Planning rules relating to home extensions are complex but a householder’s victory in a High Court test case is expected to make it significantly easier for some people to enlarge their homes without the need for planning permission.

The man had already built a two-storey extension to his home pursuant to a planning consent granted in 2000. However, he wished to construct a further single-storey extension and applied to the local authority for prior approval. He argued that the extension would be permitted development, not requiring permission.

In refusing to grant approval, the council disagreed and its decision was subsequently upheld by a government planning inspector. The man’s challenge to the latter decision hinged on the meaning of the phrase ‘the enlarged part of the dwelling house’ in the Town and Country Planning (General Permitted Development) (England) Order 2015.

The Order automatically grants planning consent for many modest home extensions, but does not permit developments that are greater than a certain area or height or where the enlarged part would be more than one storey. The inspector held that the enlarged part was not merely the extension proposed but included the earlier extension. The consequence, he found, was that the proposal was not permitted development as the pre-existing extension had more than one storey.

In upholding the man’s challenge to that decision, the Court held that the inspector had erred in law. On a true interpretation of the Order, the enlarged part of the dwelling included only the proposed new extension. The earlier extension should therefore have been left out of account. It is considered that the Court’s decision may require amendment of government guidance on householder permitted development rights.