SFPE Discussions

SH v SM Risk Groups

Single storey building with a shop/dairy/takeaway to front and living space at the rear - can this be treated as risk group SH? Or is it SM?

Hi Tim,
Where part of a building is another risk group the building/firecell cannot be SH. 1.1.2 of C/AS1 refers.


Thanks Gillian. In the now superceded C/AS2 fro SM risk group clause 2.2.10 allowed SH to be used but I see that clause has been deleted in the new C/AS2. Interestingly so has clause 2.2.11.I will proceed on the basis of SM. Cheers.

Hi Tim
I’m not sure which 2.2.11 you are referring to but I would suggest that the driving clause will be (in new C/AS2) 1.2.1(b) then steps 2 and 3.

Now I am confused. Maybe i did not ask the question correctly. The old C/AS2 (10 April 2012) had clause 2.2.10 that allowed SM units (such as the one I have) to be designed as SH. That clause is not included in the new C/AS2 (27 June 2019). So I am guessing that a SM unit is always an SM unit.

I noted (and this is unrelated to the original question) that clause 2.2.11 in the old C/AS2 (upper floor with SM always has to have smoke detection in the floor below) has gone from the new C/AS2 which I thought was strange.

Tim, The old C/AS2 referred to household units one above another in 2.2.10, so that wouldn’t apply to your dairy example.
2.2.11 (lower floors / risk groups require type 4 or 5) is still covered (although not as clearly worded in -
> Same risk group on different floors
*> 2.2.7 Where firecells containing the same *
*> risk group occur at different levels in the *
*> same building, the fire safety systems *
*> for the firecell having the most onerous *
*> requirements shall be applied to all firecells *
> of that risk group.