Legal Question in Real Estate Law in California

First of all, a tree that shares a boundary line belongs to both neighbors, not just your neighbor because you say so. �Trees whose trunks stand partly on the land of two or more coterminous owners, belong to them in common.� (Civ. Code � 834.)

Second, your neighbor can build his fence anywhere he wants, as long as it is on his property. He needs your permission to build it on your property.

Mr. Roach is mostly right, including his statement that the tree belongs to both of you. However, there is an ancient provision in the Civil Code, harking back to days (1872) when most properties were farms, not city houses. That's Civil Code section 841(2). It says "Coterminous owners are mutually bound equally to maintain.......The fences between them, unless one of them chooses to let his land lie without fencing, in which case, if he afterwards incloses it, he must refund to the other a just proportion of the value, at that time, of any division fence made by the latter."

Now what the heck does all that mean?

Courts have held that neighbor X doesn't have to pay half the cost of the fence between X and Y unless and until X's property is completely enclosed by something -- fence, buildings, hedges, etc. -- so that (for example) cattle, dogs, children, etc. can't get in or out. So, unless the proposed fence is gonna result in your property being "inclosed" (to use the 1872 spelling), you don't have to participate in the cost.