An appeal concerning a sunken seating area at the bottom of the garden of a house in the north London green belt (DCS Number 400-030-752) provides a handy reminder of how it came about that a detached outbuilding can be regarded as an extension for planning purposes.
The inspector agreed with the appellant that the covered seating area and its surrounding structure would undoubtedly be incidental to the enjoyment of the dwelling but judged that that did not necessarily render it an extension for green belt purposes. The appellant drew the inspector’s attention to the Sevenoaks District Council v Secretary of State for the Environment and Dawe  judgment, where it was found that an extension to a dwelling need not necessarily be physically attached to the dwelling and that it could include ‘normal domestic adjuncts’. The inspector considered that, whilst normal domestic adjuncts were not defined, they should have a close physical relationship with the main house such that visually they would appear grouped with the main house. In the case before him, however, the covered seating area would be at the bottom of the garden and separated from the main house by a watercourse as well as an extensive garden area. Accordingly, it would not constitute a ‘normal domestic adjunct’ and therefore was not an extension or alteration of a building as per paragraph 145 (c) of the NPPF. It would therefore constitute inappropriate development in the green belt.
Further appeal cases in which Dawe has been cited can be found at section 4.2513 of DCP Online, which deals with appropriateness in the green belt.