Terrebonne Parish, LA Environmental Rules: Flood Elevation Requirements (2026)

Sec. 9-1 defines freeboard as 'an additional amount of height above the base flood elevation used as a factor of safety' when setting how high a structure's lowest floor must be elevated or floodproofed, and fixes the minimum at one foot, noting the state building code can push it higher depending on the type of structure. Sec. 9-57(1) turns that safety margin into a hard construction standard for homes: any new residential structure, or one undergoing a substantial improvement, must have its lowest floor, including a basement, elevated to or above the minimum elevation set by the effective building code, the 2021 IBC as amended.

A registered professional engineer, architect, or land surveyor has to certify to the floodplain administrator that the standard is met. Nonresidential buildings get an alternative under Sec. 9-57(2): they can either meet the same elevation or be floodproofed below it, watertight and structurally rated to resist hydrostatic and hydrodynamic loads, with an engineer's certification of the specific floodproofed elevation kept on file. Sec. 9-57(9) layers on a parish sewer standard where it is stricter: under Chapter 23's building sewer rule, new-construction floor tops must sit at least eighteen inches above the highest crown of the adjacent street so plumbing fixtures keep working.

Enclosed areas below the lowest floor used only for parking, building access, or storage need flood vents, at least two openings totaling one square inch of net area per square foot of enclosed space, with the lowest opening no higher than one foot above grade.