Boone County, IN Environmental Rules: Flood Elevation Requirements (2026)

Boone County Code § 152.36(B) requires new construction or substantial improvement of any residential structure, including a manufactured home, in a special flood hazard area (SFHA) to have its lowest floor, including any basement, at or above the Flood Protection Grade (FPG), defined elsewhere in the chapter as two feet above the base flood elevation. Section 152.36(C) applies the same two-foot freeboard standard to commercial, industrial and other non-residential structures, but gives owners the option to floodproof to the FPG instead of elevating, provided a registered professional engineer or architect certifies under § 152.36(C)(1) that the structure and its utilities are watertight and can resist the regulatory flood's velocity, duration and hydrostatic pressure.

Structures elevated on solid foundation perimeter walls must include flood openings meeting § 152.36(D)'s minimum criteria: at least two openings totaling one square inch of net area per square foot of enclosed area, positioned no more than one foot above grade. No development can begin in the SFHA without a floodplain development permit under § 152.12, and § 152.13 bars any structure from being located, extended, converted or structurally altered there without full compliance, backed by the § 152.36(A) rule that structures over 400 square feet, additions worth 50% or more of the structure's value, and substantial repairs to storm-damaged buildings all trigger the FPG protection requirement. The Boone County Area Plan Commission's Floodplain Administrator handles permit review and elevation verification under §§ 152.26 and 152.27.