England and Wales

Provision for structural fire resistance of buildings is embodied in Part B of Schedule 1 of the Building Regulations 2000 as follows:

“The building shall be designed and constructed so that, in the event of fire, its stability will be maintained for a reasonable period”. 

Approved Document B, Figure 2, interprets the requirements of the Building Regulations and states that the stability criterion will be satisfied if “the load bearing elements of the structure of the building are capable of withstanding the effects of fire for an appropriate period without loss of stability”.

The Approved Document contains detailed provisions for the maintenance of structural stability in fire. These are intended to provide guidance for some of the most common building situations.

Guidance on ‘appropriate periods’ for different building occupancies is given in Table A2 of the Approved Document (summarised in Table 1, above). However, these fire resistance periods are not mandatory. The Approved Document states that:

“There is no obligation to adopt any particular solution contained in an Approved Document if you prefer to meet the relevant requirement in some other way”.

The Approved Document goes on to suggest ‘other means’ to demonstrate compliance by stating that:

“Fire safety engineering can provide an alternative approach to fire safety. It may be the only practical way to achieve a satisfactory standard of fire safety in some large and complex buildings and in buildings containing different uses”.

The most important aspects of the Approved Document concerning structural fire resistance are:

• Fire resistance periods are based on building height and occupancy.
• The height of a building, for the purpose of determining fire resistance, is measured from the ground to the floor of its uppermost storey. The top storey is not included (Figure 3, below). 

Height of top storey

• A reduction of 30 minutes in the required fire resistance may be applied to most types of non-domestic occupancies less than 30 metres in height when an approved sprinkler* system is installed.
• The maximum fire resistance period for superstructures and basements is 120 minutes.
• Compartment sizes can be doubled in many instances where sprinklers* are installed.
• All non-residential buildings over 30 metres in height must now be equipped with sprinklers*.
• Structural elements of open deck car parks require only 15 minutes fire resistance. The majority of Universal steel sections will survive a 15 minute standard fire test and thus most steel framed open deck car parks do not require structural fire protection. Full details are given in the Corus publication, Steel Framed Car Parks.

* Sprinklers mean an automatic sprinkler system meeting the relevant recommendations of BS EN 12845: 2004, with additional requirements for life safety.