Does the Party Wall Act apply to my rear extension?
In England and Wales, often yes: when you build on or astride the boundary, work to a shared wall (such as cutting in a flashing or steel), or dig foundations within 3 metres of a neighbour's building to a lower depth than theirs, or within 6 metres in some deeper cases.
What notice do you have to give?
Two months before work to a party wall or structure, and one month before excavation or building a new wall on the line of junction. Neighbours have 14 days to consent or dissent. If they consent in writing, no surveyors are needed.
What if a neighbour dissents?
Each owner appoints a surveyor, or both agree on one, and the surveyors produce an award setting out how the work will be done and recording the condition of the neighbour's property. The building owner normally pays the surveyors' reasonable fees, which is why we budget £700 to £1,500 per neighbour as an allowance.
Scotland and Northern Ireland
Scotland has no Party Wall Act. Work to shared walls is governed by property law and the title deeds, so we agree access and protection with neighbours in writing before work begins.
Northern Ireland has no Party Wall Act. Shared-wall work relies on agreement with your neighbour and the general law, so we put access and protection arrangements in writing before starting.
About this guide
Written by the Rear Extensions design team and checked against GOV.UK, Welsh and Scottish Government and Northern Ireland guidance in November 2026. It is general guidance, not legal advice; we confirm the rules for your house at the survey.