"MrCass" wrote in message
...

Is it true if you cut down a large old tree in the garden, will it
affect the foundations of the house? Its about 35 feet away but its a
big old walnut tree


It depends on whether your house's foundations rest on a shrinkable
sub-soil, mainly meaning clay.

A sub-soil such as clay expands if wet and contracts if dry. A large old
tree's root system will probably be extracting significant quantities of
moisture from the sub-soil. Hence, if the tree is felled, it will cease
drying out the subsoil, and moisture content may rise. If the subsoil is
clay, it will then tend to expand, and, if foundations are resting on it, it
could lift the foundations, a process known as 'heave'. If 'heave' occurs
under part of a building's foundations, this could result in structural
damage, e.g. cracking of foundations and walls.

If the trees roots go under your foundations and the sub-soil is clay, their
may be a risk of 'heave' if the tree is felled.