The construction of residential basements beneath existing buildings has become increasingly popular, especially in London, due to land costs and constraints on sideways and upwards development. Concerns have arisen however about the adverse impacts that such developments have on neighbouring property and local amenity.
In November 2016 the Government launched a review of planning law and regulations relating to basement developments, and sought evidence as to whether the adverse impacts of such developments could be further mitigated through the planning process.
The consultation has now closed and the Government's response will be forthcoming. Possible changes could include the removal of permitted development rights for smaller basement developments, so that planning applications for all such developments must be submitted for determination under the relevant local authority's basement policy.
Whether or not Government intervention is actually required is debatable. Two London Councils have now used an Article 4 Direction to remove permitted development rights for basement developments within their boroughs. The High Court has also recently considered the extent to which subterranean development can be carried out relying on the current regime of permitted development rights. In the case of R (Eatherley) v London Borough of Camden & Ireland , the court decided that constructing a basement comprised not only the two aspects of enlargement and alteration of the dwelling, but also the engineering aspect of excavating a space and supporting the house and neighbouring buildings. The court ruled that the first two aspects were allowed as permitted development, but that the engineering aspect was "a separate activity of substance" which required planning permission.
In the light of this ruling, whilst it will be a matter of fact and degree in each case, owners looking to develop their properties will need to be aware that the excavation of a fairly typical single storey basement directly underneath the main part of the original house may not be authorised by permitted development rights alone.