1. Many of the provisions in this document are related to the use of the building. The use
classifications are termed purpose groups and represent different levels of hazard. They can
apply to a whole building, or (where a building is compartmented) to a compartment in the
building and the relevant purpose group should be taken from the main use of the building or
2. Table D1 sets out the purpose groupclassification.
Note: This is only of relevance to this Approved Document.
Ancillary and main uses
3. In some situations there may be more thanone use involved in a building or compartment and in certain circumstances it is appropriate to treat the different use as belonging to a purpose group in its own right. These situations are:
a. where the ancillary use is a flat; or
b. where the building or compartment is more than 280m2 in area and the ancillary use is of an area that is more than a fifth of the total floor area of the building or compartment; or
c. storage in a building or compartment of Purpose Group 4 (shop or commercial), where the storage amounts to more than 1/3rd of the total floor area of the building or compartment and the building or compartment is more than 280m2 in area.
4. Some buildings may have two or more main uses that are not ancillary to one another. For example offices over shops from which they are independent. In such cases, each of the uses should be considered as belonging to a purpose group in its own right.
5.In other cases and particularly in some large buildings, there may be a complex mix of uses. In such cases it is necessary to consider the possible risk that one part of a complex may have on another and special measures to reduce the risk may be necessary.
Table D1 Classification of Purpose Groups. This determines how you decide the basis of compliance in designing your premises.