An inspector dealing with an appeal against the refusal of a lawful development certificate for a detached swimming pool and store at a house in west Yorkshire (DCS Number 400-015-315) has helpfully set out the case law on the definition of curtilage, which readers might find it useful to cut out and keep.
There is no authoritative or precise definition of the term ‘curtilage’, the inspector recorded. However, to fall within the curtilage of a building, land should serve the purpose of the building in some reasonably necessary or useful manner, he explained. This was established in Sinclair-Lockhart’s Trustees v Central Land Board . In Methuen-Campbell v Walters  it was found that for land to fall within the curtilage of a building or other land there must be an intimate association. In the Court of Appeal case, Dyer v Dorset CC , it was held that curtilage is a small area forming part and parcel with the house or building which it contained or to which it was attached. In that context, the judge commented that the kind of ground most usually attached to a dwelling house is a garden.
These authorities, including Methuen-Campbell, were reviewed in McAlpine v SSE  which indicated, amongst other things, that curtilage is a small area about a building, that the curtilage land must be intimately associated with the building, and that the size of the area of ground is a matter of fact and degree. McAlpine also reiterated the finding in Sinclair-Lockhart that curtilage land should serve the purpose of the building within it in some reasonably necessary or useful manner.
The appellant in (DCS Number 400-015-315) also referred to the High Court case of Sumption v London Borough of Greenwich and Rokos , the inspector noted. He explained, however, that Sumption does not undo the precedent set by the Court of Appeal, and so does not establish, as a matter of law, that the curtilage of a dwellinghouse can be expanded simply by annexing adjoining land, which itself is being used for garden purposes.
Applying these rulings to the case before him, the inspector reasoned that smallness (Dyer) of the land in question was a relative factor; a matter of fact and degree. In his view the appeal site was not disproportionately large in width, length or area given the large size of the detached dwelling house and its original plot. As a matter of fact and degree, he considered it to be small relative to the size of the dwelling. Moreover, it was not so large that the furthest extent of it could be said to be unable to have an intimate association (Methuen-Campbell) with the house. Its use as a cultivated garden with play equipment, still in situ at the time of his visit, indicated to him that it did have an intimate association with the use of the house, and as a domestic garden it served the purpose of the dwelling house in a reasonably useful manner (Sinclair-Lockhart). This appeared to him to have been the case for a number of years prior to the date of the application.
The inspector concluded that the appeal site formed part of the curtilage of the dwelling. Consequently, an LDC was granted for the proposed outbuildings as they would be permitted development within Schedule 2, Part 1, Class E of the GPDO.
The following DCP chapter is relevant: 4.3444 and 12.912