HOT/General/TBT-HOT-013

Bitumen and Torch-On Roofing

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Bitumen and Torch-On Roofing

Toolbox Talk Record

Ref: TBT-HOT-013  |  Issue: 1  |  Date: March 2026
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What?

  • 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.

Why?

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