Kendall County, IL Environmental Rules: Flood Elevation Requirements (2026)

Kendall County's floodplain ordinance (Kendall County Code Chapter 16, Article II, Subdivision IV) sets the base flood elevation (BFE) from the FEMA County-wide Flood Insurance Study of Kendall County dated January 8, 2014, covering panels such as 17093C0005G through 17093C0225H (Sec. 16-139). The county then adds a mandatory margin: the flood protection elevation (FPE) is the BFE plus two feet of freeboard, or, outside mapped plan limits, the higher of the water table or the 100-year design water surface plus two feet (Sec. 16-52). Under Sec.

16-140(c), every new building and every substantial improvement (work equal to or exceeding 50 percent of the structure's market value, figured cumulatively over a ten-year period) in the regulatory floodplain must have its lowest floor, including any basement, raised to the FPE. Nonresidential buildings may substitute dry-floodproofing up to the FPE instead of elevating, but only if a registered professional engineer certifies the design is watertight and self-operating without outside power. Attached garages get a lighter standard: elevation to at least one-half foot above the BFE rather than the full FPE.

Builders may reach the FPE by permanent fill placed in six-inch compacted lifts extending twenty feet beyond the foundation, structural elevation on piers or walls with flood vents sized at one square inch per square foot of enclosed area, or an engineered crawlspace no taller than four feet measured to the top of the foundation wall. Manufactured homes must be anchored under the Illinois Mobile Home Tie-Down Act. The Floodplain Administrator reviews every plan and elevation certificate before issuing the stormwater permit required for floodplain development.