The building code in force in Illinois now.

Capital Development Board Act baseline (PA 103-0510), from Jan 1, 2025: where no local code exists, IBC and IEBC (1/1/25 edition, Chapters 11, 13, 29 excluded; current or preceding edition) and, for residential, IRC (1/1/24 edition); local codes must be at least as strict

CDB's page lists the IBC/IEBC and IRC baselines plus state energy, accessibility, plumbing and fire rules (including NFPA 101) applying everywhere. State-funded and CDB buildings follow the Illinois Stretch Energy Code. Municipalities report adopted codes to CDB 30 days before effect.

Source: primary document

Municipal and county building officials (local AHJs); Capital Development Board administers the statewide baseline, the 30-day code-adoption reporting requirement, the Illinois Energy Conservation Code (2024 IECC-based, effective Nov 30, 2025) and the Illinois Accessibility Code

Statewide layer. County and city amendments sit on top; confirm the local office for the address.

In force

In force; CDB links 2026 Stretch Energy Code proposals but the page does not say whether adopted

• Cook County's Building and Zoning Department is the building official for unincorporated areas and the Forest Preserves; every incorporated city, including Chicago, runs its own building department.
• Chicago requires periodic exterior-wall inspections for buildings 80 feet or taller, with cycle length and short-form vs. critical-exam status set by wall material category rather than one fixed age.
• A Chicago building-owners association reported that City Council approved on June 17, 2026 a Department of Buildings ordinance aligning the Chicago Construction Codes with the 2024 model codes (secondary copy, not the primary text); the effective date could not be confirmed on the primary page. Confirm which code edition applies to a permit with the Department of Buildings.