The short answer
It depends on exactly what is being built and where the true boundary lies. A neighbour can usually build up to the boundary on their own land, and the Party Wall etc. Act 1996 even allows a wall to be built astride the line in some cases, with a line of junction notice — but they cannot simply build on your land. Several areas of law apply at the same time: planning permission controls whether they can build at all; ownership and the true boundary decide whose land it is; the Party Wall Act governs building on or near the line; and trespass and nuisance protect your property. Because these overlap, the answer is rarely a simple yes or no.
Why it matters
It helps to separate the different regimes, because each answers a different question:
- Planning permission — whether the build is allowed in principle. It is decided by the council and is entirely separate from ownership; even permitted development has limits near boundaries.
- Ownership and the true boundary — building on your land is trespass; building up to the line on their own land may be perfectly lawful. Where the line actually runs is an evidence question.
- The Party Wall Act — a new wall built up to or astride the boundary needs a line of junction notice (section 1); excavation near your foundations needs a notice (section 6); and work to a shared wall needs a party structure notice (section 3).
- Trespass, nuisance and right to light — further protections that can apply.
Because so many laws overlap, this is an area where specialist advice earns its keep — and the foundational question, as always, is where the boundary truly lies, which the evidence has to establish.
What to do now
- Establish where the true boundary runs before assuming anything.
- Check whether the Party Wall Act applies and whether notices are due.
- Check the planning position separately.
- Raise concerns early and in writing, and take advice given the overlapping laws.
Common mistakes
- Assuming planning permission settles ownership or the boundary.
- Assuming a neighbour can never build up to the line.
- Overlooking party wall notices.
- Treating it as purely a planning matter.
When to call Coburns
We establish the true line, identify any Party Wall Act notices, and help you navigate where the different laws overlap — objectively and before positions harden.