St. Clair County, Illinois Building Permit Guide

The St. Clair County Building & Zoning Department handles zoning for the unincorporated areas of the county, issues building, electrical and occupancy permits and does building and occupancy inspections. Of the county’s 250,708 residents (latest Census estimate), 49,602 live in the unincorporated balance; the most populous cities are Belleville (40,237) and O’Fallon (32,656).

This guide covers the county department, the towns it inspects under contract, and the City of Belleville. County pages list different office hours and phone numbers, so this guide gives the department’s sidebar number; call to confirm hours. County commercial permit fees were not checked.

Who handles permitting in St. Clair County?

The county also provides building inspections under contract for East Carondelet, Fayetteville, Freeburg, Lenzburg, Marissa, Millstadt, New Athens and St. Libory.

What comes before a county building permit

Before a building permit, the property needs an address from the 9-1-1 Coordinating Office, a completed Application for Certificate of Zoning Compliance with its $30 fee, and a Builder’s Statement of Understanding, Acceptance and Agreement.

Since March 1, 2025, every detached accessory building needs one set of interior plans and a recorded affidavit, prepared by the Zoning Office, before the permit is issued. Commercial and industrial permits need plans sealed by an Illinois-licensed architect on every sheet.

Building or repairing a private sewage system needs a permit from the St. Clair County Health Department first; the system must be installed by a state- and county-licensed contractor or the homeowner.

Illinois leaves building codes to local government, but since 1 January 2025 any local code must regulate structural design at least as strictly as baseline editions of the International Building, Existing Building and Residential Codes, and where no code was adopted the statute sets minimums for commercial buildings and new homes (Public Act 103-0510). Illinois codes and the statewide baseline

St. Clair County permit costs and fees

• Application fee: $30 on every county building permit; zoning compliance letters are also $30.00 (since January 2020).
• Single family residence: $500 for 2,500 sq ft and under, $700 for 2,501 sq ft and larger.
• Residential remodels: $220 for $10,000 cost; $250 for $10,001 - $50,000.
• Other: decks and carports $125; garages and pole buildings $175; in-ground pools $200; demolition $100.
• Plan review, due at drop-off: residential $75.00, commercial $100.00.
• Stormwater Management and Erosion Control Permit Fee: 34% of the building permit fee, when required.
• Private sewage: Health Department application fee $300.00.

How to get a building permit in St. Clair County

A building permit carries a validity period set by the county or city that issues it; confirm the expiry on phased or delayed work before it passes. Permit validity in Illinois

Inspections in St. Clair County

Call 24 hours before you need an inspection with the permit number, address and owner’s name. The permit must be posted and the property marked with its address. A failed inspection brings a $75 re-inspection fee, paid before the next inspection. The department also handles flood zone determinations and zoning appeals.

Building permits in Belleville

In Belleville, permits come from the city’s Health, Housing & Building Department, and applications can be emailed to building@belleville.net. The city’s page lists the 2006 International Building and Residential Codes and the 2014 National Electric Code; that is what the city lists, so confirm the edition with the department. Belleville requires a residential Certificate of Occupancy inspection before a new resident may legally occupy a home.

Official St. Clair County permitting resources

These are the primary sources behind this guide. Codes, fee schedules and procedures change — confirm the position for your filing date.

• St. Clair County Building & Zoning
• St. Clair County building permits
• St. Clair County Health Department private sewage
• St. Clair County Highway Department
• Belleville Health, Housing & Building

Frequently asked questions

Which towns does St. Clair County inspect for?

East Carondelet, Fayetteville, Freeburg, Lenzburg, Marissa, Millstadt, New Athens and St. Libory, under contract.

What does a new house permit cost in unincorporated St. Clair County?

$500 for 2,500 sq ft and under or $700 for 2,501 sq ft and larger, plus the $30 application fee.

Does a new resident in Belleville need an inspection?

Yes. Belleville requires a residential Certificate of Occupancy inspection before a new resident may legally occupy a home.

Simplify St. Clair County permitting with Alliance Permitting

• Confirm whether the county or a city or village has the parcel, and which office to file with
• Line up the health, highway and floodplain approvals that come before the building permit
• File with the right office and keep inspections on schedule

Alliance Permitting is a permit documentation and submission company in Illinois. We prepare your paperwork, file it correctly and coordinate with the permitting authority through issuance. We are not a contractor and we do not perform licensed plan review or inspections; that work stays with your licensed team and the jurisdiction.

This guide is provided by Alliance Permitting for general information about St. Clair County permitting. Requirements, fees, and procedures change; confirm details with the permitting authority before relying on them.