Generally, in all Zoning Districts, your fence may not be more than 4 feet high in the front of your property or, in the case of a corner lot, more than 4 feet high on any side facing the street. In addition, the first 20 feet (from the front yard) on the side property may not be more than 4 feet high, or in the case of a corner lot, the first 10 feet along the side of the rear property from the street may not be more than 4 feet high. It may not be more than 6 feet high on the sides or rear. (Measured from the lowest adjacent natural grade.) Exceptions are possible for areas outside of the Coastal Zone.
Building permits are required for fences constructed above retaining walls. You do not need a building permit if the fence meets zoning requirements and is wooden or cyclone.
For more detailed information, please read our pamphlet How to Apply for a Permit to Build a Fence or refer to Section 6412 of the San Mateo County Zoning Regulations.