A Hounslow outbuilding appeal has succeeded after a Planning Inspector quashed an enforcement notice requiring a self-contained garden home to stop operating as a separate dwelling. The decision on 30 October 2026 grants retrospective planning permission for the one-bedroom accommodation, subject to a condition securing bicycle storage.
Inspector Siobhán Watson allowed appeal APP/F5540/C/25/3360814 concerning a rear garden building at The Warren in Hounslow. The council had served a notice in January 2025, requiring the independent residential use to cease and kitchen and bathroom fittings to be removed. The appellant challenged the notice on grounds (a) and (d) under the Town and Country Planning Act 1990.
The notable point is that the Hounslow outbuilding appeal failed on the argument that the use had become immune from enforcement through time, yet succeeded when the Inspector assessed its planning merits. The appeal therefore separates two legal routes that are too often treated as interchangeable: proof of established use and permission for use that may otherwise be unauthorised.
Why the Hounslow outbuilding appeal succeeded
The enforcement notice alleged the unauthorised conversion of an outbuilding to a separate self-contained residential unit. It required the occupants to stop using the building as an independent home and to strip out facilities associated with that use. The Inspector corrected the notice’s description, replacing the word ‘conversion’ with ‘use’, because the alleged breach needed to identify a legally relevant change of use, rather than employ terminology that might obscure what was being enforced.
The garden building contained a compact combined living, dining and kitchen area, a bedroom and bathroom facilities. The Inspector described accommodation suitable for one or two people. The building was reached by a side gate and stood at the end of a long rear garden. The appeal was not about whether a family member could use an ordinary ancillary annexe while remaining part of the host household; the proposal was assessed as a genuinely separate dwelling.
In the Hounslow outbuilding appeal, the Inspector accepted that another household living in this small unit would not cause an unacceptable increase in neighbour disturbance. She also found that the long garden, existing boundaries and nearby structures meant the additional residential use would not produce material harm to privacy or local character. Those conclusions were specific to the size and layout of the site.
The four-year immunity case did not succeed
Ground (d) of an enforcement appeal concerns whether enforcement action was already out of time on the date the notice was issued. For an unauthorised change of use to a single dwellinghouse beginning before 25 April 2024, the former four-year rule can remain relevant under the transitional provisions. For a relevant use beginning on or after that date, the ordinary period is ten years. These are statutory limits, not permissions granted by a planning authority.
The appellant produced tenancy agreements and accounts of occupation extending back to 2017 or 2018, together with older invoices for building work. However, the material did not tell a consistent story about who had lived in the outbuilding and when. Some declarations and notices suggested family occupation at dates that did not align with the tenancy documents, while council visits recorded a different pattern of residents.
The Inspector concluded that the evidence did not demonstrate continuous independent residential use for the required four years before the notice of 17 January 2025. The Hounslow outbuilding appeal therefore failed on ground (d), which is important: it was not allowed because the unit had proved an established, immune planning use. Our guide to living in a garage or outbuilding explains why proof of continuous use and the relationship with the original home matter.
Permission was granted on the planning merits
The separate ground (a) argument asked whether planning permission ought to be granted for the development described by the enforcement notice. That allowed the Inspector to consider the site’s character, neighbour amenity, waste and cycle storage, and the relevant policies of the Hounslow Local Plan. An unsuccessful ground (d) did not mean ground (a) was bound to fail.
On neighbour amenity, the council raised concerns about disturbance from an additional household and loss of privacy. The Inspector considered the small occupancy capacity, distance within the garden, fencing and a wall along the boundaries. She observed nearby garden buildings and concluded that the additional activity would not be particularly disturbing and that the window arrangement did not justify refusing permission on overlooking grounds.
The Inspector also distinguished the use of the structure from its physical existence. As she put it in the official appeal decision, Only the use of the building is enforced rather than the building itself.
The garden building would therefore remain even if the notice stood. Without an adequate explanation of why the residential use itself harmed suburban character, the council’s character objection did not persuade her.
This is not a general rule that every detached garden home is acceptable. A separate dwelling ordinarily needs planning permission if its creation involves a material change of use, and the size, privacy, access, drainage, character, amenity and development plan consequences may be quite different on another plot. The enforcement notice guidance also explains why the precise allegation and appeal grounds must be examined before responding.
Waste and cycle parking were addressed
The council argued that the application did not show adequate waste handling or cycle facilities. The Inspector found existing bins neatly stored near a shed, with ample physical room for ordinary refuse and bicycle storage. She did not accept that this small dwelling required an on-site waste processing facility. The outcome depended on practical arrangements rather than a rigid assumption that every separate unit requires an extensive new storage building.
The Hounslow outbuilding appeal was nevertheless allowed subject to an enforceable requirement. Within three months of the decision, a scheme for the covered and lockable storage of one bicycle, including an implementation timetable, must be submitted for the council’s written approval. The approved storage must then be provided to the agreed timetable and remain available for bicycles.
How the Local Plan policy was applied
Hounslow Local Plan policy SC1(q) contains a presumption against self-contained residential units within the curtilage of existing homes where the development would conflict with other plan policies. The Inspector found no unacceptable harm under the relevant amenity, design or transport policies and therefore concluded that the proposal did not trigger the policy conflict relied upon by the council.
That distinction matters for the Hounslow outbuilding appeal because it was not enough for the council to point to a general policy preference against garden housing. The Inspector tested whether the specific change of use conflicted with the plan’s other requirements and found that it did not. The decision grants permission for this unit; it does not rewrite the Local Plan for all garden sites.
What property owners should take from the decision
Someone facing enforcement over a separate garden home should first establish exactly what the notice alleges. Was the complaint the building work, a material change to independent dwelling use, breach of a condition or some combination? They should then match each available appeal ground to the evidence it requires. A timeline of occupation alone will not make a poor planning scheme acceptable, while an acceptable scheme may still need express planning permission.
The Hounslow outbuilding appeal gives a particularly clear example of the two tracks. The evidence of four years’ continuous use was not sufficiently consistent, so immunity failed. However, a small dwelling in a large garden was found acceptable on its merits, and the Inspector quashed the notice while granting permission. That is a site-specific appeal outcome, not a new permitted development right.
The decision and source
Appeal APP/F5540/C/25/3360814 was decided by Inspector Siobhán Watson on 30 October 2026. The official Planning Inspectorate case record contains the decision. The exact quotation here is from the Inspector’s reasoning and is reproduced under the Open Government Licence v3.0. The appeal decision is also available on AppealBase.
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