New legislation laid in Parliament yesterday includes the introduction of the Class AA permitted development right which provides for the ‘enlargement of a dwellinghouse by construction of additional storeys’, to take effect from 31st August 2020. With prior approval from the Local Planning Authority, homeowners will soon be able to add immediately above the topmost storey: a) up to two additional storeys on pre-existing dwellinghouses of two or more storeys; and b) one additional storey on existing dwellinghouses comprising one storey. Existing accommodation in the roof space, including a loft extension, is not deemed a storey for the purpose of this right. The legislation, applying equally to detached, semi-detached and terraced houses, stipulates that the additional storeys are to be of a similar appearance in terms of exterior materials and that the development must not feature a window in any wall or roof slope forming a side elevation. Further, the roof pitch of the main part of the dwellinghouse post construction must be equal to the roof pitch of the existing dwellinghouse.
The new PD right is subject to several limitations and conditions, prohibited namely to: dwellings created via changes of use; dwellinghouses situated within a National Park, AONB, Conservation Area or SSSI; and, dwellinghouses constructed before 1st July 1948 or after 28th October 2018. Indeed, dwellinghouses already enlarged by the construction of one or more storeys are not applicable. Various constraints relate to the height of the proposed roof and the floor to ceiling height of any additional storey. Within the prior approval application, due consideration must be attributed, principally, to amenity including overlooking, privacy and loss of light and the external appearance of both the principal elevation and any side elevations that front a highway.
The legislation can be assessed here: