Adair County, IA Environmental Rules: Flood Elevation Requirements (2026)

Section III of Ordinance No. 37 turns the one-foot freeboard rule into building standards inside the special flood hazard areas, which are Zone A on the Flood Insurance Rate Map dated April 5, 2017. For residential buildings, the lowest floor, including basement, must be elevated a minimum of one foot above the 100-year flood level. Construction must sit on compacted fill that is no lower than 1.0 ft. above the 100-year flood level at any point and extends at that elevation at least 18 feet beyond the limits of any structure on it. Where existing topography, street grades or other factors preclude fill, the Board of Supervisors can favorably consider alternate methods such as piers, which must support the structure and withstand the forces and hazards of flooding. New residential structures also need access passable by wheeled vehicles during the 100-year flood.

For non-residential buildings the lowest floor, including basement, must be elevated a minimum of one foot above the 100-year flood level, or the building and its utility and sanitary systems must be floodproofed to that level. Floodproofing requires certification by a professional engineer registered in Iowa that the methods withstand flood depths, pressures, velocities, impact and uplift forces and that the structure is watertight below the 100-year flood level. The Administrator keeps a record of the floodproofed elevation in relation to North American Vertical Datum 1988.

The same one-foot margin applies to factory-built homes, which need a permanent foundation, and to water supply and wastewater treatment facilities other than on-site systems. Storage of flammable, explosive or injurious materials is prohibited unless elevated a minimum of one foot above the 100-year flood level. Levees and flood walls need protection from a 100-year flood with a minimum of 3 ft. of design freeboard and Department of Natural Resources approval.

Detached garages, sheds and similar structures incidental to a residential use are exempt from the base flood elevation requirements if they do not exceed 600 sq. ft., are used solely for purposes such as vehicle parking and limited storage, are never used for human habitation, and are firmly anchored. Section III(K)(2) warns that the exemption risks higher flood insurance premiums for the structure and its contents. The ordinance defines the base flood as the flood with a one percent chance of being equaled or exceeded in any given year.