When do I need a Party Wall Act notice?

You need to serve notice if: building on or at the line of junction (boundary) with a neighbour (Section 1), carrying out work on an existing party wall or structure (Section 2), or excavating within 3m or 6m of an adjoining building below their foundation level (Section 6). The Party Wall etc. Act 1996 applies to England and Wales.

What is the 3m/6m excavation rule?

The 3m rule: if you excavate within 3m of a neighbouring building and go deeper than their foundations, a Section 6 notice is required. The 6m rule: if you excavate within 6m and the excavation goes below a 45-degree line drawn from the bottom of their foundations, notice is also required. These rules protect neighbours from subsidence.

Who pays for party wall surveyors?

The building owner (the person doing the work) pays all surveyor fees, including the adjoining owner's surveyor. If both parties agree on a single 'agreed surveyor', costs are lower. Typical surveyor fees range from £800–£1,500 per adjoining owner for simple extensions, rising to £3,000+ for basements or complex work.

What happens if my neighbour does not respond to the notice?

If the adjoining owner does not respond within 14 days, they are deemed to have dissented. This means party wall surveyors must be appointed. Do not proceed without serving notice — ignoring the Party Wall Act can lead to injunctions, compensation claims and difficulties selling the property.

Can I do an extension without a Party Wall notice?

Yes, if your extension is not on the boundary, does not affect an existing party wall, and excavation does not go below neighbouring foundations within 3m/6m. Even when notice is not legally required, it is good practice to inform neighbours of your plans and keep a record of the condition of their property before work starts.

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Extension Party Wall Calculator — Notice Requirements

Determine Party Wall Act notice requirements for UK extensions based on distance from boundary, work type and excavation depth including 3m/6m rules.

Type of work

Distance from boundary

Number of adjoining owners

Excavation depth

Neighbour foundation depth (est.)

How We Calculate This

This calculator checks whether your extension triggers Party Wall Act 1996 notice requirements based on the work type, boundary distance and excavation depth.

Notice types

Section 1: Building on the line of junction (boundary)
Section 2: Work on an existing party wall or structure
Section 6: Excavation within 3m or 6m of adjoining building

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.