A Slough garden dwelling could not be saved on appeal by switching to an incidental gym and store, although another route remains open.
The fallback was outside the ground (a) deemed application, although the Inspector gave extra time for an alternative scheme to be put to the council.
The notice attacked both the building and its use
The appeal concerned 9 Elmshott Lane, Slough. The enforcement notice, issued on 6th November 2025, alleged “the unauthorised erection of a self-contained building and its use as a self-contained dwelling”.
That wording was crucial. The notice did not merely object to someone living in an otherwise lawful outbuilding. It alleged that the building itself was unauthorised operational development as well as objecting to its use as a separate dwelling.
The notice required the dwelling use to stop, the kitchen, shower room and associated plumbing to be removed, and ultimately the building to be demolished and cleared from the land.
Building control did not settle the planning position
The appellant argued that the structure had been built as a Class E outbuilding incidental to the main house. He relied on plans from October 2022 and a building control certificate dated 23rd May 2024 that described the work as an outbuilding and said it did not concern a dwelling.
But Slough’s later planning evidence told a different story. Council photographs showed a kitchen with cooker, hob, sink and fridge-freezer, a bed, seating and television, plus a separate toilet and shower room.
A Planning Contravention Notice response completed by the appellant in September 2025 said the building had been used as a separate unit of accommodation from March 2025 and had housed family friends from abroad during May and June.
Inspector M P Howell gave the building control material only limited weight. Building regulations and planning control serve different purposes, and the certificate did not show that the building’s planning use and function had been investigated.
The Inspector found on the balance of probabilities that the building had been erected and used as a self-contained dwelling. It therefore did not benefit from the householder Class E right relied on by the appellant.
The decision also considered Uttlesford District Council v Secretary of State for the Environment and White, where the presence of domestic facilities was not by itself decisive. The Inspector distinguished it because the facilities at Elmshott Lane sat alongside the PCN response, separate occupation and the lack of access for occupiers of the main house.
Why the Slough garden dwelling fallback failed
The appellant proposed an alternative: retain the same building as a gym and store, with toilet and shower facilities, serving the main house.
The Inspector specifically asked the parties whether that alternative could be dealt with through the ground (a) appeal. Her conclusion was no.
A ground (a) deemed application allows permission to be considered in relation to the whole or part of the matters stated in the enforcement notice. Here, the allegation was the erection and use of a self-contained dwelling. Retaining the structure with a different planning status and function as an incidental outbuilding was not a lesser part of that alleged development. It was a different form of development.
The gym and store proposal therefore fell outside the scope of the deemed application. That, rather than a ruling that a gym could never be acceptable on this site, was the immediate reason the Inspector could not grant the fallback.
Could Class E legalise the building retrospectively?
There is a separate permitted development point beneath the appeal, and it needs to be kept distinct from the Inspector’s ground (a) reasoning.
Government householder guidance explains that Class E permits buildings required for purposes incidental to the enjoyment of the dwellinghouse, but not separate self-contained accommodation or primary living accommodation such as a bedroom, bathroom or kitchen.
The High Court also addressed retrospective permitted development in RSBS Developments Ltd v Secretary of State for Housing, Communities and Local Government & Anor [2020] EWHC 3077 (Admin). The court upheld the application of Article 3(5)(a) where unlawful building operations formed part of an existing building, and rejected the idea that later remedial works could retrospectively make an earlier unlawful development permitted development.
A later Planning Inspectorate enforcement decision at 12 Pilford Road, Cheltenham, appeal APP/B1605/C/23/3328819, put the practical point plainly: permitted development rights cannot be claimed retrospectively simply by making later changes that bring an existing development within permitted development limits. That appeal decision is persuasive rather than binding case law.
Planning Geek analysis: those authorities strongly support the proposition that changing this Slough building to an incidental gym or store would not, by itself, retrospectively turn its original unlawful erection into Class E permitted development. The direct point is temporal: the building operations had to qualify for Class E when they were carried out; a later change of use cannot rewrite that completed development. Article 3(5)(a) is a separate but related restriction on relying on Schedule 2 rights in connection with an existing building while unlawful construction operations remain enforceable. The Slough Inspector did not need to decide either proposition because she had already concluded that the gym fallback was outside the deemed application.
The building is not necessarily doomed
The appeal was dismissed and the notice upheld on 22nd September 2026, but the Inspector varied the compliance period.
The separate dwelling use must cease within six months. The physical removal steps, including demolition, now have a nine-month compliance period.
The reason for that extra time matters. The Inspector expressly said it would allow the appellant to submit an alternative scheme for Slough Borough Council to consider while still leaving enough time to comply with the notice if necessary.
So the appeal does not establish that the building must inevitably disappear. Slough could still consider a retrospective application or another agreed planning solution. Equally, none has yet been approved, and the enforcement notice remains in force.
See Planning Geek’s Class E outbuildings guide, enforcement appeal grounds guide, the RSBS Developments case-law summary and judgment and the locally hosted Slough appeal decision, or see the Planning Inspectorate appeal record.
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