I thought an L2 system was required in the common parts - ie. a heat detector inside the front door of each flat connected to the common system as well as sounders within bedrooms etc?
How do you get away with L4??
The consultant/contractor and everyone else involved should be questioned....
Notwithstanding the recent fire in Camberwell, there is not normally any requirement for common areas in blocks of self contained flats. The one hour enclosures around each flat are justification for the 'defend in place' (sit tight, stay put, call it what you will) fire strategies that are applied. The only alarm requirements are normally for part 6 systems within flats - they are there to get people to their front doors - the assumption being that from that point on they are safe due to the compartmentation.
There are a range of premises where there may be a need for common area coverage, maybe halls of residence, sheltered flats, etc, but not normally 19 storey blocks of self contained flats.
Now, returning to Camberwell, there are bound to be widespread questions about the reliability of this compartmentation and about the effectiveness of the 'defend in place' policy but we can't speculate in that direction until more is revealed about the particular circumstances of that case.
I feel that it is unlikely that there will be any change to the pragmatic 'defend in place' policy. We're more likely to see significant issues raised regarding compartmentation.
On that issue, if fire did spread via external means then this is starting to become a recurrent problem and there may be a need to reconsider the traditional stance of assuming that compartmentation will not be breached by external means along a horizontal wall.
Stu