Right, we’ve had a good look at the meaning of ‘isolated’. Next up, ‘materially larger’.
Paragraph 89 of the NPPF states that planning authorities should regard the construction of new buildings as inappropriate in the green belt. Exceptions include “the replacement of a building, provided the new building is in the same use and not materially larger than the one it replaces”. However, as noted by an inspector dealing with an appeal against the refusal of planning permission for a replacement house in the green belt near Bristol, the NPPF lacks a definition for the term ‘materially larger’ (DCS Number 400-017-236).
In addition to the existing dwelling on the site there was a garage and a number of outbuildings, the inspector recorded. Pointing to its supplementary planning document on green belt dwellings, the council argued that unattached outbuildings should not be counted.
The appellant, on the other hand, drew the inspector’s attention to Tandridge DC v SSCLG & Syrett  where the court held that there is no reason in principle why the objectives of green belt policy cannot be met by the application of the exception to a group of buildings as opposed to a single building. On this basis the inspector did not consider the guidance in the SPD to be consistent with the Framework and therefore afforded it only limited weight. He decided that replacing the existing buildings with the development proposed would have only a minimal spatial and visual impact on the green belt. Although the new dwelling would be larger it would not be materially so, he concluded.
This topic is covered in section 9.631 of DCP Online.