Knox County, TN Environmental Rules: Flood Elevation Requirements (2026)

Sec. 34-52 of the Knox County flood damage prevention chapter sets the county's freeboard standard above the National Flood Insurance Program's base flood elevation (BFE). For residential construction, where BFE data is available, new construction or substantial improvement of any residential building or manufactured home must have its utilities, including electrical, heating, ductwork, ventilating, plumbing, and air conditioning equipment, and its lowest floor, including any basement, elevated no lower than one foot above the base flood elevation, a one-foot freeboard above the federal minimum. Nonresidential buildings face the same one-foot-above-BFE standard but may floodproof instead of elevate, provided a registered professional engineer or architect certifies the design meets accepted watertight construction standards and files that certification with the Engineering Department under Sec.

34-32(2). Where a structure sits in an unnumbered A zone, meaning base flood elevation data has not been established and no alternative data is available, the Engineering Department instead requires the lowest floor to be elevated or floodproofed to at least three feet above the highest adjacent grade. Solid perimeter foundation walls used to elevate a structure must include openings sized to equalize hydrostatic flood forces on both sides of the exterior walls. Applicants apply for a development permit through the Engineering Department, which records the as-built lowest-floor elevation certification after construction; failure to submit that certification, or failure to correct a deficiency the department identifies, is grounds for a stop-work order under Sec.

34-32. Variances from these standards go to the county board of adjustments and enforcement under Sec. 34-34, which may not lower flood levels within a designated floodway.