Change of Use

Section 55 of the Town and Country Planning Act 1990 defines 'development' as, among other things, 'the making of any material change in the use of any buildings or other land'. The Act deems certain changes to automatically be a material change — for example, converting a building previously used as a single dwellinghouse into two or more separate dwellinghouses, or using an external part of a building not normally used for advertising to display advertisements — while other operations, such as works affecting only the interior of a building or works that do not materially affect its external appearance, are expressly excluded from counting as development at all.

Not every change of use triggers a fresh requirement for planning permission. Section 55(2)(f) allows the Secretary of State to specify, by order, classes of use such that moving from one use to another within the same class is not treated as development — the mechanism underpinning the Use Classes Order. Where a change of use falls outside any such permitted class, or is expressly treated by the Act as a material change (such as splitting a single dwellinghouse into flats), it is development and planning permission must be sought.