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).