Party Wall Act Section 6

The two triggers

Section 6 contains two independent tests. Either can apply on its own. On deeper projects — basements, piling, underpinning — both commonly apply at the same time, but only one notice needs to be served.

The 3 metre rule

The 3 metre rule is the trigger most commonly encountered on residential extension and basement projects. Both a distance test and a depth test must be satisfied.

The three metres is measured horizontally from the nearest part of the adjoining owner’s building — not from the boundary line. The depth test runs from the bottom of their existing foundations, not from their ground level.

For a detailed look at this rule and the practical examples it catches, see the Party Wall Act 3 metre rule guide.

The 6 metre rule

The 6 metre rule applies where excavation within six metres of an adjoining building would cut below a line drawn downwards at 45 degrees from the bottom of that building’s existing foundations. It typically catches deeper works: piled basements, lift pits, and deep underpinning.

The 45-degree line starts at the base of the neighbour’s foundations and runs towards the proposed excavation. If any part of the excavation falls below that line and within six metres of the building, the rule applies.

View

Both the 3 metre and 6 metre rules must be checked on every project that involves excavation near a boundary. Checking one and missing the other is a common source of programme delay.

The section 6 notice

A section 6 notice — required whether the 3 metre or 6 metre trigger applies — is a formal statutory document. Defects in content or service can invalidate it and force re-service, which delays the programme.

• The name and address of the building owner.
• The address of the site on which the works are proposed.
• A description of the proposed excavation, with plans and sections showing depth and position.
• The proposed start date, with at least one month's notice before works begin.

For the general rules on service and timing, see the party wall notice guide.

What happens after service

The adjoining owner has 14 days from service to respond. They can consent in writing, dissent in writing, or do nothing — which the Act treats as a deemed dispute. In a dispute, surveyors are appointed and a party wall award is drawn up before excavation can start.

Schedule of condition

A schedule of condition records the state of the adjoining property before excavation begins. It is not a statutory requirement under section 6, but it is the most practical protection available to both parties if damage is later alleged.

Without a photographic record taken before works start, any dispute about pre-existing defects versus excavation damage becomes difficult to resolve. The award commonly provides for a schedule of condition to be prepared as part of the process.

Common mistakes

• Assuming section 6 only catches basements. Extension foundations within three metres of a neighbour's building trigger the rule just as readily.
• Measuring from the boundary rather than from the nearest part of the neighbour's building.
• Using the neighbour's ground level as a proxy for foundation depth. The test runs from the bottom of their foundations, not the surface.
• Overlooking the 6 metre rule because the 3 metre rule appears to be the only trigger. Both must be checked on every project involving excavation near a boundary.
• Starting excavation during the 14-day response period. That converts a procedural issue into an injunction risk.
• Relying on verbal agreement rather than a written consent or award.