(a) Generally. In all areas of special flood hazard where base flood elevation data have been provided, as set forth in section 90-31 or 90-47, the standards in this section are required.

(b) Residential construction. new construction or substantial improvement of any residential structure shall have a first floor (i.e., lowest living area) elevation which is a minimum of 12 inches above the crown of any street (measured at centerline) which is contiguous to the site. Should solid foundation perimeter walls be used to elevate a building, openings sufficient to facilitate the unimpeded movements of floodwaters shall be provided in accordance with standards of sections 90-62 through 90-65.

(c) Nonresidential construction. new construction or substantial improvement of any commercial, industrial or nonresidential structure shall have a first floor elevation which is a minimum of 12 inches above the crown of any street (measured at centerline) contiguous to the site. Buildings located in all A-zones may be floodproofed in lieu of being elevated provided that all areas of the building below the required elevation are water-tight with walls substantially impermeable to the passage of water, and use structural components having the capability of resisting hydrostatic and hydrodynamic loads and the effect of buoyancy. A registered professional engineer or architect shall certify that the standards of this subsection are satisfied. Such certification shall be provided to the official set forth in section 90-49.

(d) Elevated buildings. new construction or substantial improvements of elevated buildings that include fully enclosed areas formed by the foundation and other exterior walls below the base flood elevation shall be designed to preclude finished living space and designed to allow for the entry and exit of floodwaters to automatically equalize hydrostatic flood forces on exterior walls as follows: