Torch-on roofing · new roofs, replacement and repairs
Torch-on roofing: new roofs, replacement and repairs
Torch-on roofing is a modified-bitumen membrane system, heat-welded in place. We assess the existing roof and the deck before we price anything, and if a liquid-applied restoration would do the job instead, we will say so.
What torch-on roofing is
Modified bitumen, welded to the roof and to itself.
A torch-on roof is built from rolls of modified-bitumen membrane. Each sheet is heated with a torch as it is unrolled, so its underside softens and bonds to the layer below, and its laps are fused to the next sheet. The result is a continuous sheet roof, with the flashings at parapets, curbs, drains and penetrations formed as part of it.
The assembly for each roof is set after the assessment: the membranes, the number of layers, any insulation and the manufacturer. It is written into the proposal, so you know exactly what is going on your roof before work starts.
When it fits
Where a roof needs replacing, or a new roof is going on.
| The roof | What it usually needs |
|---|---|
| Roofing failed across the field: wet or unbonded, widely blistered or split | Replacement: the old roofing off to the deck, the deck repaired, a new torch-on roof |
| A new roof deck | A new torch-on roof to the specified assembly, or, on a new concrete deck, the RMS liquid-applied membrane |
| Local damage on an otherwise sound torch-on roof | A repair of the damaged area, its laps and its flashings |
| A sound roof leaking at seams, flashings or drains | Repairs, or a liquid-applied restoration of the whole roof after a test patch |
| A roof that carries regular foot traffic or parking | A traffic membrane rather than a roofing membrane: see parkade waterproofing |
Assessing the existing roof
What we check before a torch goes anywhere near it.
| Where we look | What we are looking for |
|---|---|
| The field | Blisters, splits, bare or worn areas, soft spots underfoot |
| Laps and seams | Open, lifting or wrinkled laps |
| Flashings | Open, slipped or cracked flashings at parapets, walls and curbs |
| Drains and scuppers | Blocked, damaged or set high, with water standing round them |
| Penetrations | Pipes, vents and supports, and how each one is sealed |
| Drainage | Ponding after rain, and where the slope has been lost |
| The deck | Its condition wherever it can be seen, from openings or from below |
| Inside | Stains and drips, and how soon after rain they show |
Where the roofing is wet or unbonded across the field, replacement is the honest answer. Where it is sound, a repair may be enough, or the whole roof may be restorable with a liquid-applied membrane, which an adhesion test patch confirms. For a first look of your own, use our flat roof inspection checklist.
Details and drainage
Most leaks start at an edge, not in the field.
Parapets and walls, the curbs under rooftop units, drains and scuppers, and pipe and vent penetrations are where a flat roof changes direction or material, and where most leaks begin. On a replacement, every one of them is rebuilt with the new roof; on a repair, they are usually the first thing we look at. Expansion and movement joints get their own detail, which is the work on our expansion joints page.
A replacement is also the time to deal with water that sits on the roof. How a roof drains is set by its design, and any correction to the slope or the drains is agreed in the scope before the new roof goes on.
Scope and schedule
What sets the price and the timing.
The size of the roof; what comes off on a replacement; the condition of the deck once it is exposed; how much detail work there is at parapets, curbs, drains and penetrations; rooftop equipment that has to be worked round; how materials get onto the roof; and what is going on in the building below. We do not give a fixed price or a duration before the roof has been inspected.
Weather sets the rest. Torch-on roofing goes on in dry weather, and because it is open-flame work, the hot-work plan for the building, including where the torch must not be used, is agreed before work starts.
Torch-on or liquid-applied
Neither is the better roof everywhere.
Torch-on replaces roofing that has failed. A liquid-applied ResinTech membrane restores roofing that is still sound, without taking it off and without an open flame. Which one your roof needs is decided by its condition, and where both are possible, the fair comparison is two scopes priced against the same inspection. The flat roofing page compares the two side by side.
Questions we get asked
Torch-on roofing FAQs
What is torch-on roofing?
A flat-roof system built from rolls of modified-bitumen membrane. Each sheet is heated with a torch as it is laid, so it bonds to the layer below, and its laps are fused to the next sheet. The flashings at parapets, curbs, drains and penetrations are formed as part of the roof.
Do you repair torch-on roofs, or only replace them?
Both. Local damage on an otherwise sound roof, such as an open lap, a blister or a failed flashing, is repaired. A roof whose roofing has failed across the field is replaced. The assessment decides which.
Can our existing torch-on roof be coated instead of replaced?
Possibly. If the existing roofing is sound, dry and firmly bonded, and the roof drains, it may be restored with the ResinTech RMS liquid-applied membrane. An adhesion test patch decides, and the existing roof type is confirmed with ResinTech first.
How is the torch work managed on an occupied building?
As hot work, planned for the building before work starts: where the torch is used, where it must not be, and how the details near anything combustible are finished. Tell us how the building is used, and about any fire-safety requirements of your own, at the assessment.
How long does a torch-on replacement take?
It depends on the size of the roof, the layers that come off, the condition of the deck, the amount of detail work and the weather. We give a schedule with the written proposal, not before the roof has been inspected.
Which membranes do you use?
The assembly for each roof, meaning the membranes, the number of layers, any insulation and the manufacturer, is set after the assessment and named in the written proposal, so you know what is going on your roof before work starts.
How is a torch-on roof priced?
After an inspection. The size of the roof, what has to come off, the condition of the deck, the flashings and penetrations, rooftop equipment and access set the price, so we do not quote a blind rate per square foot.
Roof assessment request
Tell us about the roof.
The more of this you fill in, the more useful our first reply. If water is coming in right now, call (604) 968-2040 instead — that is faster than any form.
Keep reading
Related pages
Liquid-applied restoration
The ResinTech RMS membrane over a sound existing roof or a new concrete deck.
Learn more →Restore or replace
The four questions that decide whether a commercial flat roof can be restored.
Learn more →Roof assessments
Send us the roof. We’ll tell you what it needs.
Photographs and a rough area are enough to start. We inspect the roof and the deck and tell you whether it needs a repair, a restoration or a new roof.
Main (604) 968-2040
Second (604) 230-0256
estimating@westpacificcoatings.com