A. The extension or alteration of an industrial building or a warehouse.
A.1 Development is not permitted by Class A if—
(a)the building as extended or altered is to be used for purposes other than those of the undertaking concerned;
(b)the building is to be used for a purpose other than the carrying out of an industrial process, or, in the case of a warehouse, other than storage or distribution;
(c)the height of the building as extended or altered would exceed the height of the original building;
(d)the cubic content of the original building would be exceeded by more than—
(i)10%, in respect of development on any article 1(5) land, or
(ii)25%, in any other case;
(e)the floorspace of the original building would be exceeded by more than—
(i)500 square metres in respect of development on any article 1(5) land, or
(ii)1,000 square metres in any other case;
(f)the external appearance of the premises of the undertaking concerned would be materially affected;
(g)any part of the development would be carried out within 5 metres of any boundary of the curtilage of the premises; or
(h)the development would lead to a reduction in the space available for the parking or turning of vehicles.
A.2.—(1) For the purposes of Class A—
(a)the erection of any additional building within the curtilage of another building (whether by virtue of this class 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.