3 Permitted Development

12.103 The development permitted includes the following.

(a) The extension or alteration of an agricultural building

12.104 Class B does not authorise the erection of buildings (Cf Class A above).

•Notification requirements: The notification requirements (Class A2(2) above) apply in the case of Class B development only to the extension or alteration of a building situated on Art 2(4) land ie within or adjacent to a National Park. In this event the local planning authority can subject the siting, design or appearance of the building as extended or altered to their prior approval (Class B.5(2)).

•Extension and/or alteration of buildings is not permitted if the external appearance of the premises would be materially affected (Class B. 1(b)) or if it would involve carrying out work to a building used (or to be used) for the storage of slurry or sewage sludge, or for livestock accommodation if the building is within 400 metres of a protected building (eg a dwelling). Where building work has been carried out under Class B within 400 metres of a protected building, then the building so altered or extended can only be used for housing livestock in the temporary and emergency contingencies envisaged by Class D.1(3).

•Development is not permitted if the height of any building would be increased (by whatever amount) or if the cubic content of the original building would be increased by more than 10 per cent. Neither is extension permitted where any part of the building would be more than 30 metres from the original building (Class B.2(a)-(c)).

•The provision, alteration or extension of a dwelling is not permitted (Class B.2(e)).

•No development is permitted within 5 metres of any boundary of the agricultural unit (Class B.2(f)). This restriction does not apply under Class A (above).

•Development is not permitted if the ground area of any building extended under Class B would exceed 465 square metres (Class B.2(g)). By virtue of Class D.1(2) the ground area of any building provided during the previous two years, and any part of which would be within 90 metres of the extended building, must be aggregated when calculating the size limit. Where two or more buildings within the same curtilage are used for the same undertaking they are to be treated as a single original building when aggregating floor space for this purpose (Class D.1(5)(b)), and also for the purposes of other measurements under Class B (eg calculating the cubic content of the original buildings prior to extension).

(b) Installation of plant and machinery

12.105 Class B.3 subjects this right to a height restriction of 3 metres within 3 kilometres of the perimeter of an aerodrome, and 12 metres elsewhere. The height of any plant and machinery being replaced must not exceed that of the original, and the floor area to be covered must not exceed 465 square metres. Aggregation (see Class D.1(2)) applies for this purpose, as for extensions and additions to buildings (above).

(c) Deposit of waste

12.106 This is permitted by Class B(f). But note that waste can only be brought onto the land with the Class B permission if it is for the purpose of permitted building works or the creation of a private way or hard surface. The waste material must, moreover, be incorporated into the intended works forthwith. The height of the surface of the land must not be materially increased (Class B.5(3)).