Section 7: Loadbearing elements of structures

Fire resistance standard

7.1 Elements such as structural frames, beams, columns, loadbearing walls (internal and external), floor structures and gallery structures should have, as a minimum, the fire resistance given in Appendix B, Table B3.

7.2 Appendix B includes guidance on all of the following.

a. Provisions to ensure that where one element of structure supports or stabilises another element of structure, the supporting element has no less fire resistance than the other element (see Table B4).

b. Measures so that elements common to more than one building or compartment are constructed to the standard of the more onerous of the relevant provisions.

c. Special provisions about fire resistance of elements of structure in single storey buildings.

d. Concessions in respect of fire resistance of elements of structure in basements where one or more sides of the basement are open at ground level.

Exclusions from the provisions for elements of structure

7.3 The following are excluded from the definition of ‘element of structure’.

a. A structure that supports only a roof, unless either of the following applies.

i. The roof performs the function of a floor, such as for parking vehicles, or as a means of escape.

ii. The structure is essential for the stability of an external wall that needs to be fire resisting (e.g. to achieve compartmentation or for the purposes of preventing fire spread between buildings).

b. The lowest floor of the building.

c. A platform floor.

d. A loading gallery, fly gallery, stage grid, lighting bridge or any gallery provided for similar purposes or for maintenance and repair.

e. External walls, such as curtain walls or other forms of cladding, which transmit only self weight and wind loads and do not transmit floor load.

NOTE: In some cases, structural members within a roof may be essential for the structural stability system of the building. In these cases, the structural members in the roof do not just support a roof and must demonstrate the relevant fire resistance for the building as required by paragraph 7.2a above.

Additional guidance

7.4 If a loadbearing wall is any of the following, guidance in other sections may also apply.

a. A compartment wall (including a wall common to two buildings): Section 8.

b. Enclosing a place of special fire hazard: Section 8, paragraph 8.7.

c. Protecting a means of escape: Sections 2 to 5.

d. An external wall: Sections 12 and 13.

e. Enclosing a firefighting shaft: Section 17.

7.5 If a floor is also a compartment floor, see Section 8.

Raised storage areas

7.6 The normal provisions for fire resistance may be too onerous to apply to raised, free-standing floors (sometimes supported by racking) in single storey buildings used for industrial and storage purposes. The introduction of raised storage areas can alter the effective number of storeys in the building (see the definition of ‘storey’ in Appendix A).

7.7 A structure that does not have the minimum fire resistance specified in Appendix B, Table B4, is acceptable if it satisfies all of the following conditions.

a. The structure meets both of the following conditions.

i. It has only one tier.

ii. It is used for storage purposes only.

b. The people likely to be on the floor at any one time are both of the following.

i. Few in number.

ii. Not members of the public.

c. The floor is open above and below to the room or space in which it is situated.

d. The means of escape from the floor is in accordance with Sections 2 to 5.

e. The floor meets both of the following conditions.

i. It is not more than 10m in width or length.

ii. It is a maximum of half the floor area of the space in which it is situated. The limitations in (e) may be adjusted if any of the following apply.

f. If the lower level has an automatic fire detection and alarm system meeting the recommendations of BS 5839-1, then the floor size may be increased to not more than 20m in either width or length.

g. If agreed with the building control body and the fire and rescue service, then it may be possible to vary this dimension and area. However, the safety of firefighters and the distance they may need to travel over or under the floor must be considered.

h. If the building is fitted throughout with an automatic sprinkler system complying with Appendix E, then no limits are set for the size of the floor.