Onslow County, NC Environmental Rules: Flood Elevation Requirements (2026)

Sec. 7-5 defines the regulatory flood protection elevation as the elevation to which a structure's reference level must be protected in a special flood hazard area: where FEMA has determined a base flood elevation (BFE), the regulatory elevation is the BFE plus two feet of freeboard; where no BFE has been established, it is at least two feet above the highest adjacent grade. That standard is not academic; Sec. 7-97(1) requires that new construction or substantial improvement of any residential structure, including manufactured homes, have its reference level, including any basement, elevated no lower than the regulatory flood protection elevation.

Nonresidential buildings get the same elevation standard under Sec. 7-97(2), though they may floodproof to that elevation instead if a registered engineer or architect certifies the design. The two feet of freeboard exists precisely to buffer against the engineering uncertainty and watershed development changes noted in the Sec. 7-5 definition. Compliance is checked through the certification pipeline in Sec. 7-67(3): an elevation certificate is required before construction starts, another within seven days after the reference level is established, and a final as-built elevation certificate before the county issues a certificate of compliance or occupancy.

The floodplain administrator reviews each certificate and can require corrections before construction proceeds. This freeboard requirement applies to development within Onslow County's mapped special flood hazard areas in the unincorporated county; it does not govern Camp Lejeune's own flood construction standards on federal land.