NRCA is concerned with fire safety and prevention during the application of torch-applied polymer-modified bitumen sheet products—especially over combustible substrates—but believes torch application can be safe if the roof membrane and construction details are properly designed and installed with consideration for fire and safety techniques.
The specific flashing backer intended and its configuration should be included in designs and consistent with the membrane manufacturer's roof system requirements. Construction details designated as "MB(T)-" in Chapter 10—Construction Details of The NRCA Roofing Manual: Membrane Roof Systems illustrate some typical CERTA-compliant flashing configurations. The following construction details for polymer-modified bitumen membranes depict membrane flashing configurations over combustible flashing substrates NRCA considers appropriate.
MB(T)-1 systems
- MB(T)-1—Base Flashing at Parapet Wall With Metal Coping (Torch-applied Flashing Systems)
- MB(T)-7—Base Flashing at Roof-to-wall Expansion Joint (Torch-applied Flashing Systems)
- MB(T)-8—Base Flashing at Expansion Joint With Metal Cover (Torch-applied Flashing Systems)
- MB(T)-9—Base Flashing at Area Divider in Roof System (Torch-applied Flashing Systems)
- MB(T)-10—Base Flashing at Equipment Support Curb (Torch-applied Flashing Systems)
- MB(T)-13—Base Flashing at Wood Curb (Torch-applied Flashing Systems)
- MB(T)-14—Base Flashing at Structural Member Through Roof Deck (Torch-applied Flashing Systems)
- MB(T)-15—Base Flashing at Sheet-metal Enclosure for Piping Through Roof Deck (Torch-applied Flashing Systems)
- MB(T)-16—Base Flashing at Stack Vent With Curb [Hot or Cold] (Torch-applied Flashing Systems)
Where potential fire hazards cannot be adequately mitigated, NRCA recommends the direct torching method of membrane flashing application be avoided. Instead, membrane flashings can be applied to appropriate backer flashing configurations using hot- or cold-applied methods of application or indirect torching methods, such as the torch-and-flop method.