The Party Wall Act covers excavations which are within 3 metres of an Adjoining Owner’s property, namely their foundations.
If the bottom of the excavation will be lower than the foundations of the adjoining owner’s foundations, then a section 6 notice will need to be served.
It should be noted that for a Three Metre notice to be valid it would need to include a section drawing, which would indicate the depth of the new excavations proposed and its position relative to the adjoining owner’s property.
Depending on what the individual property is like there can be a lot to consider when coming to the right conclusion about the depth of the foundation, an experienced Party Wall Surveyor would take this into consideration depending on what year it was built.
Party wall surveyors can make a good assumption about the depth of an adjoining owner’s foundations by taking into account the date of the property construction.
In some instances, appointing owners ask to confirm the existing foundations against the designs by digging a trial pit.
Section 6(1) of the Party Wall etc. Act 1996 says you must serve notice on your neighbour if you plan to excavate within 3 metres of their building or structure, and to a depth lower than the bottom of their foundations. Both parts matter: distance and depth. Digging footings for an extension, a basement, drainage runs or underpinning within 3 metres of next door’s foundations will almost always qualify, because modern foundations are typically deeper than the shallow footings of older London homes. There is also a 6 metre rule for deeper excavations: if your dig falls within 6 metres and would cut a line drawn at 45 degrees down from the bottom of the neighbour’s foundations, Section 6(2) applies instead. Notice must be served at least one month before excavation starts and must include plans and sections showing the depth of the proposed dig.
First, do not start digging. Serve a valid Section 6 excavation notice with the required drawings – an invalid notice restarts the clock and can invalidate everything that follows. If your neighbour consents in writing, work can proceed, ideally protected by a schedule of condition. If they dissent or do not respond within 14 days, a surveyor (or one each) is appointed and a party wall award records how the excavation will be carried out and what protection the neighbouring building gets. Kingston Surveyors arranges experienced party wall surveyors across London and the UK for exactly this situation – typical fees are set out in our party wall surveyor cost guide, and enquiries are answered the same working day on 0204 579 8270.
