Porches, balconies, decks, stoops, landings. Unenclosed porches, balconies, decks, stoops or landings may project not more than five feet beyond the front, side and rear walls of a building into the minimum front, side or rear yard setback for the district and shall not be closer than five feet from any lot line. "Unenclosed" shall mean no side enclosure, other than railings, that is more than 18 inches in height, exclusive of screens. Any two-story or enclosed porch shall be considered a part of the building in the determination of the required setback.