cavity closure at top of wall

[nottsrob184]

Hi all.
Just finished building one side wall of a single storey extension, (other side still to do. Question is this....do i have to close the cavity of the inner and outer wall at the top? and if so what with.
I was planning of leaving it open.
Thanks foe any advise.

 

[freddiemercurystwin]

If you have partial fill cavity insulation then technically you're supposed to, you can buy manufactured cavity closers which basically consist of some fire resistant insulation wrapped in a bit of dpm although normally a bit of old slate or similar will do.

The Regs suggest:

* steel at least 0.5mm thick
* timber at least 38mm thick
* polythene sleeved mineral wool, or mineral wool slab under compression
* calcium silicate, cement or gypsum based boards at least 12mm thick

Unless you have full fill cavity insulation in which case you don't need to.

Whichever you have though your cavity insulation should meet up with your roof insulation so as to form a continuous 'insulation bubble'.