What are use classes?
The Town and Country Planning (Use Classes) Order 1987 (as amended) (UCO) sets out various categories of use referred to as “use classes”, which relate to the use of land and buildings. Examples of these use classes are: A1 (shops), B1(business), and C3 (dwellinghouses).
You will usually need planning permission to change from one use class to another, although there are exceptions where the legislation does allow some changes between uses. This is called "permitted development" and the relevant legislation is The Town and Country Planning (General Permitted Development) Order 2015 (GPDO) (as amended). The Change of Use – Use Classes section of the Planning Portal provides further information about what is normally covered by the Use Classes, including the fact that certain uses do not fall in any category and are considered to be 'sui generis' - which means unique.
It should also be noted that sometimes what are known as Article 4 Directions may take away rights to carry out development which would otherwise be allowed by the GPDO – your local planning authority should be able to advise if this applies to your area. Also conditions on a planning permission might take away rights to change uses under the UCO or the GPDO or to build extensions, etc under the GPDO – for instance, large stores on retail parks sometimes have conditions on their planning permissions preventing the sale of food, so they do not adversely affect sales from nearby shopping centres. In addition, if a premises has changed use under a "prior notification" provision of the GPDO, then there may be further restrictions on subsequent changes of use.
Sometimes it is difficult to establish the lawful use of a premises, particularly if it has changed over time and/or does not operate in a consistent way. For this reason, it is important for your local planning authority (LPA) to advise, based on the particular circumstances of each site, which use class a particular use falls into and what use is considered lawful. The Lawful Development Certificate process can greatly help in this regard.