Class Q curtilage trap: the old farmyard may still be agricultural

A Class Q barn conversion does not automatically turn the whole former farmyard around it into residential garden. A new Somerset appeal has confirmed that land outside the curtilage authorised with the conversion can remain in agricultural use even where it once formed part of the barn’s wider agricultural curtilage.

The decision in APP/E3335/X/24/3353647 is also a useful warning about lawful-development certificates. The Inspector concluded that asking for the extent of a “curtilage” to be certified was the wrong planning question because curtilage describes a legal relationship, not a use of land.

What happened at the Somerset barn?

The appeal concerned a former agricultural barn at Land at 355011, 133865, Martin Street, Baltonsborough, Glastonbury, Somerset.

Somerset Council had granted prior approval in October 2021, reference 2021/1957/PAA, for the barn to change to a dwellinghouse under Class Q permitted development. The approved plans showed the barn together with a proposed residential curtilage around it.

Crucially, the Inspector recorded that the approved curtilage was approximately the same area as the footprint of the barn. When the Class Q development was implemented, the barn and that identified area changed from agricultural use to a single dwellinghouse.

The later certificate tried to extend the curtilage

In February 2024 the owner applied for a Certificate of Lawfulness of Proposed Use, reference 2024/0349/CLP, described as a proposed use “to extend the existing curtilage”. The wider area was enclosed land immediately around the converted barn and the appellant argued that it had historically formed part of the barn’s agricultural curtilage.

Somerset Council refused the certificate on 5 June 2024. The owner appealed under section 195 of the Town and Country Planning Act 1990, arguing in substance that the larger agricultural curtilage should continue as the curtilage of the new dwelling once the Class Q conversion had taken place.

The Inspector disagreed and dismissed the appeal on 27 August 2026.

Class Q has its own narrow curtilage rule

This is where the decision becomes particularly useful. In ordinary planning language, residential curtilage is usually a fact-and-degree question about the relationship between land and a building. Class Q is different because the GPDO gives the right its own restrictive definition.

When the 2021 prior approval was granted, that definition sat in paragraph X of Part 3. In broad terms, Class Q curtilage was the lesser of the land immediately beside or around the agricultural building that was closely associated with and served it, or an area no larger than the land occupied by the agricultural building itself.

The drafting has since moved. Under the current rules the Class Q definition appears in paragraph Q.3, but the important point for this appeal is that the Inspector was dealing with the version that applied to the 2021 prior approval rather than retrospectively applying the 2026 wording.

You can read the current Schedule 2 of the GPDO on legislation.gov.uk and our pre-21 May 2024 Class Q page for the historic regime that applied when this prior approval was granted.

The old farmyard did not become residential land

The Inspector accepted that the larger area may once have been curtilage serving the agricultural barn. That did not mean all of it changed use when Class Q was implemented.

Only the land identified as curtilage for the Class Q development was brought within the permitted change to residential use. The remaining land stayed agricultural. Using that additional land for the purposes of the dwelling would therefore amount to a further material change of use requiring its own planning justification unless it had become lawful by some other route.

So the practical message is simple: Class Q does not automatically turn the whole old farmyard around a converted barn into a garden.

The certificate question was also wrong

There is a second trap in the decision. The application itself was made under section 192, the route for a proposed use or operation, and Planning Geek has a separate guide to a Certificate of Lawfulness of Proposed Use or Development.

In paragraph 6, however, the Inspector explained that an application under section 191(1)(a) concerns the lawfulness of an existing use and that “curtilage” is not itself a use of land. He therefore described the attempt simply to establish the extent of the curtilage as misconceived.

That distinction matters. Instead of asking only “what is my curtilage?”, the planning question may need to be whether the residential use of the additional land is lawful. That will depend on the facts and the certificate route actually being used, so the decision should not be read as saying that every curtilage dispute can be solved by the same form of application.

For existing uses, see our guide to Certificates of Lawfulness under section 191.

Why the line on the Class Q plan matters

A tight residential curtilage can have very practical consequences after a barn conversion. The obvious one is garden use, but the same boundary may affect where domestic parking, patios, sheds, garages and other residential paraphernalia can lawfully spread.

It can also matter when someone later looks at permitted development rights. A dwelling created under Class Q does not enjoy the normal Part 1 householder permitted development rights in any event, and agricultural land beside it does not become domestic land simply because it sits next to the house.

That makes the approved Class Q site plan much more than administrative decoration. Farmers, developers, buyers and their advisers should check exactly what land changed use with the barn, particularly before a sale or before assuming that a larger yard can simply be landscaped and used as part of the home. It is also worth keeping that residential line separate from the holding’s wider agricultural and forestry permitted development rights.

The appeal in one sentence

The barn became a home, but the whole surrounding agricultural yard did not come with it.

The appeal was dismissed. You can read the full appeal decision APP/E3335/X/24/3353647 on Planning Geek.

Created: 1st September 2026 — Class Q curtilage