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Party Wall Checker
Check if your building work triggers a Party Wall Act notice. Covers the 3m rule, 6m rule, excavation depth vs adjacent foundations, and Section 1/2/6 notices.
Horizontal distance from your excavation to the neighbour's building or structure (the Act measures from their wall, not the boundary)
Depth of your proposed foundations/excavation
Typically 1m for standard strip footings
New wall on the line of junction, built wholly on your own land — Section 1(5) (no neighbour consent needed)
Party wall straddling the boundary — Section 1(2) (your neighbour's consent is required)
Estimated party wall surveyor cost
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How We Calculate This
This checker assesses whether your building work triggers any of the three sections of the Party Wall etc. Act 1996. It checks the horizontal distance to the neighbour's building or structure, your excavation depth relative to their foundations, and the type of work. Note that the Act measures the 3m and 6m distances from any part of the neighbour's building or structure — not from the boundary line itself.
The rules
3m Rule: Within 3m of the neighbour's structure AND deeper than their foundation
6m Rule: Within 6m AND below the 45° line from the bottom of their foundation
Section 1(2): New party wall astride the line of junction — neighbour's consent required
Section 1(5): New wall on the line of junction but wholly on your own land — no consent needed
Section 2: Works to an existing party wall
This is a guidance tool only. Always consult a party wall surveyor for formal advice.
Notice periods
- Section 1 (new wall): 1 month notice
- Section 2 (party wall works): 2 months notice
- Section 6 (excavation): 1 month notice
- Neighbour has 14 days to respond (consent or dissent)
Frequently Asked Questions
The 3m rule (Section 6) states that if you plan to excavate within 3 metres of a neighbouring building or structure, and the excavation will go deeper than the bottom of the neighbour's foundation, you must serve a Party Wall notice at least 1 month before starting. This applies to extensions, basements, and any significant groundworks.
The 6m rule (also Section 6) applies when excavating within 6 metres of a neighbour's building. A notice is required if the excavation would cut below a 45-degree line drawn downwards from the bottom of the neighbour's foundation towards your excavation. This catches deep excavations such as basements that could affect nearby structures.
A Section 2 notice covers works to an existing party wall or party structure. This includes cutting into the wall, raising or lowering it, removing chimney breasts, inserting a DPC, underpinning, and similar works. You must serve notice at least 2 months before starting work. The neighbour can consent or dissent.
If your neighbour does not respond within 14 days, a dispute is deemed to have arisen under the Act. You must then appoint a party wall surveyor (or agreed surveyor) to prepare a Party Wall Award. This documents the work, sets out conditions, and records the condition of the neighbour's property before work begins.
As an indicative guide to 2026 UK market rates (HomeOwners Alliance and industry cost guides — fees are not fixed by the Act and vary by region and complexity), a single agreed surveyor for a straightforward rear extension with one neighbour is roughly £1,000–£1,500, while two separate surveyors or complex cases (basements, multiple neighbours, London/South East) can run to £3,000+ per neighbour. The building owner normally pays the surveyor fees for both parties, and using an agreed (single) surveyor is usually cheaper than appointing two separate surveyors.
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Last updated: March 2026
Verified against UK standards · estimates only, confirm with your supplier.