Al Reynolds wrote:
wrote:

Not quite. If you are excavating within 3m and lower that your
neighbours foundations or within 6m if you are excavating lower than a
line drawn at 45 degrees downwards from the bottom of neighbours
foundations.

True, but foundations for a new extension will almost always be
deeper than for the house it is attached to, because of changes in

True, but irrelevant. It's the depth of the neighbours foundations that
apply. The nearest point of the neighbours structure may itself be a
new extension with deeper foundations.

MBQ