Fire Resistant Cavity/Smoke Barrier

The purpose of a cavity and smoke barriers is to prevent the spread of smoke and flame from penetrating and/or moving within a concealed space in a fire compartment. Documents supporting the regulations provide guidance on where such barriers should be located within hidden voids in a building and they usually give examples of deemed-to-satisfy barriers for voids in or above stud walls or partitions.

If a barrier in a concealed space coincides with a compartment wall or floor it will normally be required to provide the same fire performance as the wall or floor. If the barrier is located between such compartment walls or floors however, the barrier is defined as a “cavity barrier” and will normally only be required to provide 30 minute integrity and 15 minute insulation (depending on local building regulations).

A parapet is a low standing wall above a roof, on top of either an external wall or a fire separating wall. A parapet wall is supposed to prevent fire venting through the roof on one property and crossing over the separating wall down into any adjacent property.

A spandrel panel is used generally as part of curtain walling systems. The spandrel panel generally protects vertically up from the top of a floor slab, or down from the underside of a floor slab. Spandrel panels are supposed to deflect fire and prevent spread of flames via the ends of floor slabs. A spandrel wall is designed to form a separator at any part of a window or an opening in an external wall above another opening in the storey below. The vertical construction projects no further than 450mm outside the lower opening.

Parapet and spandrel walls should normally be approved in accordance with the criteria of BS 476: Part 22: 1987, which is required to satisfy a minimum fire resistance of 60/60/60 (for exceptions please check with local building regulations guidance documents or, if relevant, insurance codes).