What is the difference between a cavity barrier and a cavity closer?

Firstly, the term cavity barrier is mentioned 85 times and the term cavity closer is not mentioned once within Part B Building Regulation 2019 – and there is good reason for this.

So, what is a cavity? “A space enclosed by elements of a building (including a suspended ceiling) or contained within an element, but that is not a room, cupboard, circulation space, protected shaft, or space within a flue, chute, duct, pipe or conduit.” (Part B, 2019)

Secondly, what then is a cavity barrier? A cavity barrier is a construction within a cavity, other than a smoke curtain, to perform either of the following functions.

• Close a cavity to stop smoke or flame entering.
• Restrict the movement of smoke or flame within a cavity

A cavity closer, if fire rated, can act as a cavity barrier. However, a cavity closer has a number of other functions, which a cavity barrier does not need to activate.

• Minimise heat loss out of a building
• Prevent water ingress and cold penetration into a building
• + create a fire barrier if a fire rated cavity closer is used

Therefore, a cavity closer is also a cavity barrier if it is fire tested. However, a cavity barrier will not all ways be a cavity closer.

Cavity closer are also only used around reveals, such as window and door reveals. Whereas a cavity barrier can be used any where within a cavity, as required and see out in Part B Building Regulation 2019.

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