11.—(1) In this Order, subject to paragraphs (2) to (4), “development” means the carrying out of building, engineering, mining or other operations in, on, over or under land, or the making of any material change in the use of any buildings or other land.
(2) The following operations or uses of land shall not be taken for the purposes of this Order to involve development of the land—
(a)the carrying out of works for the maintenance, improvement or other alteration of any building, being works which affect only the interior of the building or which do not materially affect the external appearance of the building;
(b)the carrying out by a district council or statutory undertaker of any works for the purpose of inspecting, repairing or renewing any mains, pipes, cables or other apparatus, including the breaking open of any street or other land for that purpose;
(c)the use of any buildings or other land within the curtilage of a dwelling-house for any purpose incidental to the enjoyment of the dwelling-house as such;
(d)the use of any land for the purposes of agriculture or forestry and the use for any of those purposes of any building occupied together with land so used;
(e)in the case of buildings or other land which are used for a purpose of any class specified in an order made by the Department for the purpose of this Article, the use of the buildings or other land or, subject to the provisions of the order, of any part thereof for any other purpose of the same class.
(3) For the purposes of this Article—
(a)the use as two or more separate dwelling-houses of any building previously used as a single dwelling-house involves a material change in the use of the building and of each part thereof which is so used;
(b)the deposit of refuse or waste material on land involves a material change in the use thereof, notwithstanding that the land is comprised in a site already used for that purpose, if either the superficial area of the deposit is thereby extended, or the height of the deposit is thereby extended and exceeds the level of the land adjoining the site.
(4) Without prejudice to any regulations made under this Order relating to the control of advertisements, a use for the display of advertisements of any external part of a building which is not normally used for that purpose shall be treated for the purposes of this Article as involving a material change in the use of that part of the building.
12. Subject to this Order, planning permission is required for the carrying out of any development of land.