Flat roof over compartment line

[Dunbar]

I am looking at a care home with a flat roof it has 4 compartments on the top floor but having popped a tile or two the block work stops under the roof joists and OSB decking with clear gaps under the timber into the next compartment. i.e. if the roof caught fire it would pass over the compartment line. My understanding is that all compartment lines should either be taken through the roof or go up to the deck with 1.5m of limited combustible material either side. This is a new build but has been approved and signed off as fine. AD B seems to back my thinking up in institutional buildings. Page 76

It was described as a sacrificial roof to me but in progressive horizontal evacuation that for me isn't practical i.e. having fire spread over the heads of the compartment you have just moved in to. it could mean you have to move all compartments vertically very quickly.

Can anyone point me to the direction of the appropriate text preferably with a drawing to back it up.

 

[kurnal]

Your first paragraph is correct.

Your second paragraph refers to a sacrificial roof, this is not a phrase that appears in any building design codes that I have read. In practical terms though it's a no brainer to fill in gaps at the head of the wall but doing anything meaningful with the roof decking is probably not practicable. Most fires will occur in rooms, fires in roof spaces are fairly rare and the risk can be controlled by good housekeeping and maintenance in the roof space. You could also install some intermediate cavity barriers as a compensatory feature

[wee brian]

Agreed, sounds like B.S. to me.

Probs the builder forgot and the BCO missed it. (or worse)