The Court of Appeal case of Welwyn Hatfield Borough Council v Secretary of State for Communities and Local Government and another, considered whether a building erected as a hay barn could become a dwelling.

At the outset The Council were mislead as the applicant intended to use the building as a dwelling not withstanding that the application was for a hay barn. He fitted it out internally as a dwelling and moved in. After four years had expired the applicant made an application for a certificate of lawful use to prevent enforcement action for change of use to a single dwelling.

The certificate was refused on the grounds that the barn did not look like a dwelling. A planning inspector reversed this decision. The original refusal was then subsequently reinstated by the High Court on the grounds that the building had never been used other than as a dwelling so there was no change of use. Eventually the Court of appeal allowed an appeal against the High Court decision deciding that because the permitted use was as a hay barn there was a change of use in breach of planning and as the design features were that of a house it was not built in accordance with the planning consent. The Court of Appeal therefore concluded it was too late for the Council to take enforcement action against the construction of the building.