Came across a wrinkle recently that I hope is not common practice. The building code states:
C3.8 Firecells located within 15 m of a
relevant boundary that are not protected by
an automatic fire sprinkler system, and that
contain a fire load greater than 20 TJ or that
have a floor area greater than 5,000 m2
must be designed and constructed so that
at the time that firefighters first apply water
to the fire, the maximum radiation flux at
1.5 m above the floor is no greater than
4.5 kW/m2 and the smoke layer is not less
than 2 m above the floor.
I have come across 2 warehouses, each of about 4000m2, and each within 15m of the same boundary. The warehouses are separated by about 100mm. Each warehouse has its own supporting frame, and external cladding. The side of each warehouse facing the boundary has the relevant fire resistance and protected area, therefore the protection of the neighbour is in compliance with the building code,
The problem is that there is no fire resistance between the warehouses. Any fire occurring in a warehouse will generally spread throughout the warehouse, particularly if it is racked out, as the NZFS risk analysis generally will prohibit their entry in depth. The fire will continue to burn, particularly once the roof starts to collapse. The fire will inevitably attack the inferior sheet metal wall of the warehouse on ire, which will be destroyed, thus exposing the sheet metal wall of the second warehouse. This will also be destroyed, which will cause the area of the building on fire to exceed 5000m2. This directly contravenes C 3.8.
The rationale for this type of construction is based upon the definition of a fire cell, which states that a fire cell needs bounding surfaces ie floor, walls, roof/ceiling. The original definition also included distance as a determining parameter, whereas now this appears to have been lost.
My question is: How are we expected to train a fire to recognise that a sheet metal wall is a fire separation, and that it is not allowed to destroy the wall, or another wall within (say) 20m???