What is the Party Wall Act 3m rule?

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.

What is the 6m rule under the Party Wall Act?

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.

What is a Section 2 Party Wall Notice?

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.

What happens if my neighbour doesn't respond to a party wall notice?

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.

How much does a party wall surveyor cost?

Party wall surveyor fees in the UK typically range from £800 to £1,500 per neighbour for straightforward cases (rear extension). Complex cases (basements, multiple neighbours) can cost £1,500-£3,000+. The building owner normally pays the surveyor fees for both parties. Using an agreed (single) surveyor is usually cheaper than appointing two separate surveyors.

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.

Type of Work

What building work are you planning?

Distance to Boundary

From your excavation to the boundary

Your Excavation Depth

Depth of your proposed foundations/excavation

Neighbour's Foundation Depth (est.)

Typically 1m for standard strip footings

Building on the boundary line

New wall on the line of junction

Building astride the boundary

Wall straddles the boundary line

Surveyor Fee Estimate (optional)

Estimated party wall surveyor cost

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 distance to boundary, excavation depth relative to adjacent foundations, and the type of work.

The rules

3m Rule: Within 3m AND deeper than neighbour's foundation
6m Rule: Within 6m AND below 45° line from neighbour's foundation
Section 1: New wall on or astride the boundary
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

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.