Accessory building or use customarily incidental to any of the above uses, including, but not limited to, a storage garage on a lot occupied by a multiple-family dwelling, rooming house or boardinghouse, hospital or institution, private garages, guest houses, swimming pools, home barbecue grills, customary church bulletin boards or identification signs not exceeding thirty (30) square feet in area for permitted public and semipublic uses, and accessory off-street parking and loading spaces.