Lift a ceiling tile and look along the void.
If you can see right down the corridor and into the next room, there is no barrier in it. Smoke and fire can run along that space above everyone's head.
What a cavity barrier does
A cavity barrier closes a hidden space. It might be a ceiling void, a roof space, a gap behind cladding or the cavity inside a stud wall.
It is different from fire stopping, which seals a hole that something passes through. A barrier closes the cavity itself.
Where they go
Along the line of a fire wall, so the void above is cut off at the same place the wall is.
Around the top of a partition that stops at a suspended ceiling.
At the edges of openings, round a window or a vent in a cavity wall.
At the junction between a wall and the underside of a roof.
Where we find them missing most is above corridor ceilings and in the roof space of older buildings, where several trades have crossed a line without checking.
What we find
Barriers that were never fitted.
Barriers that were cut to get a cable through and never repaired.
Mineral wool stuffed in loosely. It has to be fitted tight and held in place.
Barriers that stop an inch short of the slab, which leaves a slot for smoke.
The wrong product. A board or a sleeve that is meant for something else.
How we fix it
In a stud void the barrier is usually board or mineral wool held in a frame. In a ceiling void it is a barrier cut to the depth of the void and fixed tight to the wall and the slab. At the edges we use intumescent seals and mastic.
The product has to match the void and the way it is fixed. Our BM TRADA / FIRAS-certificated contractors follow the manufacturer's fixing detail.
Each barrier is photographed in position with a label, so your assessor can tick it off.
Questions we get asked
Is a cavity barrier the same as a fire stop?
No, though they work together. A fire stop seals a hole. A cavity barrier closes a void.
How do I know if mine are missing?
Open a few access points along a corridor. A survey does it properly and records what is found.
Send it over with the postcode. We will tell you what the work involves and roughly what it costs.
Get a price