Legal Question in Real Estate Law in California

Re: Tree Roots

You are correct that the neighbor can cut the roots (or limbs) that trespass across the property line at the point where they cross, but must do so in "a non-negligent manner," to quote one leading case. This is usually interpreted to mean that cutting the roots will not injure the tree or cause it to topple in a high wind.

The neighbor's failure to cut the roots or to advise you that damage was taking place could be a factor in mitigation of damages, especially if the damage was occurring in a place you couldn't see from your property, but the neighbor could. Still, I don't think this will absolve you completely.

Without seeing the situation personally, let me suggest that the two of you negotiate a solution that preserves neighborly relations and avoids a lawsuit. Hire a licensed arborist to assess the situation, and then have a couple of contractors look at the physical damage. When you have jointly developed the facts with this professional assistance, share the costs of the experts and the repairs in a way that seems fair. If he will agree to 50-50, I'd say you were getting a good deal. A court might tax 100% of the costs to you, or if it felt the neighbor was remiss in not pointing out an ongoing situation earlier, the court might shift some of the burden to the neighbor, but I doubt much or all unless the situation is unusual.