There are several ways this can be done – if possible a trial hole can be dug but that may be difficult if the building is detached from yours.
Entries for the ‘Exacavation’ Category
Here’s a super helpful flowchart showing the Party Wall process from beginning to end. Some fine detail is left out such as special foundations and addendum awards to make it easier to follow but it represents an excellent graphical representation of where the Building Owners Surveyor, Adjoining Owners Surveyor, Third Surveyor, Party Wall Notices and [...]
A neat little new piece on the BBC a week or two back about the problems of building basements under existing houses and the protection offered [or not offered!] by the Party Wall Act.
The Act grants a right to a building owner to underpin the party wall.
Section 1 of the Act provides a building owner with the right to place foundations on his neighbour’s land. There is no right, however, to place what are known as special foundations (foundations incorporating metal reinforcement) on your neighbour’s land without their prior written agreement.