Cavity closures at eaves for the residual cavity - 100mm cavity, 90mm PIR

[AndrewBenjamin]

Hi, When the cavity is filled with 90mm PIR there is a 10mm remaining cavity but there are very few details of how this is finished.

In this diagram a closure (circled in red) is shown but I cannot find any products to do this (Fire socks etc are all 65mm or bigger)- any suggestions on what should be used? Thanks

 

[freddiemercurystwin]

The PIR stops and the closer is the whole width of the cavity.

 

[AndrewBenjamin]

The PIR stops and the closer is the whole width of the cavity.

Thanks, does this need to be fire rated, my understanding is cavity closures are not the same as a cavity barrier and not needed in the locations in this diagram: (part B regs) - Manock shows just a flat plate in this version - doesnt this risk bridging the cavity if condensation lands on it from the roof?

 

[freddiemercurystwin]

Don't get too hung up on the terminology, the closer ought to be fire rated, used to be the case that a bit of slate or steel plate would do, they're probably still accepted. The condensation or cavity bridging issue is of no concern, besides the kind of closer mentioned is typically a bit of compressed rockwool wrapped in upvc. The logic behind the regs is to prevent (or slow down) fire spreading into the loft via the cavity.

 

[AndrewBenjamin]

Don't get too hung up on the terminology, the closer ought to be fire rated, used to be the case that a bit of slate or steel plate would do, they're probably still accepted. The condensation or cavity bridging issue is of no concern, besides the kind of closer mentioned is typically a bit of compressed rockwool wrapped in upvc. The logic behind the regs is to prevent (or slow down) fire spreading into the loft via the cavity.

The Kingspan diagram also shows just a plate.
Non of the major DIY type stores stock fire socks, and neither does my local builders merchant so would need to order in. All of them stock standard cavity closers for doors/windows but non of these are specified for the top of the cavity.
I could not see any exapmles of a fire stop or closure being installed in any of the building projects on line, some appear to just have the UPVC sat on the brickwork and open top.
I understand the importance of fire stopping but as fire stopping is not required by the regs for this application but would be happy to fitt the best. However, lack of common availabiltiy suggests that a lot of people just skip adding them. - I will check with my BCO before proceeding either way.