There shall not be more than one principal structure and not more than two accessory structures, including a private garage, on each lot zoned residential which is composed of 14,400 square feet or less. Additional accessory structures may be constructed and maintained if the lot exceeds 14,400 square feet in size, but only one additional accessory structure may be constructed and maintained for each 14,400 square feet of lot space. In no case, however, shall there be more than five accessory buildings on any one lot zoned residential.