Diagram 30b (Junction of compartment wall with roof) places restrictions on double skinned insulated roof sheeting with a thermoplastic core, asking for the provision of a 300mm band of material of limited-combustibility. Can panels with combustible thermosetting cores be used instead?
In low-rise residential, office or assembly buildings to which Diagram 30b applies, panels with thermosetting cores can be used without any additional protection.
However, fire-stopping must be provided to seal the joint between the compartment wall and the underside of the panel. Any voids above the panel (such as where an additional roof covering is provided) should also be adequately fire-stopped.