Most extension and loft conversion disputes with neighbours start the same way: nobody served a Party Wall Notice. The rules are precise, the timelines are fixed by law, and silence from a neighbour counts as a formal dispute, not consent.
The three situations that trigger the Act
The Party Wall etc. Act 1996 applies to three main types of work: altering an existing shared party wall or party structure, building a new wall at or astride the boundary, and excavating within a certain distance of a neighbouring building. Terraced and semi-detached homes very often meet at least one of these tests, so it's worth checking early in planning, not once building has already started.
The 3-metre and 6-metre excavation rules
Section 6 of the Act governs excavation specifically. The 3-metre rule applies if you plan to excavate within 3 metres horizontally of a neighbour's building and your excavation will go deeper than their foundations. The 6-metre rule is a geometry test: it applies if your excavation, within 6 metres, cuts into a 45-degree plane measured downward from the neighbour's foundation level. Most ordinary domestic extensions and basement projects trigger at least the 3-metre rule.
Notice periods — these are fixed by law
- Party Structure Notice (work to an existing shared wall): at least 2 months before starting
- Line of Junction Notice (a new wall on the boundary): at least 1 month before starting
- Adjacent Excavation Notice (Section 6 excavation work): at least 1 month before starting
Work can only start earlier than these periods if the neighbour agrees to it in writing.
Silence is not consent
Once you've served a valid notice, your neighbour has 14 days to respond. If they don't respond at all within that window, the law treats this as dissent — not agreement — and a formal party wall dispute has legally arisen, even though nobody has actually argued about anything. At that point, surveyors must be appointed to resolve the matter through a Party Wall Award.
What a Party Wall Award actually does
If a dispute arises (including through the neighbour's silence), either an agreed surveyor or two separately appointed surveyors produce a Party Wall Award — a binding document setting out how and when the work can proceed, and addressing matters like protecting the neighbouring structure and repairing any damage caused. The building owner carrying out the work is responsible for making good any damage caused to the adjoining owner's property, regardless of what the award says about the works themselves.
How to get this right from the start
- Establish early — ideally at the design stage — whether your project falls under Sections 1, 2, or 6 of the Act.
- Serve the correct notice type, with the correct notice period, on every adjoining owner affected.
- Include the required plans and sections showing depth and position for any excavation notice.
- Keep a written record of when notices were served and any response received.
- If 14 days pass with no response, treat this as a formal dispute requiring surveyor involvement — don't simply proceed as if you have consent.
What this means practically
- The Party Wall Act is entirely separate from planning permission and Building Regulations approval — you may need all three for the same project.
- Notice periods are fixed by statute (1-2 months depending on the work) and can't be shortened without the neighbour's written agreement.
- A neighbour who doesn't respond within 14 days has legally dissented, not consented — proceeding without addressing this properly is a real legal risk.
- You remain responsible for any damage your excavation or works cause to a neighbouring property, regardless of how carefully the award was followed.
Sources
- Anstey Horne — Party Wall Section 6: The 3m/6m Excavation Rules Explained: ansteyhorne.co.uk
- Hourican Associates — Party Wall Act notice periods and process overview: houricanassociates.com
Related Kibbo Tools
- Building Permit Checklist — check permit requirements alongside your Party Wall obligations before starting a room addition or extension.