When does an extension involve the Party Wall Act?
The Party Wall etc. Act 1996 can apply to extensions where the proposed works affect neighbouring properties.
Three common situations are:
- Excavating foundations close to a neighbouring building.
- Building a new wall at the boundary between two properties.
- Cutting into, raising or otherwise altering an existing party wall.
An extension doesn't automatically require a Notice simply because it is close to a neighbour. The proposed construction details determine which provisions may apply.
The 3 metre rule
Under Section 6(1), a Notice is generally required where you're excavating within 3 metres of a neighbouring building or structure and your excavation will go deeper than the bottom of its foundations.
This is particularly relevant to rear extensions on terraced and semi-detached properties.
The distance alone doesn't establish whether a Notice is necessary. The relative depth of the existing and proposed foundations also matters.
Section 6(1) — both distance and excavation depth matter.
Illustrative diagram — not to scale.
The 6 metre rule
Section 6(2) covers certain deeper excavations within 6 metres of a neighbouring building or structure.
It applies where the excavation crosses a line projected downwards at 45 degrees from the bottom of the neighbouring foundations, towards the proposed excavation.
This can be relevant to basements, deep foundations and some other excavation works.
Again, being within 6 metres doesn't automatically mean a Notice is needed.
What about building at the boundary?
Section 1 deals with constructing new walls at the line of junction between properties.
A wall built entirely on your land at the boundary may require a Notice under Section 1(5). Building a new party wall astride the boundary requires the adjoining owner's written consent.
A Party Wall Notice doesn't determine the precise legal boundary between two properties or provide permission to build on someone else's land.
Building at the boundary
Illustrative diagram — not to scale.
When should I arrange Party Wall Notices?
If Notices are required, it's sensible to review the drawings before setting a start date.
The statutory notice periods are generally one month for excavation and line of junction works, and two months for qualifying works to existing party structures.
If an adjoining owner dissents or a dispute is deemed to have arisen, an Award may also be needed before the relevant works proceed.
What should you do next?
If you're planning an extension, send us your architectural and structural drawings. We'll review the proposed works and explain whether Party Wall Notices are likely to be needed.
