Fence requirements vary by local building codes. One can call their local building department for their specific fencing regulations. Most pools are required to be surrounded by a fence. A few areas with lot sizes of three acres or more are exempt. Generally swimming pool enclosure fencing must be a minimum of 4'-0" and a maximum of 6'-0" tall. If it is chain link, the mesh size may not be larger than 1.5". For wooden fences, typically board on board is acceptable but the specific construction detail may have to be approved. No larger than a 4” space can be found either beneath, or anywhere in the fence body including abutting and adjoining fences.