Residential permit rules in Illinois

Representative cities: Chicago, Springfield. Covers 16 common home projects.

Verify locally. Illinois has no single statewide building code — most municipalities adopt the IRC locally while Chicago enforces its own 2019 Chicago Building Code. Permit rules differ significantly between Chicago and the rest of the state; verify with your specific city (e.g., Chicago DOB or Springfield). Rules below are state/city-level guidance drawn from official sources — always confirm with the issuing building department before starting work. See the county permit authorities to find the right office.

Project	Permit?	Authority	Typical fee	Timeline	Go / No-Go	Key notes
🏠 Accessory Dwelling Unit (ADU)	Permit required	city	No flat statewide fee; Chicago calculates fees from construction type, occupancy, square footage, and scope via its online calculator. Other municipalities set their own fees.	—	Case by case	Illinois has no statewide building code; most municipalities use the IRC while Chicago enforces the 2019 Chicago Building Code. ADUs require a building permit plus local zoning approval — Chicago and other cities regulate ADUs through zoning. Verify with your municipality.
🪵 Deck / Porch	Permit required	city	Chicago fees via online calculator; other municipalities set their own.	—	Generally allowed	Decks and porches require a permit (Chicago requires permits for decks/porches). Chicago offers an Express Permit for eligible deck work; most other IL towns follow IRC R105.
🧱 Fence / Wall	Conditional	city	—	—	Generally allowed	Chicago requires a permit for fences (handled via the Express Permit Program). Other Illinois municipalities often exempt fences at or below 6 ft. Verify locally.
🛖 Shed / Outbuilding	Conditional	city	—	—	Generally allowed	Larger sheds and any shed with utilities require a permit. Confirm the threshold with your local building department. Exempt: Under ~120 sq ft typically exempt under the IRC; varies by municipality.
🪜 Basement Finish	Permit required	city	Municipal building permit fee; varies with scope.	—	Generally allowed	Finishing a basement into habitable space requires permits for egress, framing, electrical, plumbing, and mechanical work. Sleeping rooms need code-compliant egress.
🚗 Garage / Carport	Permit required	city	Municipal building permit fee.	—	Generally allowed	A new garage requires a permit. Chicago’s Easy/Express Permit covers private (detached frame) garages; elsewhere a standard building permit applies.
☀️ Rooftop Solar PV	Permit required	city	Electrical/structural permit fee set by municipality.	—	Generally allowed	Rooftop solar PV requires an electrical and structural permit. Chicago’s Express Permit covers small-scale residential solar PV; other municipalities issue a solar/electrical permit.
🌡️ HVAC Replacement	Permit required	city	Mechanical permit fee set by municipality.	—	Generally allowed	Furnace, AC, or heat-pump replacement requires a mechanical (HVAC) permit and inspection. Chicago requires a city-licensed mechanical contractor.
🍳 Kitchen Remodel	Permit required	city	Building permit fee; trade permits billed separately.	—	Generally allowed	A permit is required when relocating plumbing/electrical, moving walls, or changing fixtures. Cosmetic-only work may be exempt.
🛁 Bathroom Remodel	Permit required	city	Building permit fee; trade permits billed separately.	—	Generally allowed	A permit is required when relocating plumbing/electrical, moving walls, or changing fixtures. Cosmetic-only updates may be exempt.
🏗️ Room Addition	Permit required	city	Building permit fee based on valuation; zoning and plan review apply.	—	Generally allowed	Room additions change the footprint and require a full building permit and zoning approval. Chicago uses the 2019 Chicago Building Code for plan review.
🪟 Window / Door Replacement	Conditional	city	—	—	Generally allowed	Swapping windows or exterior doors in the same opening is usually permitted via an expedited process; enlarging openings requires a full permit.
🏘️ Roof Replacement	Permit required	city	Roof-covering permit fee set by municipality.	—	Generally allowed	Re-roofing is covered by Chicago’s Express Permit; elsewhere a roofing permit is required. Minor repairs may be exempt.
🅿️ Driveway / Parking Pad	Conditional	city	—	—	Generally allowed	A permit may be required where the driveway connects to the street/right-of-way or triggers an excavation/erosion permit. Verify locally.
🏊 Swimming Pool / Spa	Permit required	city	Building permit fee; barrier fencing required by code.	—	Generally allowed	Pools require a permit and barrier. Chicago processes pools via its Express/specialty permit programs; other municipalities issue a standard permit.
🧱 Retaining Wall	Conditional	city	—	—	Generally allowed	Height and whether the wall supports a surcharge (driveway, structure, or slope above) determine the permit threshold. Verify with your municipality.

State-wide sources: ICC — Illinois Codes (no statewide code; local adoption) · Illinois Capital Development Board — Building Codes · City of Chicago — Guide to Building Permits (2019 Chicago Building Code) · City of Chicago Dept. of Buildings — Permits