Legal Question in Landlord & Tenant Law in California

You can either try to take the matter to a community mediation process or I recommend getting three estimates on the cost of repairing the fence. You should present a proposal for having the fence repaired and ask the neighbors if they will pay for their share of the expense (1/2). You may want to consider just reconstructing the fence both on your side of the property line only. If you opt to replace the fence but have no written understandings from the neighbors, I recommend doing a formal demand (i.e. certified mail notice); make the repairs and send the neighbors a bill for their share of the costs. If they do not respond in a timely fashion (30 days) take the matter to court (either Small Claims or Limited Civil) and if they do not respond, take a default judgment and then file a lien against the neighbors' property.

Mainly you want to consult with a real estate law attorney who would help you prepare a letter to the neighbors asking them to at least come to the table.I would also find out what's up with the neighbors who may have some challenges that do not allow them to address the fence issue. There is a lot of room to negotiate but it does take two to tango. Good luck with this.