What counts as curtilage for permitted development

Curtilage is the land that goes with your house for planning purposes, and it is not the same as the red line on your title plan. It matters because almost every householder permitted development right in Schedule 2 Part 1 of the General Permitted Development Order 2015 is expressed as something you may build "within the curtilage of a dwellinghouse", and because the 50 per cent rule for outbuildings is measured against the curtilage area.

There is no definition of curtilage in the Town and Country Planning Act 1990. The meaning comes from a run of court decisions, and the practical consequence is that two neighbours with identical title plans can have different curtilages.

Why the title plan does not settle it

Land registry title tells you what you own. Curtilage tells you which land forms part of the house. Those overlap on a standard suburban plot and diverge as soon as the plot gets large or irregular.

A farmhouse sold with 12 hectares has a curtilage of perhaps a quarter of a hectare: the garden, the yard, the parking area and the outbuildings that serve the house. The remaining fields are in the same ownership and are not curtilage. Build a garden room in the middle of one of them and you are outside Part 1 entirely, whatever the title shows.

The reverse also happens. A shared drive, a coal store in a neighbour's ownership, or a strip of land that was conveyed separately in 1960 can still be curtilage if it has always been used with the house.

What the courts actually weigh

Three factors run through the case law: the physical layout of the land and the building, the ownership of the land past and present, and the use or function of the land past and present. No single factor decides it, and the assessment is made at the date in question rather than historically.

The older formulation, still quoted in appeal decisions, describes curtilage as ground used for the comfortable enjoyment of a house, serving the purposes of the house in some necessary or useful manner. A later decision put the emphasis on the land being small and forming part and parcel of the house.

Two working tests follow from that. Does the land read as part of the domestic setting of the house when you stand in it? And does it serve the house functionally, rather than simply belonging to the same person?

An enclosed lawn with a washing line, a shed and a path from the back door is curtilage. A fenced paddock with a field gate onto a lane, reached across the lawn, is usually not, even when the family walks a pony in it.

Land added to a garden after the house was built

Extending a garden into adjoining land is a change of use, and it is development. Where the land was agricultural, the change to residential garden needs planning permission in its own right, and doing it without permission does not create permitted development rights.

Once the change of use is lawful, whether by permission or by the passage of time, the land can become part of the curtilage. But it does not become curtilage automatically on the day permission is granted. The land has to be laid out and used as part of the domestic setting, and a council looking at an outbuilding application will ask when that happened.

This catches people who buy a house with a large garden created informally by a previous owner. If the garden extension was never permitted and the ten-year period for a change of use has not run, the land may be neither lawful garden nor curtilage, and the outbuilding you build on it is unauthorised. A certificate of lawfulness for an existing use under section 191 of the 1990 Act is the way to establish the position.

Paddocks, orchards and severed land

The recurring mistake is treating everything inside the boundary fence as curtilage. Councils look for the domestic boundary within the ownership boundary.

• A paddock separated from the lawn by a post-and-rail fence, with its own gate, is normally outside the curtilage
• An orchard laid out as part of the garden, mown and accessed only from the garden, may be inside it
• A field in the same ownership on the far side of a lane is outside it in almost every case
• A former stable yard converted to garaging and parking for the house is usually inside it
• Land sold off and later bought back sits wherever its current layout and use put it

The practical test is what you would have to change to make the answer obvious. If removing one fence would merge the land visually into the garden, the council will want to know why the fence is there.

Curtilage and the 50 per cent outbuilding rule

Class E of Part 1 permits buildings incidental to the enjoyment of the dwellinghouse, subject to a limit on how much of the curtilage can be covered. The total ground area covered by buildings within the curtilage, other than the original dwellinghouse, must not exceed 50 per cent of the curtilage area excluding the ground area of the original dwellinghouse.

Three things in that sentence trip people up. "Original" means the house as first built, or as it stood on 1 July 1948 if it is older, so a large rear extension does not increase your allowance. Every building counts, including sheds, garages, greenhouses and outbuildings put up by previous owners. And the bigger the curtilage, the bigger the allowance, which is precisely why councils scrutinise curtilage claims on large plots.

Work the calculation before you design. Measure the curtilage on a scaled plan, deduct the footprint of the original house, halve the remainder, then subtract the footprint of every existing outbuilding. What is left is the ground area you may cover. Where the arithmetic is tight, the same care applies to the rest of Part 1, including the depth limits under Class A rear extensions and the volume allowances for Class B roof enlargement.

Illustrative example: a semi-detached house with an original footprint of 65 m² sits in a curtilage of 400 m². The allowance is half of 335 m², which is 167 m². An existing garage of 18 m² and a shed of 6 m² leave roughly 143 m² available. Treat the figures as illustrative and measure your own plot.

Curtilage of a listed building

A separate and stricter meaning applies to listed buildings. Under section 1(5) of the Planning (Listed Buildings and Conservation Areas) Act 1990, an object or structure within the curtilage of a listed building, which formed part of the land since before 1 July 1948, is treated as part of the listed building.

The consequence is severe. A garden wall, a privy, a stable block or a gate pier can be listed by association, and altering or demolishing it needs listed building consent. Householder permitted development rights are also removed or restricted within the curtilage of a listed building for several classes.

If your house is listed, establish the 1948 curtilage from the historic Ordnance Survey edition rather than from the current layout, and ask the conservation officer before touching anything older than the house extensions.

Evidencing the extent on an application

Draw the curtilage as a distinct line on the block plan, separate from the ownership boundary, and label both. Then support it.

1. Historic Ordnance Survey extracts showing the garden layout at successive dates.
2. Aerial photography showing mown garden, hard surfacing and structures.
3. The conveyance or transfer plans if the plot has been divided.
4. A statement describing how each part of the land has been used, and by whom, with dates.

Where the answer carries real cost, apply for a certificate of lawfulness for a proposed use or development under section 192 before you build. That certificate is the only formal way to confirm that works are lawful, and it is considerably faster than an enforcement appeal. Set the supporting case out clearly, in the same way you would structure a Planning Statement for a full application, and include the plan showing the curtilage line. Adding a storey under Class AA raises its own separate tests, so check those limits too.

Enter your postcode on PlanScope to see which documents your householder project is likely to need.

This is general guidance rather than legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.