the same idea as a shingle, which take the sun so the asphalt underneath does not. Done properly it is a long lived roof and it handles standing water in a way nothing else at this price does.

Where flat roofs actually leak

• No fall. If the deck was framed flat and nothing was built in to move water toward a drain, it ponds. Water sitting on a roof finds every weakness it has, and in winter it freezes and works at them.
• Drains and scuppers. Blocked, or set too high so a few centimetres can never leave. A drain that is above the lowest point of the roof is a pond with a plug in it.
• The upstand at a wall. The membrane has to run up the wall and be capped. Stopped short, or finished with sealant instead of metal, and water gets behind it.
• Curbs and penetrations. Vents, units, pipes and skylights each need the membrane carried up and over. This is where most commercial flat roofs let go.
• Laps that were rushed. A torched lap either fused or it did not. Cold weather and a crew in a hurry is how you get one that looks fine and is not.
• Age at the edges. Granule loss, shrinkage and splitting show up at the perimeter first, because that is where the membrane is most worked by heat and movement.

Repair, or replace

A flat roof with one bad detail and a sound membrane elsewhere is worth repairing, and a patch done properly on SBS is a real repair rather than a stopgap. A membrane that has shrunk, gone brittle, or is splitting in more than one place is telling you it is finished, and patching it is money you will not get back.

The way to tell is to get on it and look, which is what the free inspection is for. We photograph what we find, including the parts that are fine, so you are deciding on evidence rather than on our word for it.

Weather, and why timing matters more here

Torch on needs a dry deck. Not damp, dry. Moisture trapped under a membrane has nowhere to go and will blister it from underneath, so the work waits for the weather rather than the other way around.

Between October and December in the eastern valley that is a real constraint, and anyone who tells you otherwise is planning to torch over a wet deck. On a bigger job it can be worked around with tenting and by taking the roof in sections, and we would rather build that into the price and the schedule up front than discover it in November.

Fire, and who is on the roof

Torch on is open flame work on a building. It needs the right setup, the right clearances at anything combustible, and a watch kept after the torches go off, because the fires that happen from this trade almost all start hours later. Kory and Johnny are Red Seal Journeyman Boilermakers and members of Local 280, and that is the standard this work is done to.

Fraser Roofing Ltd. is registered and in good standing with WorkSafeBC and carries $2,000,000 commercial general liability. The clearance letter and the certificate of insurance are on request, from us or from anyone else quoting your flat roof.

What we need to price one

Flat roofs vary more than pitched ones, so a number over the phone would be a guess. What makes the difference is the area, what the deck is, how much upstand there is, how many penetrations, and where the water is meant to go.

On a house or a small building we come and measure. On a commercial build or anything with drawings, send the roof plan and the specification and you will get a real number rather than a range. If your drawings call for an assembly or a guarantee we are not the right outfit for, we will tell you that first instead of quoting around it.

Warranty

Flat roof work carries the same 10 year labour warranty as everything else we do. Material warranties are the manufacturer's and vary by product; we will tell you exactly what the one on your roof covers before you sign anything.