The project would comprise a ground floor and five upper floors, the uppermost floor being 18.5m above ground level. A fire safety strategy had been prepared by Cundall Johnston and Partners in-house fire consultant. Their work proposed the following: design to be developed using BS 9999: 2008, with an A2 risk profile; no sprinklers would be installed; L2 AFD system proposed throughout; occupancy levels based on floorspace factor of 6 m2 per person, and travel distances and escape routes in accordance with recommendations of BS 9999; three lobby protected stairs would be incorporated with widths not less than 1100 mm; simultaneous evacuation of the building; each floor to be designed and constructed to the same level of protection as a fire compartment floor; atrium to be provided with automatic opening vents for a ‘temperature control’ system; building facades do not require fire resistance; access for fire crews will be by way of a dedicated firefighting shaft in the central core with additional access in well protected escape stairs, if required; car park in ground and first floors to be provided with natural smoke vents.
I was appointed by the building control officer (BCO) to comment on and give a second opinion on several features. A meeting was held with the design team and when the issue of building separation arose it was agreed to accept a pragmatic approach to building separation:
a) it would be assumed that a radiator representing 1½ storeys on fire should be adopted in the calculation of radiation, there being no sprinklers in the building – I suggested this to allow for the lesser fire severity associated with a growing/spreading fire scenario on the second floor involved in fire after flashover on the floor below.
b) a calculation was needed estimating the amount of ventilation required to the atrium in order to dilute the smoke plume to an extent whereby the temperature of the smoke will be insufficient to result in the failure of toughened glazing on the storey two floors above the floor of fire origin.
The BCO and I also felt that at least one fire main should be included in the fire safety package – the floor area was greater than the 980m2 used as a criterion as to whether or not a fire main is needed in a building over 18m high
I also pointed out that a) the 10% smoke ventilation criterion is ventilation for smoke clearance after a fire to aid fire fighting and was needed if windows are not openable (BS 9999 clause B.10.1 refers) and this, of course, plays no part in the life safety of occupants, and b) the design team might decide that the atrium should be glazed in fire resisting glass and if this is so, there should be proof (an assessment) that any large unframed panes of glass will stay in place for the duration of the fire.
I also checked and commented on the fire engineer’s calculations for building separation distance for the condition of 5m to notional site boundary.
Client: Building Control Approval Ltd
