My son’s neighbour has planted eight-foot conifers right up against his property. I have been told they could damage the foundations.
The trees’ roots are unlikely to damage your son’s foundations unless his house was built on clay and was put up before 1980, when new regulations about foundations were brought in. If damage were to occur it’s likely the neighbour would be liable if he was aware of the problem, so your son could write to him expressing his concern and, in the event of damage, let his insurers deal with the question of liability. Local authorities have powers to intervene where disputes over high hedges cannot be resolved amicably. The hedge must be more than two metres high, present a barrier to either light or access, and adversely affect the reasonable enjoyment of the property in question.