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

The McHenry County Stormwater Management Ordinance's Building Protection Standards for Flood Hazard Areas (Section C, item 11) cover any new building, building addition, or substantial improvement located within a mapped floodplain, plus any new building or addition in a flood prone area built after December 1, 2014 that adds more than 600 square feet of enclosed area below the BFE. 5 foot of freeboard. ' Builders pick an acceptable protection measure from Table 6: construction on permanent fill, elevation on crawl space, stilts, piles or walls, dry floodproofing, or wet floodproofing, though dry floodproofing is not an option for a residential building sitting inside the mapped floodplain.

Fill must follow FEMA Technical Bulletin 10-01 guidance, and every building component below the FPE must use flood damage-resistant materials. Manufactured homes, recreational vehicles and travel trailers parked more than 180 consecutive days must also be raised to or above the FPE and tied down per the Illinois Mobile Home Tie-Down Act rules. Every covered building needs a FEMA elevation certificate or floodproofing certificate before the County Enforcement Officer signs off, though small accessory buildings may submit alternate documentation the Enforcement Officer finds acceptable. The requirement stays in force on a mapped floodplain parcel until a Letter of Map Change (LOMC) is obtained from FEMA.