Legal Question in Real Estate Law in California

The answer here is it depends. You may sever the roots, but only if the roots are in fact causing damage. Any severace must be done reasonably (which may mean by a professional).

If you do so reasonably sever the roots, the owner of the encroaching tree is liable for the actual out-of-pocket expenses incurred as a direct result of his tree's encroaching roots.

However, if you fail to act reasonably and negligently sever the roots and therefore, in turn, seriously injure or kill the trees in question, you neighbor may sue you.

There is a case on this point: Booska v. Patel (1994) 24 Cal. App. 4th 1786. In this case, the plaintiff claimed his neighbor negligently cut the roots of his tree, necessitating the tree's removal. The neighbor claimed he had an "absolute right" to cut the tree roots any way he wanted because they were uprooting his driveway. The Appellate Court disagreed and held that a homeowner's right to manage his own land must be "tempered by his duty to act reasonably."

Therefore, so long as the trees are causing actual damage to your driveway, I would say you have a right to sever the roots so long as you do reasonably.

I would suggest talking with your neighbor on this point, as well as meeting with an experienced real property attorney who may be able to aid you on this matter.

Good luck!

I agree with the previous answer's interpretation of the reasonableness requirement of Booska v. Patel. However, the right to sever trespassing roots and limbs does not depend upon their doing damage. Trespassing roots and limbs can be trimmed whether they cause damage or not. The fact that damage is being caused does, however, give you a right to sue for damages.

One suggestion regarding the "reasonableness" requirement is to retain a licensed arborist to look at the situation and advise whether the proposed root trimming is likely to cause permanent harm to the trees. Try to get the arborist and the concrete contractor there at the same time and to agree on how to do the trimming (or removal) so as to have the minimum impact.

If any work on the neighbor's side of the property line is needed and the neighbor won't cooperate voluntarily, you are looking at more than just a simple tree-trespass situation, and are going to have to go to court with a complaint for trespass and/or private nuisance. The self-help provision of tree-trespass law only allows removal of the roots or limbs that actually cross the property line, and if entire trees growing on the neighbor's property must be removed, you cannot do this yourself without a court judgment.

Also, if you use the self-help measures, you will have to pay for them yourself 100% (unless, of course, the neighbor volunteers to pay part or all of the cost). If you expect cost participation, you'll have to sue, but you should be able to demand and get all your costs and expenses except attorney's fees. This may be covered by the neighbor's homeowner's insurance.

I recommend negotiating some kind of deal with the neighbor based on the foregoing answers and the input of the arborist abd concrete contractor rather than going to court. Get it in writing.