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Overview
LOCAL ADOPTION with state minimums. No mandatory statewide residential building code. Individual municipalities and counties choose whether to adopt codes and which editions. Chicago uses entirely separate Chicago Building Code (NOT ICC). Illinois Energy Conservation Code (IECC-based) applies statewide. Illinois Roofing Industry Licensing Act requires statewide roofing contractor license (IDFPR). Home-rule municipalities (pop >25,000) have significant autonomy. Many rural/unincorporated areas have limited or no building code requirements. Climate Zones 4A (south) and 5A (north/central). Ice barrier required statewide. Frost depth 30-48 inches.
Code Snapshot
Current editions in effect
Building Code
CBC Current (separate system)
Current (separate system)
Code
IAC Current
Current
Building Code
IBC Local Adoption
Local Adoption
Code
ICC Local Adoption
Local Adoption
Code
ICCPC Local Adoption
Local Adoption
Building Code
IEBC Local Adoption
Local Adoption
Effective Date: January 1, 2020
Verified: Mar 2026
Jurisdiction Complexity
Illinois is a MODERATE complexity state
Illinois applies state-level code amendments to ICC base codes, with some variation across local jurisdictions.
SimpleModerateComplex
Wind-Borne Debris
Varies by locality →Key Rules & Requirements
Critical regulations for Illinois restoration work
Illinois has adopted the Energy Efficient Building Act requiring IECC compliance, but enforcement is primarily at the local level. Most jurisdictions have adopted IECC 2018 or 2021, but verify local adoption.
Important: The Illinois Energy Efficient Building Act (20 ILCS 3125) establishes minimum energy efficiency standards based on IECC. However, Illinois does NOT have a statewide residential building code - code adoption is at the discretion of local municipalities and counties. Most urban and suburban areas have adopted the IECC (typically 2018 or 2021 editions). Rural areas may have limited or no enforcement. Chicago has its own energy code provisions within the Chicago Building Code that may differ from IECC. The Illinois Capital Development Board (CDB) oversees state-funded buildings. Private construction is locally regulated. For insurance restoration projects, verify which IECC edition is adopted locally and whether REScheck compliance is required. Third-party energy verification (HERS rating, REScheck, ComCheck) may be required depending on jurisdiction.
Illinois requires smoke detectors per the Smoke Detector Act (425 ILCS 60) and CO detectors per Lilly Law (430 ILCS 135). Both are state statutes applying statewide regardless of local building code adoption.
Important: Illinois Smoke Detector Act (425 ILCS 60) requires smoke detectors on each level, in each sleeping room, and outside sleeping areas in all residential units. Illinois Carbon Monoxide Alarm Detector Act (430 ILCS 135, the Lilly Law) requires CO alarms within 15 feet of every sleeping room in dwellings with fuel-burning appliances or attached garages. These are state statutes — they apply in ALL Illinois jurisdictions regardless of whether the municipality has adopted a building code. Interconnected and hardwired required in new construction.
Illinois ground snow loads range from 20 psf in the south to 30 psf in the north per ASCE 7. All roof structures must be designed for local ground snow load where IRC is adopted.
Important: Per ASCE 7 as referenced by the IRC, Illinois ground snow loads range from 20 psf in southern Illinois to 25 psf in central Illinois and 30 psf in northern Illinois (Chicago metro). Roof structures must be designed for the local ground snow load per IRC R301.6 where adopted. While Illinois snow loads are moderate compared to northern tier states, they are significant enough to require proper structural design, particularly for wide-span roofs and areas subject to drift loading.
