Disputed boundaries and permitted development measurements

Permitted development limits for a house are measured from the boundary of the curtilage, and a boundary dispute permitted development problem arises because the line on your title plan is not the legal boundary. Land Registry plans show general boundaries only. If your extension relies on being more than 2 metres from the boundary, and the boundary turns out to sit 300mm further in than you assumed, the work is not permitted development and you have built without permission.

This is a bigger risk than most householders realise, because several of the limits in the Order are triggered by short distances.

Why boundaries matter to the limits

Schedule 2 Part 1 of the General Permitted Development Order 2015 contains a set of conditions that turn on proximity to the boundary. The eaves height of a single-storey rear extension is restricted where any part of it sits within 2 metres of a boundary. Outbuildings under Class E are restricted to a lower maximum height within 2 metres of a boundary. Side extensions under Class A are limited by width relative to the original house, and the enlarged dwellinghouse must not extend beyond a wall forming a principal elevation fronting a highway.

Read together, those conditions mean a few hundred millimetres decides whether a scheme is permitted. And unlike a planning judgement, this is binary. There is no room for an officer to take a view.

Curtilage adds a second layer. The relevant boundary is the boundary of the curtilage of the dwellinghouse, not the boundary of the registered title. Where a garden has been extended into land bought later, or where part of the title is a paddock rather than garden, the curtilage boundary and the title boundary can be in different places.

Measuring from the boundary of the curtilage

Work from a measured survey, not from a scaled plan. A topographical survey that picks up the physical features, fences, walls, hedges, kerbs and the face of the house, gives you something to argue from.

Then decide which physical feature you believe marks the boundary and say why. The usual candidates are the face of a wall, the centre line of a hedge, the posts of a fence, or an established line of use. None of them is automatically correct. A fence may have been put up on one owner's land, leaving a strip beyond it still in their ownership.

Where the answer is close, design out the problem. Pulling an extension 400mm off the assumed line, or dropping the eaves to 2.5 metres so the proximity condition no longer bites, costs very little at design stage and removes the issue completely. Designing to the limit with no margin is the decision that creates the dispute.

Title plans and their accuracy

Section 60 of the Land Registration Act 2002 states that the boundary shown on a registered title is a general boundary and does not determine the exact line. The red edging on a title plan is drawn over an Ordnance Survey base at a scale where the line itself can represent a real-world width of several hundred millimetres.

So a title plan tells you roughly where the boundary runs and who owns which side. It does not tell you where to put a wall.

Two routes give more certainty:

1. An application to HM Land Registry for a determined boundary, which fixes the exact line on the register. It needs a plan to a high standard of accuracy and evidence, and neighbouring owners are given notice and can object.
2. A boundary agreement with the neighbour, recorded in writing with a plan, which can then be noted on the titles. This is faster and cheaper where relations are good.

The original conveyance is often more useful than the register. Pre-registration deeds sometimes carry a plan drawn at a larger scale with measurements written on it, and where the parcel has not changed shape since, that plan is strong evidence.

Unregistered strips and access ways

Old estates frequently left narrow strips of land unregistered: a former ditch, a verge, the site of a removed hedge, or the half-width of a service lane. These strips sit between two titles and belong to neither, or belong to a developer's company that was dissolved decades ago.

If a strip lies between your garden and your neighbour's, the boundary of your curtilage is at the strip, not at the fence beyond it, unless you have acquired the strip by adverse possession and can prove it.

Adverse possession of registered land under Schedule 6 to the Land Registration Act 2002 runs on a ten year period with a notice procedure that gives the registered owner a chance to object, and the rules for unregistered land differ. This is a matter for a conveyancing solicitor, not for a planning consultant, and it takes months rather than weeks.

The shared access way is the other recurring case. A drive shared between two houses, with a right of way over it, is often owned to the centre line by each. Building a side extension that projects onto the half you do not own, or that obstructs the right of way, is a civil problem that planning permission does not fix.

Evidence where the boundary is unclear

Assemble the record before you build, because it is far harder to reconstruct afterwards.

What carries weight: the original conveyance plan and any measurements on it, historic Ordnance Survey editions showing the feature over time, aerial photography with a known date, a measured survey by a surveyor with the methodology stated, photographs of the fence line with datable context, and statutory declarations from long-standing residents or previous owners describing where the fence has been and who maintained it.

What carries little weight: a neighbour's recollection with nothing to support it, the position of a fence erected in the last few years, and the red line on a modern title plan.

Where the extension is close to the line, a short letter to the neighbour setting out your understanding of the boundary, with the survey attached, is worth sending. Silence is not agreement, but a documented attempt to agree helps enormously if the matter later goes anywhere.

Effect on a lawful development certificate

A lawful development certificate under section 192 of the Town and Country Planning Act 1990 is the only formal way to confirm that proposed works are lawful. The council decides it on the evidence, and the burden of proof is on the applicant.

If the boundary position is uncertain, that uncertainty transfers straight into the certificate application. The council can refuse where it is not satisfied on the facts, and a refusal is not a finding that the works are unlawful, only that you have not proved they are lawful.

Two practical consequences follow. First, a certificate granted on the basis of a stated boundary position does not bind your neighbour, who is not a party and can still bring a civil claim about the line. Second, if the boundary is genuinely in dispute, a full householder planning application is often the faster route, because it puts the question of acceptability rather than the question of measurement in front of the council. A Planning Statement setting out the policy case then does the work that the certificate cannot.

Resolving the position before building

Do this in order, and do it before the groundworker arrives.

1. Commission a measured survey that picks up every physical feature near the line.
2. Obtain the office copy entries and title plan for both properties, and the original conveyance if you can get it.
3. Compare the survey against historic mapping and aerial photography for the same features.
4. Write down the boundary position you are relying on and the evidence for it.
5. Share it with the neighbour, in writing, with the plan.
6. If they disagree, either redesign to remove the dependency or obtain advice on a determined boundary application.

Redesigning is almost always cheaper than fighting. It is also the only option that eliminates the risk rather than transferring it.

Two related traps sit next to this one. A garden building can lose its permitted development status for reasons that have nothing to do with boundaries, as our note on when a garden office stops being incidental explains, and the limits on external alterations catch people out too, which is covered in painting the outside of a house and where the right stops. If you end up making a full application, the 66 report types by category show what else a householder scheme can attract.

This is general guidance, not legal advice. A lawful development certificate is the only formal way to confirm that works are lawful, and boundary ownership is a legal question for a solicitor. 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.