• three-metre notice: if the excavation will be within three metres of any part of the neighbour's building, and those excavations will go down lower than the bottom of the foundation of the neighbour's existing property, then notice has to be given;
• six-metre notice: if the proposed works are within six metres of a neighbouring building then more complex provisions apply. Basically, you ascertain how deep the proposed excavations will be; from the bottom of those excavations you then go down (at an angle of 45°) towards the neighbour's property. If that 45° line meets any part of the neighbour's foundations, then the landowner has to serve a notice on the neighbour. The end result is that it is possible for the landowner's new excavations/foundations to be deeper than his neighbour's foundations without the neighbour having to be given any party wall notice (unless, of course, the works will be within three metres of the neighbour's building - in which case a three-metre notice will have to be served).

Party walls are a complex area and expert advice is usually needed. As we noted in our June 2004 issue (p21), the best book on the topic is Party Walls - Law and Practice (Stephen Bickford-Smith and Colin Sydenham; Jordans; £45; 2nd Edition). There are two introductory leaflets on the www.odpm.gov.uk site. © Practical Lawyer