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Code Administration
Administering Agency
Illinois Building Commission
Code Portal
cdb.illinois.govState Statute
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Jurisdictions
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ZIP Codes
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Special Zones
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Codes
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Climate Zones
Applicable Codes
Key Codes for Restoration Work
Primary codes for residential restoration projects in Illinois
| Code Type | Current Edition | Effective Date | Base Code | Status | Actions |
|---|---|---|---|---|---|
Chicago Building Code (City of Chicago ONLY) Commercial & Multi-Family | CBC Current (separate system) | Jan 1, 2020 | IBC 2021 w/ amendments | Current | View Details |
International Building Code Commercial & Multi-Family | IBC Local Adoption | Jan 1, 2024 | IBC 2021 w/ amendments | Current | View Details |
International Existing Building Code Commercial & Multi-Family | IEBC Local Adoption | Jan 1, 2024 | IBC 2021 w/ amendments | Current | View Details |
International Energy Conservation Code 2021 Energy Efficiency Standards | IECC 2021 | Jan 1, 2022 | IECC 2021 w/ amendments | Current | View Details |
International Energy Conservation Code (Commercial) Energy Efficiency Standards | IECC-C 2021 | Jan 1, 2022 | IECC 2021 w/ amendments | Current | View Details |
International Energy Conservation Code (Residential) Single-Family & Townhomes | IECC-R 2021 | Jan 1, 2022 | IRC 2021 w/ amendments | Current | View Details |
Illinois Energy Conservation Code Energy Efficiency Standards | IL-ECC 2018 | Jul 1, 2019 | IECC 2018 w/ amendments | Current | View Details |
International Residential Code Single-Family & Townhomes | IRC Local Adoption | Jan 1, 2024 | IRC 2021 w/ amendments | Current | View Details |
National Electrical Code 2020 (NFPA 70) Building Requirements | NEC 2020 | Jan 1, 2020 | NEC 2018 w/ amendments | Current | View Details |
Chicago Building Code (City of Chicago ONLY)
Commercial & Multi-Family
CBC Current (separate system)Details
International Building Code
Commercial & Multi-Family
IBC Local AdoptionDetails
International Existing Building Code
Commercial & Multi-Family
IEBC Local AdoptionDetails
International Energy Conservation Code 2021
Energy Efficiency Standards
IECC 2021Details
International Energy Conservation Code (Commercial)
Energy Efficiency Standards
IECC-C 2021Details
International Energy Conservation Code (Residential)
Single-Family & Townhomes
IECC-R 2021Details
Illinois Energy Conservation Code
Energy Efficiency Standards
IL-ECC 2018Details
International Residential Code
Single-Family & Townhomes
IRC Local AdoptionDetails
National Electrical Code 2020 (NFPA 70)
Building Requirements
NEC 2020Details
Effective dates reflect when each code edition was formally adopted by the state. Dates may differ across code types when amendments are adopted in separate rulemaking cycles. Base codes reference the ICC model code edition that serves as the foundation for the state's adopted version. Verify current applicability with your local Authority Having Jurisdiction (AHJ).
Get a jurisdiction-specific code packet
Enter a Illinois ZIP code for exact applicable codes, special zones, and a compliance checklist.
Special Zones
Special Zones
Radon
Illinois EPA Radon Zone 3 - Low Priority
EPA-designated Radon Zone 3 counties (lowest priority). Predicted average indoor radon screening levels less than 2 pCi/L. Covers southernmost Illinois including Alexander, Pulaski, Massac, Pope, Hardin, Johnson, Union counties. Radon testing still recommended as any home can have elevated radon.
Requirements: Testing recommended despite lower risk; RRNC optional but beneficial; 4 pCi/L action level still applies
View sourceFlood & Coastal
Illinois Floodplain Management
Local floodplain ordinance compliance required for construction in FEMA-designated flood zones. Illinois has extensive river valley flooding (Mississippi, Illinois, Ohio, Wabash, Fox, Des Plaines). Local communities administer floodplain regulations.
Requirements: Lowest floor elevated to or above Base Flood Elevation (BFE).; Freeboard often required (1-2 feet above BFE).; Flood-resistant materials below BFE.; Flood openings in foundation walls.; NFIP compliance required for federally-backed mortgages.; Elevation Certificate typically required.; Substantial improvement threshold: 50% of market value.; Contact local floodplain administrator before any construction in mapped flood zones.
View sourceHistoric Preservation
Illinois Historic Districts (State/Federal)
State and federal historic districts in Illinois. Illinois Historic Preservation Agency (IHPA) serves as State Historic Preservation Office (SHPO). Review required for projects with state or federal involvement in historic properties. Local historic preservation commissions may have additional requirements.
Requirements: Local Historic Preservation Commission review may be required.; Illinois SHPO review for state/federal involvement.; Certificate of Appropriateness may be required for exterior changes.; Replacement materials should match original appearance.; Federal Historic Preservation Tax Credit available for qualifying work (20%).; Illinois Historic Preservation Tax Credit available (25%).; Secretary of Interior Standards apply for tax credit projects.; Contact IHPA at (217) 782-4836.
View sourceWind & Hurricane
IL Tornado-Prone Region
State within or adjacent to the tornado corridor. NOAA SPC data confirms significant tornado frequency. Enhanced structural requirements apply per IRC R301.2.1.2.
