What the Party Wall Act covers
The Party Wall etc. Act 1996 regulates building work that affects a party wall (shared with a neighbour), a party fence wall, an excavation within 3 metres of an adjoining structure that goes below the existing foundation level, or excavation within 6 metres where the new excavation is deeper than a 45-degree line from the adjoining building. In London, almost every terraced or semi-detached extension triggers the Act — at minimum the new foundations are within 3m of the neighbouring property, often the work directly affects the shared party wall (insertion of beams, raising of party wall for loft conversion, cutting in for flashings). The Act is procedural: it sets out the steps for notice, dissent, surveyor appointment and award.
Serving notice
Before any work can begin, the building owner (you) must serve formal notice on the adjoining owner (neighbour). The notice period varies by type: Party Structure Notice for work to the party wall itself — 2 months minimum; Notice of Adjacent Excavation for excavation within 3 or 6 metres — 1 month minimum. The notice must specify: the proposed works, expected start date, the names and addresses of the parties, and the relevant section(s) of the Act being invoked. Notice must be in writing and served in person, by post to the property, or by email if the neighbour has consented to email service. Notice that doesn't comply with these requirements is invalid and you'd have to start over.
Consent, dissent and surveyors
Once notice is served, the adjoining owner has three response options: consent in writing (work proceeds, no further process), dissent and appoint their own surveyor (each party has a surveyor, who together produce an Award), or do nothing within 14 days of notice (deemed dissent — same as explicit dissent). Where each party has their own surveyor, they appoint a third surveyor by agreement, who acts as arbitrator on any disputes between the first two. In practice, where the surveyors are experienced and the work is routine, the two surveyors agree the Award without ever calling on the third. Surveyor fees are paid by the building owner (you) regardless of which surveyor — your own and the neighbour's. Typical total fees on a London terrace extension: £1,200–£2,500.
The Award and what it covers
The Party Wall Award is the formal document signed by the surveyors that authorises the work to proceed. It covers: a schedule of condition of the adjoining property recorded before works start (photos, descriptions, any existing cracks or defects); the agreed method of work for any party wall interventions; access arrangements (where the building owner needs to access the neighbour's land for scaffold or works); programme dates; security for expenses (a sum held by the neighbour's surveyor against any damage); reinstatement requirements. The Award is binding on both parties unless appealed to the County Court within 14 days of service — appeals are extremely rare and almost always unsuccessful on procedure rather than substance.
What happens if you don't comply
Proceeding without serving notice is not a criminal offence but is technically unlawful. The adjoining owner can obtain an injunction to halt the work — a courthouse-level intervention that can cost £15,000–£40,000 in legal fees and weeks of delay. They can also claim damages for any actual harm caused by the unauthorised work. In London, where neighbours are close, attentive and often professional themselves, attempts to proceed without notice are usually detected within days. We never start a project without confirmed Party Wall Awards in place for all affected boundaries — typically 6–10 weeks before site mobilisation we begin the process.
Common scenarios in London projects
Single-storey rear extension on a terrace: foundations within 3m of both neighbours triggers Section 6 notices to both. Loft conversion with steel beams resting on party wall: triggers Section 2 (work to party wall) notice. Mansard or hip-to-gable: same. Knock-through internal wall that is also party wall: Section 2 notice. Side return extension: Section 6 notice to side neighbour, often also Section 2 if the extension wall is to be tied into the party wall. Basement extension: Section 6 notice to both neighbours, often with extensive structural method statements required. Each scenario has standard documentation we maintain in templates; the process is routine when run by an experienced surveyor and contractor.
