Maximum building height: 35 feet, subject to the provisions of § 348-5.12; provided, however, that the height of the building or portion thereof may exceed the maximum as otherwise permitted, provided that the front, rear and side yard requirements set forth within the zone shall be increased by five feet for each foot by which the height of the building or part thereof exceeds the permitted maximum height, and further provided that in no case shall any proposed building or part thereof exceed 40 feet in height and three usable floor areas counted vertically at any point in the building above the grade level as determined by the average grade elevation of the corners of the building.