Requirements: Enhanced roof-to-wall connections per IRC R802.11; Continuous load path from roof to foundation; Safe room construction per ICC 500/FEMA P-361 recommended; Garage door bracing for wind resistance
Snow & Ice
Illinois Statewide Ice Barrier Zone
Ice barrier required statewide for ALL roofing projects in Illinois per IRC R905.1.2 (where IRC is adopted). All of Illinois is in Climate Zones 4A or 5A, which require ice barrier underlayment. Must extend minimum 24 inches inside exterior wall line. Required at eaves, valleys, and around penetrations.
Requirements: Self-adhering polymer-modified bitumen sheet required. Extend from eave edge to at least 24 inches inside exterior wall line. Required at all eaves, valleys, and penetrations. Northern IL (Zone 5A) has higher ice dam frequency due to Lake Michigan influence. Document installation with photos for inspection. Chicago has separate requirements - verify with Chicago DOB.
View sourceClimate & Energy
Climate Zones
IECC Climate Zones in Illinois
4AMixed-Humid
Mixed-Humid
moist
5ACool-Humid
Zone 5A - Cool Humid
moist
Energy Code Requirements
IECC 2021 - Residential Insulation Minimums
| Component | Zone 4A | Zone 5A |
|---|---|---|
Ceiling Attic | 49.0 | 49.0 |
Wood Frame Wall | 20.0 | 20.0 |
Mass Wall | 13.0 | 17.0 |
Floor | 19.0 | 30.0 |
Basement Wall | 10.0 | 15.0 |
Slab Perimeter | 10.0 | 10.0 |
Crawl Space Wall | 10.0 | 15.0 |
Window | 0.320 | 0.300 |
Skylight | 0.550 | 0.550 |
Door | 0.350 | 0.350 |
Legend:
Ceiling Attic
Wood Frame Wall
Mass Wall
Floor
Basement Wall
Slab Perimeter
Crawl Space Wall
Window
Skylight
Door
NR = Not Required
Fenestration Requirements
U-Factor (Max)
0.320
SHGC (Max)
0.40
Ice Barrier
Required
R-Value Requirements (Zone 4A - Most Common)
R-49.0
Ceiling
Attic/Roof
R-20.0
Walls
Wood Frame
R-19.0
Floor
Over Uncond.
R-10.0
Basement
Wall
R-10.0
Slab
Perimeter
NR
Crawlspace
Not Required
Counties
Illinois Counties
102 jurisdictions with code information
Adams County
FIPS: 17001
Standard
17 ZIP codesView
Alexander County
FIPS: 17003
Standard
8 ZIP codesView
Bond County
FIPS: 17005
Standard
8 ZIP codesView
Boone County
FIPS: 17007
Standard
5 ZIP codesView
Brown County
FIPS: 17009
Standard
3 ZIP codesView
Bureau County
FIPS: 17011
Standard
24 ZIP codesView
Calhoun County
FIPS: 17013
Standard
8 ZIP codesView
Carroll County
FIPS: 17015
Standard
7 ZIP codesView
Cass County
FIPS: 17017
Standard
6 ZIP codesView
Showing 9 of 102 jurisdictions.
Inspection Process
Inspection Process
Standard permit inspection sequence for Illinois residential projects
1
Foundation Inspection
After excavation, forms, and reinforcement in place
If applicable
2
Rough Framing Inspection
After framing complete, before insulation or covering
3
Roof Sheathing Inspection
After roof deck complete, before ice barrier or underlayment
Before roofing
4
Ice Barrier / Dry-In Inspection
After ice barrier and underlayment installed, before final roofing material
5
Insulation / Energy Inspection
After insulation installed, before drywall or covering
Energy code compliance
6
Window/Door Installation Inspection
After installation, before exterior trim/siding covers flanges
Final Inspection
After all work complete
CO Issued
Important Notes
24-Hour Notice: Schedule inspections at least 24 hours in advance.
Permit Card: Must be posted and visible from street.
Re-Inspection Fees
- First re-inspection
- Often free
- Second re-inspection
- $50-100
- Additional re-inspections
- Varies
* Fees vary by jurisdiction
Contacts & Resources
Illinois Capital Development Board (CDB)
Springfield
Illinois Department of Financial and Professional Regulation (IDFPR)
Springfield
Illinois Historic Preservation Agency (IHPA)
Springfield
Office of the State Fire Marshal (OSFM)
State Building Code Authority
Illinois Environmental Protection Agency (IEPA)
Springfield
Chicago Department of Buildings (DOB)
Chicago
Contractor Licensing
Contractor licensing in Illinois is managed at the state level. Contact the state licensing board or visit your local building department for specific requirements and license verification.
Data last verified: February 2026 · Always verify requirements with the local building department.