Some counties welcome barndominiums, but metro and suburban areas may restrict them.
No statewide building code. State enforces a plumbing code and Life Safety Code (fire regulations) statewide. Local jurisdictions adopt their own building codes. Chicago has its own unique building code.
Primary Code
IBC / IRC (locally adopted)
Code Version
Varies by jurisdiction (2015–2021 IBC)
Adoption Level
Local Only
Statewide Enforcement
No
Cook County and collar counties have full permitting. Many rural downstate counties have minimal requirements.
Residential
Required
Commercial
Required
Agricultural
Not Required
Size threshold: structures under 200 sq ft may be exempt.
Farm buildings used for agricultural purposes are generally exempt from building permits in many Illinois jurisdictions. Illinois has strong agricultural protections.
Small structures under 200 sq ft typically exempt in most jurisdictions.
Southern Illinois (Carbondale area) is in a higher seismic zone near the New Madrid fault. Moderate snow loads statewide. Wind loads increase near Lake Michigan.
Wind Load
90–115 mph
moderate zone
Snow Load
15–35 psf
Seismic
A–D
Category
Flood
FEMA Regulated
Energy Code
IECC (locally adopted)
Version
Varies (2012–2021 IECC)
No statewide energy code. Municipalities adopt their own energy codes.
License Type
No state license required
Illinois does not require a state-level contractor license. Chicago and many municipalities require local contractor licenses.
Front
25–40 ft
Side
5–15 ft
Rear
15–30 ft
Setbacks vary widely by jurisdiction.
Frost depth of 42 inches in most of the state. Basements are very common in residential construction.
Popular in rural areas. Permits vary by jurisdiction.
Agricultural exemptions widely available. Illinois is a major farming state.
Growing in popularity in central and southern Illinois. Acceptance varies by county.
Standard permit requirements in cities. Rural areas more flexible.
Full IBC compliance required in jurisdictions with code enforcement.
HOAs are common in suburban developments around Chicago. Downstate rural areas generally have no HOA restrictions.
Extensive flood zones along the Mississippi, Illinois, and Ohio rivers. FEMA flood zone maps apply.
Verify the information above directly from these official sources. Regulations change — always confirm with your local building department before starting construction.
Disclaimer: This guide is for informational purposes only and does not constitute legal or professional advice. Building codes, permit requirements, and zoning regulations change frequently. Always verify current requirements with your local building department, planning office, or a licensed professional before starting construction. Homestead Steel Structures & Design is not a legal authority on building codes or zoning regulations. Last updated February 2026.
