Birmingham, AL Environmental Rules: Flood Elevation Requirements (2026)

b of the zoning ordinance sets the specific elevation standards that apply once base flood elevation data exists for a site. For residential construction, the rule leaves no discretion: new construction or substantial improvement of any residential structure, or manufactured home, must have the lowest floor, including basement, elevated no lower than one foot above the base flood elevation. That one-foot cushion above the FEMA base flood elevation is the city's freeboard requirement. Nonresidential buildings get an alternative compliance path: the lowest floor can be elevated the same one foot, or the building can be floodproofed so that below the required elevation the structure is watertight with walls substantially impermeable to the passage of water and structural components capable of resisting hydrostatic and hydrodynamic loads, with a registered professional engineer or architect certifying that the floodproofing meets the standard.

Elevated buildings that enclose space below the required floor for parking or storage must include 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, so floodwater can flow through automatically. Manufactured homes in an existing park face the same one-foot lowest-floor elevation requirement, plus a chassis support standard of piers at least 36 inches above grade. The applicant must submit the proposed lowest-floor elevation with the permit application and, after the floor is framed, certify the as-built elevation to the Department of Planning, Engineering and Permits before further work can proceed.