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Torch-On Roof Drain Leak Repair in New Westminster

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We got a call about a torch-on flat roof leaking in New Westminster, with water coming into the garage below. On a flat membrane roof, the drains are the number one place leaks start, and that is exactly what we found here.

The problem: the membrane had separated from the drain

The leak was at the roof drain. The torch-on membrane had pulled away from the copper drain flange. We could slide a screwdriver right between the membrane and the flange, which is exactly where the water was getting in and running down into the garage.

Screwdriver wedged between a torch-on roof membrane and the copper drain flange, showing the leak, in New Westminster.
The leak: sliding a screwdriver between the membrane and the copper drain flange showed they had separated. Water was getting in right here and running into the garage below.

What we found when we opened it up

Before doing anything with heat, we embed the granules and prep the surface around the drain so there is no fire hazard when we torch.

Prepping and embedding the granules on a torch-on roof around the drain before cutting, for fire safety, in New Westminster.
Before cutting and torching near the drain, we embed the granules and prep the surface so there is no fire hazard.

Then we cut the membrane open. You could see water sitting between the plies of the roof, and the copper drain flange underneath was wet, confirming the drain was the source of the leak.

Water trapped between the plies of a torch-on roof at the drain in New Westminster.
Once we cut the membrane open, you could see water trapped between the plies of the roof.
Wet copper drain flange under a torch-on roof membrane in New Westminster.
The copper drain flange underneath was wet too, confirming the water was getting in at the drain.

The repair: a new drain and a proper two-ply patch

We cut out the old drain membrane and removed the old drain.

Old drain membrane cut out, about to remove the old drain on a torch-on roof in New Westminster.
The old drain membrane cut out. We are about to remove the old drain itself.

Then we rebuilt it the right way: a new drain, a base layer (the first ply) torched in around it, and a cap sheet (the second ply) on top. That two-ply patch is the same system we use on any roof penetration.

New roof drain installed with the first ply base layer patched around it on a torch-on roof in New Westminster.
The new drain installed, with our first layer, the base ply, patched in around it.
Two-ply torch-on patch, base layer and cap sheet, around a roof penetration in New Westminster.
Our patch build-up on a penetration: the fitting, a torch-on base layer, then a cap sheet on top, the same two-ply system we use at a drain.
Finished two-ply torch-on patch around a new roof drain in New Westminster, no longer leaking.
The second ply, our cap sheet membrane, patched on top. The drain is watertight again.

With the new drain bonded into both layers, the membrane and the drain are one watertight system again, and the leak is gone.

Why flat roof drains leak

On a torch-on or flat membrane roof, the drain is where all the water goes, so it is also where leaks start most often. Over time the membrane separates from the metal drain flange, and once that seal opens, water runs between the plies and into the building, often showing up far from the drain. A bead of sealant will not fix it for long. The lasting repair is to cut it out and rebuild the drain with a proper two-ply patch.

If you have a torch-on or flat roof and you are seeing a leak, especially near a drain, get it looked at before it damages the structure. We repair flat roofs across Greater Vancouver and serve New Westminster and the surrounding area. You can also see the common torch-on flat roof problems we find. Call 778-389-5564 for a free estimate.

Aldergrove Roofing

Concrete tile, torch-on, hidden gutter and commercial roofing specialists serving Greater Vancouver and the Fraser Valley.

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