Party wall notices: when you need one and what happens next
Which works need a party wall notice, the periods for sections 1, 2 and 6, what happens when a neighbour does not reply, and how the 3m and 6m rules work.
The Party Wall etc. Act 1996 is not planning and it is not building control. It is a separate piece of law that applies between you and your neighbour, and it has its own timetable — one that can hold up a job by two months if it is picked up late.
It gets missed constantly, usually because the work does not sound like it involves a party wall. Digging foundations for a rear extension on a terrace almost always does.
Three sections, three notice periods
The Act covers three distinct situations, and each has its own notice period. All three periods run before work can start, not before it is finished.
What triggers which notice
- Section 1 — building a new wall up to or astride the boundary. One month's notice.
- Section 2 — work to an existing party wall: cutting in for a beam, inserting a damp proof course, underpinning, raising it, taking it down and rebuilding, cutting off projections. Two months' notice.
- Section 6 — excavating near a neighbour's building. One month's notice.
The 3-metre and 6-metre rules
Section 6 is the one that catches extensions, and the trigger is geometric rather than obvious.
The 3-metre rule: you are excavating within 3 metres of a neighbour's building or structure, and going deeper than the bottom of their foundations. On a Victorian terrace with shallow foundations, a standard 900mm trench is usually deeper.
The 6-metre rule: you are excavating within 6 metres of their building and any part of your excavation falls below a line drawn downwards at 45 degrees from the bottom of their foundations. This one applies to deeper work — piles, basements, retaining structures.
What happens after you serve
The adjoining owner has 14 days to reply in writing. They can consent, in which case you proceed. They can dissent and appoint a surveyor, in which case an award is drawn up.
Or they can do nothing — and doing nothing is the outcome to plan for. Under sections 2 and 6, no reply within 14 days means a dispute is deemed to have arisen. You are then in the surveyor process anyway, having lost two weeks getting there. If you know a neighbour is away, abroad, or simply the sort who does not open post, serve early.
The award, and who pays
Where there is a dispute, surveyors produce a party wall award: what may be done, how, when, and a schedule of condition recording the neighbour's property before work starts. That schedule is the thing that protects you as much as them — it is the evidence when a crack that was already there gets blamed on your build.
The building owner — the one doing the work — normally pays the surveyors' fees for both sides. That is the default position, not a negotiation.
Notices expire
A party wall notice is valid for one year. Serve too early on a job that then stalls for planning, drawings or funding and you serve again.
The sensible window is once the design is fixed and the programme is real, and at least two months before you want steel over an opening in a shared wall.
If you skip it
There is no criminal penalty and no council enforcement. The exposure is civil: the adjoining owner can seek an injunction stopping the work, and if anything is damaged you are arguing about causation without a schedule of condition to point at.
An injunction on a job that is open to the weather is the most expensive thing that can happen on a domestic build.
Where this comes from
Everything on this page was checked against the primary source in September 2026. Regulations, designations and thresholds change, and nothing here is a substitute for advice on your own property or contract. If you spot something that has moved, tell us and we will correct it.
The sources are listed opposite. They are the published guidance and legislation themselves rather than a summary of them, so you can check any of it directly.
Common questions
Questions on this
Do I need a notice for a rear extension on a semi-detached house?
Usually yes, under section 6, because the foundations go within 3 metres of next door and deeper than theirs. Whether section 2 also applies depends on whether you are cutting into the shared wall — forming an opening or bearing a steel on it does trigger it.
Can my neighbour stop the work?
No. They can dissent, which puts the work into the surveyor process, and the award will set conditions — working hours, access, protection, a schedule of condition. What they cannot do is refuse the work outright. The Act exists to let it happen, with safeguards.
Who pays for the surveyors?
Normally the building owner — the person having the work done — pays for both sides. It is the standard position under the Act, so budget for it rather than treating it as something to argue about later.
Does the builder serve the notice?
The duty is the building owner's, not the contractor's. We will tell you when a job triggers the Act and when the notice needs to go out to keep the programme, but the notice comes from you or from a party wall surveyor acting for you.
Where this applies
The work this affects
- Home extensions Single and two-storey rear, side and wraparound extensions, from first survey to building control sign-off.
- Structural works & underpinning Steels, load-bearing wall removal, underpinning and remedial work to existing structures.
- Loft conversions Dormer, hip-to-gable and rooflight conversions, including the structural work and the staircase.
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