A good fence of wood, iron, wood and iron rods or wire, stone, or well set thorn, 41/2 feet high or 4 feet high and having a ditch within 2 feet of it, shall be deemed a lawful fence in New Castle and Kent Counties, and in Sussex County 4 feet shall be the height of lawful fences. Barbed wire shall not be used for division fences except by the mutual consent of the owners of the properties divided by such fences. No fence of any kind which is composed in whole or in part of, or to which there is or has been added, barbed wire, razor wire or any barbed wire type of fencing material shall be permitted in any residential district without prior approval of the county or municipal zoning board or its board of adjustment, unless the property being enclosed by such fence is being used for farming or educational purposes.