Fire resistance of buildings

Approved Document B Fire Safety, Volume 2, Buildings other than dwellinghouses (2019 edition), defines fire resistance as:

'The ability of a component or a building to satisfy, for a stated period of time, some or all of the appropriate criteria given in the relevant standard.'

Fire resistance is a measure of one or more of the following:

Resistance to collapse (loadbearing capacity), which applies to loadbearing elements only, denoted R in the European classification of the resistance to fire performance.
Resistance to fire penetration (integrity), denoted E in the European classification of the resistance to fire performance.
Resistance to the transfer of excessive heat (insulation), denoted I in the European classification of the resistance to fire performance.

Fire resistance is measured in minutes. This relates to time elapsed in a standard test and should not be confused with real time.

Performance in terms of the fire resistance to be achieved by elements of structure, doors and other forms of construction is classified in accordance with BS EN 13501.

Other information about fire resistance in the approved document includes:

Table B3 gives the specific requirements for each element of structure.
Table B4 sets out the minimum periods of fire resistance for elements of structure.
Table B5 sets out limitations on the use of uninsulated fire resisting glazed elements.