Almost every house in West London shares a wall, a boundary or a foundation line with a neighbour. That means almost every extension, loft conversion or structural alteration in Hayes, Ealing, Hounslow or Harrow triggers the Party Wall etc. Act 1996. It is not as scary as it sounds, but ignoring it can stop a project dead. Here is what homeowners need to know in 2026.
What is a party wall?
A party wall is a wall shared between two properties – the wall between terraced or semi-detached houses, or a garden wall built astride the boundary. The Act also covers party structures (floors between flats) and, importantly, excavation near a neighbour’s building, even if no wall is shared.
Which projects trigger the Act?
- Loft conversions – inserting steel beams into a party wall, or cutting into it to support the new floor.
- Rear and side extensions – building a new wall on or up to the boundary line, and digging foundations within 3 m of a neighbour’s structure (or 6 m in some cases with deep foundations).
- Removing chimney breasts from a party wall.
- Raising a party wall for a double-storey extension.
- Underpinning or damp-proofing a shared wall.
Painting, plastering, fitting shelves or replacing a kitchen do not trigger the Act.
The process step by step
- Serve notice. You (or your builder on your behalf) give written notice to each affected neighbour – two months before starting work on a party wall, or one month for excavation or a new wall on the boundary. The notice describes the work and includes drawings.
- Neighbour responds within 14 days. They can consent in writing (no further formalities), or dissent. Silence counts as dissent.
- If they dissent, surveyors are appointed. Either one “agreed surveyor” acting for both sides, or one each. The surveyors prepare a Party Wall Award – a legal document setting out how and when the work will be done, a schedule of condition of the neighbour’s property, working hours and access.
- Work proceeds under the award. Any damage is assessed against the schedule of condition and made good at your cost.
How much does it cost?
| Scenario | Typical cost to you |
|---|---|
| Neighbour consents in writing | £0 (notice drafted by your builder or a £100–£200 template service) |
| One agreed surveyor for both parties | £900 – £1,500 |
| Two surveyors (one each) | £1,800 – £3,500 – you pay both |
| Three neighbours on a terrace with an outrigger | Can reach £5,000+ |
| Schedule of condition only | £300 – £500 per property |
The building owner – the person doing the work – pays all reasonable surveyor fees. This is why a friendly conversation with the neighbours before serving notice matters so much: a signed consent saves thousands and weeks.
Tips from our site experience in West London
- Talk first, serve second. Show neighbours the drawings over a cup of tea, explain the timeline and offer to fix anything that gets damaged. Most people in Ruislip, Hayes and Ealing consent when they understand what is happening.
- Serve notice early. Two months is the legal minimum; planning delays mean you can serve notice as soon as drawings exist and start work as soon as the period expires.
- Use one agreed surveyor where possible – it halves the fee and speeds up the award.
- Get a schedule of condition even when neighbours consent. Photographs of existing cracks protect both sides.
- Tell your surveyor about trees and drains. Deep foundations near London clay and tree roots are exactly what the Act is designed to manage.
- Flats: the freeholder and the flats above and below may all be “adjoining owners”.
What if a neighbour refuses to engage?
They cannot stop lawful work, but they can delay it. If a neighbour will not appoint a surveyor within 10 days of a request, you can appoint one on their behalf under section 10 of the Act. If they refuse access for the schedule of condition, the surveyors record that fact in the award.
How GSM Builders Ltd handles party walls
We draft and serve notices for every extension and loft conversion we build, work with your appointed surveyor (or recommend experienced local ones), and schedule the build around the award so nothing is delayed. It is part of the service – see our house extensions and loft conversions pages, or our guide to planning permission in West London.
