Williamson County, Illinois Building Permit Guide

No county building, zoning or planning department appears on the Williamson County website. Its Cities and Villages page links official pages for Carterville, Creal Springs, Herrin, Hurst, Johnson City and Marion, and also lists Bush, Cambria, Colp, Crainville, Energy, Freeman Spur, Pittsburg, Spillertown, Stonefront and Whiteash. By the Census Bureau’s 2025 estimates the largest municipalities are Marion city (17148), Herrin city (12268), Carterville city (5839) and Johnston City city (3313).

This guide covers the building offices of Marion, Herrin and Carterville, the county Highway Department and the Bi-County Health Department. The county page links only a Facebook page for Johnston City, so no official Johnston City building details are given; contact the city directly.

What requires a permit in Williamson County?

Marion requires residential building permits for any new construction such as storage buildings, garages and decks, and excavation permits when a curb, sidewalk or street will be cut. Herrin requires building permits for anything over 10 sq ft under roof. Private sewage permits in Williamson County come from the Franklin-Williamson Bi-County Health Department.

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

Who handles permitting in Williamson County?

Local rules in Marion, Herrin and Carterville

Marion

Besides building and excavation permits, Marion requires a Dirt Hauling Permit for any dirt hauled into the city and a Commercial Occupancy Permit for a new business, change of ownership or relocation.

Herrin

Permits are needed for anything over 10 sq ft under roof; the certificate-of-occupancy inspection is booked at (618) 942-6004.

Carterville

The owner or contractor must stake out the project before applying, and commercial plans need an architect’s stamp. Property must be annexed before water or sewer taps can be permitted.

Williamson County permit costs and fees

• Herrin: 10 cents per sq ft under roof; certificate-of-occupancy inspection $25.00.
• Carterville: $.10 per square foot of construction under roof.
• County driveway culverts: a 12-inch x 24-foot culvert installed by the Highway Department is $460.08 plus a $225.00 fee, $685.08 total. Credit cards are accepted for culvert installation and road permits.
• Private sewage permit (Bi-County Health): $150 per permit.

How to get a permit in Williamson County

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

Inspections in Williamson County

Carterville requires four inspections: site, footings, pre-sheetrock and final. Herrin’s certificate-of-occupancy inspection costs $25.00 and is booked at (618) 942-6004, weekdays 8:30 am to 2:00 pm. Bi-County Health needs 48 hours’ notice before sewage system construction starts.

Official Williamson County permitting resources

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

• Williamson County cities and villages
• Williamson County Highway Department
• Bi-County Health private sewage procedures
• Marion Building and Code Services
• Herrin code enforcement
• Carterville building permits

Frequently asked questions

Does Williamson County issue building permits?

No county building department appears on the county website; Marion, Herrin and Carterville issue their own building permits.

What does a septic permit cost in Williamson County?

$150 per permit from the Franklin-Williamson Bi-County Health Department, with 48 hours’ notice before construction.

Does a small shed need a permit in Herrin?

Herrin requires a building permit for anything over 10 sq ft under roof, at 10 cents per sq ft.

Simplify Williamson 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 Williamson County permitting. Requirements, fees, and procedures change; confirm details with the permitting authority before relying on them.