| Class A | ||
| Permitted development | A. | The erection or construction and the maintenance, improvement or other alteration by or on behalf of the Crown of— (a) any small ancillary building, works or equipment on Crown land and required for operational purposes; or (b) lamp standards, information kiosks, public shelters and seats, telephone boxes, fire alarms, electric car charging points, drinking fountains, refuse bins or baskets, barriers for the control of people and vehicles, and similar structures or works required in connection with the operational purposes of the Crown. |
| Interpretation of Class A | A.1 | The reference in Class A to any small ancillary building, works or equipment is a reference to any ancillary building, works or equipment not exceeding 4 metres in height or 200 cubic metres in capacity. |
| Class B | ||
| Permitted development | B. | The extension or alteration by or on behalf of the Crown of an operational Crown building. |
| Development not permitted | B.1 | Development is not permitted by Class B if— (a) the building as extended or altered is to be used for purposes other than those of— (i) the Crown; or (ii) the provision of employee facilities; (b) the height of the building as extended or altered would exceed the height of the original building; (c) the cubic content of the original building would be exceeded by more than— (i) 10% in respect of development in a conservation area, an area of outstanding natural beauty or a National Park; or (ii) 25% in any other case; (d) the floor space of the original building would be exceeded by more than— (i) 500 square metres in respect of development in a conservation area, an area of outstanding natural beauty or a National Park; or (ii) 1000 square metres in any other case; (e) the external appearance of the original building would be materially affected; (f) any part of the development would be carried out within 5 metres of any boundary of the curtilage of the original building; (g) any part of the development would be carried out within any boundary of the curtilage of the original building which adjoins the curtilage of any dwellinghouse or flat; or (h) the development would lead to a reduction in the space available for the parking or turning of vehicles. |
| Interpretation of Class B | B.2 | For the purposes of Class B— (a) the erection of any additional building within the curtilage of another building (whether by virtue of Class B or otherwise) and used in connection with it is to be treated as the extension of that building, and the additional building is not to be treated as an original building; (b) where two or more original buildings are within the same curtilage and are used for the same undertaking, they are to be treated as a single original building in making any measurement; (c) “employee facilities” means social, care or recreational facilities provided for employees of the Crown, including crèche facilities provided for the children of such employees. |
| Class C | ||
| Permitted development | C. | Development carried out on operational Crown land for operational purposes consisting of— (a) the installation of additional or replacement plant or machinery; (b) the provision, rearrangement or replacement of a sewer, main, pipe, cable or other apparatus; or (c) the provision, rearrangement or replacement of a private way, private railway, siding or conveyor. |
| Development not permitted | C.1 | Development described in Class C(a) is not permitted if— (a) it would materially affect the external appearance of the premises of the undertaking concerned; or (b) any plant or machinery would exceed a height of 15 metres above ground level or the height of anything replaced, whichever is the greater. |
| Interpretation of Class C | C.2 | In Class C, “Crown land” does not include land in or adjacent to and occupied together with a mine. |
| Class D | ||
| Permitted development | D. | The creation by or on behalf of the Crown of a hard surface within the curtilage of an operational Crown building. |