How many times has the neighbor's tree roots caused concrete and water supply line damage to the insured’s property? The rule in California and many jurisdictions used to be that our insured could simply cut the tree roots on his property. However, the current rule in California and developing rule in other states is that our insured must use reasonable care in removing the tree roots. For example, has the insured requested the neighbor to trim the tree or remove the roots prior to the loss? If not, that may be a bar to subrogation.
On the other hand, if the insured has requested such, even though it is not in writing, then the neighbor, as owner of the tree, has to exercise reasonable care in remedying the problem or the neighbor/tree owner is liable for the damage to the insured’s property.
In addition, refer to ANSI A300-2000, for American National Standard for Tree Care Operations--Tree, Shrub and Other Woody Plant Maintenance-Standard Practices. Contact ANSI at 11 West 42d Street, NY, NY 10036 or http://www.ansi.org/