In article , JennyC wrote:

Kew has some info:
http://www.rics.org.uk/Property/Resi...ntialproperty/
Trees%20can%20be%20root%20of%20homeowner%20nightm ares.html

Er, those aren't the root sizes, but the distances at which the trees
will extract a lot of water in summer, thus causing subsidence. For
example, birch roots spread for incredible distances and can block
drains at greater than tree height away, but birches are not thirsty
trees and so cause little subsidence.


Regards,
Nick Maclaren.