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St. Clair County, Illinois · St. Louis metro

Metal buildings in O’Fallon, IL.

We supply shops, garages, farm buildings, commercial buildings and more across O’Fallon and eastern St. Clair County. Our work reaches from O’Fallon and Shiloh to the farm ground around Lebanon and Summerfield, and anywhere else you’re building. The city moved to the 2021 codes on January 1, 2026.

Building code

2021 IBC

Zoning permit from

101 sq ft

Building permit from

200 sq ft

Codes updated

Jan. 2026

These are City of O’Fallon rules. Unincorporated St. Clair County permits through its own office.

Call 314-536-8688
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What people build around O’Fallon

O’Fallon has grown east along I-64. Past the edge of town, the county is grain ground and acreage.

Garages on city lots

City lots set the footprint. We work from your survey before settling on a size.

Acreage shops

Tubular steel is usually the answer for an unfinished shop under sixty feet wide.

Machine sheds

Equipment storage goes up on the farm ground toward Lebanon and Summerfield. Red iron takes over past eighty feet or for combine doors.

Barndominium shells

Steel truss is the fit here. Drywall attaches to the frame, so there’s no second wall to build.

Permitted commercial work along the corridors often suits cold-formed steel, with a finished eave standard. See what a steel building costs.

Permitting metal buildings in O’Fallon and St. Clair County

Each Illinois city and county adopts its own building code. O’Fallon updated its codes at the start of 2026.

Inside O’Fallon

  • The city has enforced the 2021 IBC and IRC since January 1, 2026.
  • Accessory buildings from 101 to 199 sq ft need a zoning permit.
  • At 200 sq ft and up, they need a building permit and a zoning permit.
  • Call the Building and Inspections Division at (618) 624-4500.

Unincorporated St. Clair County

  • The county permits and zones land outside city limits.
  • Detached accessory buildings need interior plans and a recorded Zoning Office affidavit before the permit is issued.
  • Building & Zoning is at 10 Public Square in Belleville.

Farm buildings in Illinois

  • State law keeps counties from regulating or requiring permits for farm buildings.
  • Farming has to be the main activity on the land.
  • Setback lines still apply.

The code changed this year. O’Fallon moved to the 2021 codes on January 1, 2026. Drawings and quotes prepared before then may assume the older edition, and the edition sets the wind and snow loads a building is engineered for. We engineer to the code in force at your address.

We also serve Shiloh, Lebanon, Summerfield, Mascoutah and Caseyville. See Belleville, the St. Louis metro or all of Illinois.

Start with a conversation

Let’s talk about your O’Fallon project.

Tell us what you’re planning and where you’re building. We’ll help you work out the next steps.

  1. Tell us what and whereSend us the size, how you’ll use the building and the address.
  2. We check the siteWe confirm who permits the address and which code and loads apply.
  3. You get a clear recommendationWe recommend the frame that fits and price it against the alternatives.
Book a consultation

Or call
314-536-8688