Planning permission is only needed if the work being carried out meets the statutory definition of ‘development’ which is set out in section 55 of the Town and Country Planning Act 1990.
building operations (eg structural alterations, construction, rebuilding, most demolition);
material changes of use of land and buildings;
engineering operations (eg groundworks);
other operations normally undertaken by a person carrying on a business as a builder.
subdivision of a building (including any part it) used as a dwellinghouse for use as 2 or more separate dwelling houses
The categories of work that do not amount to ‘development’ are set out in section 55(2) of the Town and Country Planning Act 1990. These include, but are not limited to the following:
interior alterations (except mezzanine floors which increase the floorspace of retail premises by more than 200 square metres)
building operations which do not materially affect the external appearance of a building. The term ‘materially affect’ has no statutory definition, but is linked to the significance of the change which is made to a building’s external appearance.
a change in the primary use of land or buildings, where the before and after use falls within the same use class.