Building permits in St. Clair County, Illinois
Find the right authority before you build. St. Clair County permitting follows Illinois law — here is exactly who issues the permit and where to start.
County + cities (mixed)
St. Clair County Building & Zoning Department (unincorporated areas); municipalities issue their own permits
The St. Clair County Building & Zoning Department issues building permits and enforces the adopted building code for the unincorporated areas of the county. Properties inside an incorporated municipality (e.g., Belleville, O’Fallon, East St. Louis) are permitted by that municipality, not the county.
Open the official permit portal →
A 9-1-1-assigned address and an energy-code compliance certificate are required before a county building permit is issued.
Check a home project's permit in St. Clair County, Illinois
Select a project to see its Illinois permit rule. Whether the county or your city issues it depends on incorporation status — see the authority note above.
Illinois
Exact permit fees are set by the local building department. WikEst shows the published or code-based range where one exists, linked to its official source — verify the final amount at the source before budgeting.
🏠 Accessory Dwelling Unit (ADU) permit fee in Illinois
Permit requiredCase by casecity authority
Permit fee range
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.
Typical timeline
Varies
Setback
—
Exempt if
Not size-exempt
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.
Official sources: City of Chicago — Guide to Building Permits (2019 Chicago Building Code) · ICC — Illinois Codes (no statewide code; local adoption)
Representative cities for Illinois: Chicago, Springfield.
All 20 project fee ranges in Illinois
Official-source ranges where published; “By local jurisdiction” means no flat fee is published and the amount is set case by case.
| Project | Permit? | Authority | Fee range | Go / no-go |
|---|---|---|---|---|
| 🏠 Accessory Dwelling Unit (ADU) | yes | 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 |
| 🪵 Deck / Porch | yes | city | Chicago fees via online calculator; other municipalities set their own. | allowed |
| 🧱 Fence / Wall | conditional | city | Set by local jurisdiction | allowed |
| 🛖 Shed / Outbuilding | conditional | city | Set by local jurisdiction | allowed |
| 🪜 Basement Finish | yes | city | Municipal building permit fee; varies with scope. | allowed |
| 🚗 Garage / Carport | yes | city | Municipal building permit fee. | allowed |
| ☀️ Rooftop Solar PV | yes | city | Electrical/structural permit fee set by municipality. | allowed |
| 🌡️ HVAC Replacement | yes | city | Mechanical permit fee set by municipality. | allowed |
| 🍳 Kitchen Remodel | yes | city | Building permit fee; trade permits billed separately. | allowed |
| 🛁 Bathroom Remodel | yes | city | Building permit fee; trade permits billed separately. | allowed |
| 🏗️ Room Addition | yes | city | Building permit fee based on valuation; zoning and plan review apply. | allowed |
| 🪟 Window / Door Replacement | conditional | city | Set by local jurisdiction | allowed |
| 🏘️ Roof Replacement | yes | city | Roof-covering permit fee set by municipality. | allowed |
| 🅿️ Driveway / Parking Pad | conditional | city | Set by local jurisdiction | allowed |
| 🏊 Swimming Pool / Spa | yes | city | Building permit fee; barrier fencing required by code. | allowed |
| 🧱 Retaining Wall | conditional | city | Set by local jurisdiction | allowed |
| 💥 Demolition / Teardown | yes | city | Demolition permit fee set by the municipality; verify locally. | allowed |
| 🚰 Septic System | yes | county | Private sewage permit fees set by the local health department; verify locally. | allowed |
| 🔌 EV Charger | conditional | city | Electrical permit fee set by the municipality; verify locally. | allowed |
| ⚡ Standby Generator | yes | city | Electrical (and often mechanical/gas) permit fee set by the municipality; verify locally. | allowed |
Permit cheat-sheet (Illinois rules)
| 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. |
| 💥 Demolition / Teardown | Permit required | city | Demolition permit fee set by the municipality; verify locally. | — | Generally allowed | A full teardown or major strip-out requires a demolition (building) permit from the municipality. Illinois has no statewide building code, so Chicago and other cities issue the permit under their locally adopted code; unincorporated areas are permitted by the county. Demolition permits often require utility disconnects and, for older homes, asbestos/lead clearance. |
| 🚰 Septic System | Permit required | county | Private sewage permit fees set by the local health department; verify locally. | — | Generally allowed | New or replacement onsite wastewater (private sewage / septic) systems require a permit from the local health department under the Illinois Private Sewage Disposal Code (77 Ill. Adm. Code 905). Engineered design and a site/perc evaluation are required; the local health department is the permitting authority. |
| 🔌 EV Charger | Conditional | city | Electrical permit fee set by the municipality; verify locally. | — | Generally allowed | A home EV charging station needs an electrical permit (dedicated 240V circuit and wall unit) issued by the municipality. Illinois has no single statewide EV-permitting fast-track, so review time varies by city (Chicago processes through its permits program). Work must meet the NEC. |
| ⚡ Standby Generator | Permit required | city | Electrical (and often mechanical/gas) permit fee set by the municipality; verify locally. | — | Generally allowed | A permanently installed standby generator with a transfer switch and fuel (gas/propane) line requires electrical and often mechanical/gas permits, plus inspection. Setback, noise, and carbon-monoxide rules may apply, and HOAs may restrict installation. Verify with the municipality (e.g., Chicago DOB). |
Frequently asked questions
Who issues building permits in St. Clair County, Illinois?
St. Clair County Building & Zoning Department (unincorporated areas); municipalities issue their own permits is the permitting authority for St. Clair County. Permitting is split — cities issue for incorporated areas, the county for unincorporated areas. Start at the official portal linked above.
Do I go to the county or my city for a building permit in St. Clair County?
Permitting is split — cities issue for incorporated areas, the county for unincorporated areas.
What home projects need a permit in St. Clair County?
The same project types shown in the cheat-sheet above (ADU, deck, fence, shed, solar, and more) — rules follow Illinois state law. Whether the county or your city issues it depends on your property's incorporation status.
How do I apply for a permit in St. Clair County?
Use the official permit portal linked above. Most offices accept online submissions; have your plans, site information, and contractor details ready before applying.