Elements of structure in buildings

Approved document B, Fire Safety, Volume 2, Buildings other than dwellinghouses, paragraph B3.iii defines ‘elements of structure’ as:

…the term applied to the main structural loadbearing elements, such as structural frames, floors and loadbearing walls. Compartment walls are treated as elements of structure although they are not necessarily loadbearing. Roofs, unless they serve the function of a floor, are not treated as elements of structure.

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, are not regarded as loadbearing for the purposes of B3.ii(a), although they may need fire resistance to satisfy requirement B4 (see Sections 8 to 9).

Loadbearing elements may or may not have a fire-separating function. Similarly, fire-separating elements may or may not be loadbearing.

Notes:

• B3.ii(a) refers to the resistance to collapse, i.e. the ability to maintain loadbearing capacity (which applies to loadbearing elements only).
• B4 refers to 'external fire spread' and requires that:

1. The external walls of the building shall adequately resist the spread of fire over the walls and from one building to another, having regard to the height, use and position of the building.
2. The roof of the building shall adequately resist the spread of fire over the roof and from one building to another, having regard to the use and position of the building.

• Section 8 relates to compartmentation.
• Section 9 relates to concealed spaces (cavities).

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