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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

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.

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