Illinois

Illinois adopted a statewide building code effective January 1, 2025, requiring all jurisdictions to enforce at least the 2024 IBC. Previously, Illinois was one of the few states without a mandatory statewide code — local jurisdictions could choose whether to adopt building codes. Southern Illinois is in the New Madrid Seismic Zone (SDC C-D). Central and northern Illinois are in lower seismic categories (SDC A-B). Illinois is in Tornado Alley — the state averages 54 tornadoes per year. Chicago has its own building code (Chicago Building Code) which is more stringent than the state minimum. Cook County and collar counties (DuPage, Kane, Lake, McHenry, Will) have robust enforcement programs.