The Party Wall etc. Act 1996 applies whenever you build on or against a shared wall, cut into it for beams, dig within 3 m of a neighbour's foundations, or build on the boundary. You must serve written notice one or two months before work starts. If the neighbour consents there is no cost; if they dissent, surveyors produce a party wall award, typically £1,000–£3,000 per neighbour.
When the Act applies
Almost every extension or loft on a London terrace or semi triggers the Act. Three types of work are covered: building a new wall on or astride the boundary (a line of junction notice); work to an existing party wall such as cutting in steel beams, raising it for a loft or removing a chimney breast (a party structure notice); and excavating within 3 m of a neighbour's building to a depth below their foundations, or within 6 m where the excavation would cut a 45° line from their footings (an adjacent excavation notice).
Detached houses are only affected when you dig near the boundary or build up to it. Flats are covered where the works affect floors, ceilings or walls shared with other flats.
Serving notice
Notice must be served in writing on every adjoining owner, including freeholders and long leaseholders of neighbouring flats. Party structure notices need two months' notice; line of junction and excavation notices need one month. The notice must describe the work and, for excavations, include drawings showing the depth.
The neighbour has 14 days to respond. They can consent, dissent and appoint their own surveyor, or dissent and agree to a single shared surveyor. No response counts as dissent, so the surveyor process starts automatically.
The party wall award
If a neighbour dissents, the appointed surveyors inspect both properties, record their condition in a schedule of condition with photographs, and produce a party wall award that sets out how and when the work may be done, working hours, protection measures and who pays for what. The building owner pays all reasonable surveyor fees, typically £1,000–£3,000 per neighbour, or more for basements.
The award protects you as much as the neighbour: the schedule of condition is the evidence if a crack is later blamed on your work.
Avoiding delays
Talk to your neighbours before the formal notice arrives, show them the drawings and explain the programme. Most consent, and many agree to a single surveyor, which halves the cost. Serve notices as soon as the structural design is fixed, ideally while the planning application is being decided, so the two-month period runs in parallel. ICV Buildings prepares and serves the notices as part of our pre-construction service.
Frequently asked questions
- Can my neighbour stop my extension?
- No. The Act gives them the right to have the work supervised by a surveyor and to be compensated for any damage, but it does not give them a veto. Planning objections are a separate matter.
- What if I start work without serving notice?
- The neighbour can apply for an injunction to halt the work, and any damage will be assumed to be your responsibility. Serving notice late is always better than not at all.
- Does a loft conversion need a party wall notice?
- Yes, on a terrace or semi. The steel beams bear on the party wall and the wall is usually raised or cut into for the dormer, both of which are party structure works needing two months' notice.