Purpose Groups and Building Classification

Every building and compartment should be classified according to its use, or intended use, into the most appropriate of those purpose groups given in Table A.1 and – (a) where the use of a building or compartment will vary from time to time, it should be classified as the purpose group to which the more or most onerous provisions in Section 4 apply; (b) where a building or compartment has one or more uses which are not ancillary to the main use of that building or compartment, each portion given over to a separate use should be classified separately; and (c) where the building or compartment has one or more uses which are ancillary to the main use of that building or compartment, each portion given over to an ancillary use should be classified separately when – (i) it is a flat; (ii) in a Purpose Group 4 building or compartment more than 280 m² in floor area – it is storage occupying more than one third of the total floor area of the building or compartment; or (iii) in a building or compartment of any purpose group more than 280 m² in floor area – it is a use [other than in (i) and (ii)] occupying more than one fifth of the total floor area of the building or compartment.