HOT/General/TBT-HOT-013

Bitumen and Torch-On Roofing

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Torch-on roofing involves applying bitumen felt membranes to flat roofs using a gas-fired blow torch.
The flame softens the bitumen underside of the membrane, bonding it to the prepared roof surface.
Torch temperatures exceed 1,000°C and the molten bitumen surface reaches approximately 200°C.
A hot works permit is mandatory for all torch-on roofing operations on construction sites.
Fire risk is significant — the flame can ignite insulation, timber decks, and debris on the roof.
Bitumen fumes contain polycyclic aromatic hydrocarbons (PAHs) that are respiratory irritants and carcinogens.
Working on flat roofs creates fall-from-height risks at unprotected roof edges and through fragile surfaces.
LPG cylinders powering the torch must be properly secured, stored, and transported on the roof.
A fire watch period of at least 60 minutes after the last torch pass must be maintained.
Solvent-based primers applied before the membrane are highly flammable and must fully flash off first.

Fire hazard	Torch-on roofing uses open flame near combustible insulation and primers — roof fires occur frequently during installation.
Burn injuries	Molten bitumen and torch flames cause severe burns to skin, hands, and through clothing.
Fume exposure	Bitumen fumes irritate the respiratory system and contain PAHs linked to cancer with chronic exposure.

Don't

Obtain a hot works permit before starting any torch-on roofing operation
Clear the roof of combustible debris and materials before beginning torch work
Allow solvent-based primers to fully flash off before applying the blow torch
Keep a fire extinguisher within immediate reach of the operative using the torch
Wear heat-resistant gloves, long sleeves, and appropriate RPE for bitumen fumes
Maintain the fire watch for at least 60 minutes after the last flame application
Secure LPG cylinders upright on the roof and check hose connections before igniting
Install edge protection on all open roof edges before starting any roofing work
Brief the roofing team on the fire response procedure and extinguisher locations
Check for fragile roof lights and cover or protect them before working on the roof

DON'T use a blow torch without a valid hot works permit in place
DON'T apply flame before the primer coat has fully flashed off and dried
DON'T leave the blow torch alight and unattended on the roof at any time
DON'T store more LPG cylinders on the roof than needed for the current shift
DON'T work at roof edges without edge protection or fall restraint systems
DON'T ignore bitumen fume exposure — wear RPE and maintain good ventilation
DON'T end the fire watch early — fires can ignite well after the torch is extinguished
DON'T carry lit torches up or down ladders or across the roof carelessly
DON'T heat the membrane excessively — overheating creates more fume and fire risk
DON'T step on freshly torched bitumen — it is molten and will burn through footwear

See also: Hot Works Permit Requirements | Flat Roof Membrane Installation

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