Under section 55(2)(a) of the Town and Country Planning Act 1990 (TCPA 1990), planning permission is not required for the carrying out for the maintenance, improvement or other alteration of any building of works which affect only the interior of the building, or do not materially affect the external appearance of the building. This include mezzanine floors, subject to exceptions for retail premises. TCPA 1990, s 55(2)(f) states that a change in the use of land or buildings, where the previous and new use falls within the same use class,