Nassau County, FL Hurricane Preparedness: Flood Elevation (2026)

1 of the Florida Building Code, Residential to set the county's minimum floor elevations for homes in flood hazard areas. Outside Coastal A Zones, the lowest floor must sit at or above the base flood elevation plus 1 foot or the design flood elevation, whichever number is higher, and the same plus-1-foot standard applies to below-grade basement floors. Inside a Coastal A Zone, the same base-flood-elevation-plus-1-foot standard governs the lowest horizontal structural member rather than just the floor. In AO Zones, where FEMA maps show only a shallow-flooding depth number rather than a base flood elevation, the lowest floor, including any basement, must sit at least as high above the highest adjacent grade as that depth number plus 1 foot, or at least 3 feet if the map does not list a depth number at all; in A-Zones with no base flood elevation shown, the code sets a flat 36-inch minimum above the highest adjacent grade.

1, also adopted under § 7-8, tells the building official what to do when a site's design flood elevation is not already established or a floodway is not designated: the official can require the applicant to obtain flood data from a federal, state or other source, have a registered design professional determine the elevation using accepted hydrologic and hydraulic practice, or, if no other data exists and the official finds it reasonable, simply set the base flood elevation at 3 feet above the highest adjacent grade.

1 folds this into ordinary permit review by requiring every site plan to show the proposed finished floor elevation, confirming that where a lot sits in a special flood hazard area, the lowest floor must be at least 1 foot above FEMA's 100-year flood elevation.