County Building Permits

Mercer County Building Permit Guide (Unincorporated Area)

How to apply for a building permit in unincorporated Mercer County, Illinois. Permit authority, application steps, fees, and inspection requirements.

Illinois Updated March 2026

Permit Authority

Responsible for all permitting and zoning in areas outside incorporated city or village limits.

Department
Mercer County Zoning Office
Address
100 SE 3rd St, Aledo, IL 61231
Phone
309-525-3799 (Zoning Officer Cell) / 309-582-5353 (Main Office)
Website
https://www.mercercountyil.org/government/zoning

Online Permit Portal

Open Mercer County Zoning Office

Platform: Manual/PDF-based • Account required: No • Submission: In-person only

Application Process

  1. Submit a completed Building Permit Application including parcel number and township.
  2. Provide a Site Plan (Drawing A) showing property lines, existing/proposed structures, and setbacks.
  3. Submit Health Department approval for well/septic if applicable (309-582-3759).
  4. Review by Zoning Officer (Matt Lower).
  5. Payment of fees upon approval.
  6. Permit issuance.

Typical processing time: Allow up to 48 hours for initial response; full processing typically 5-10 business days.

Source: Mercer County Zoning Office

General Requirements

New construction, additions, and alterations exceeding $1,000 in value or changing exterior dimensions.

Required Documents

  • Application form
  • Site plan
  • Contractor list
  • Health Department approval (if no public sewer)
Permit validity
Typically 1 year from issuance.
Building code
2021 International Building Code (IBC) and 2021 International Residential Code (IRC) per 2025 state mandate.
Owner-builder
Permitted for primary residences; must comply with all codes.
Contractor requirements
No general contractor license required. State license required for Roofing, Plumbing, and Electrical.

Fees

Minimum permit fee
$25.00
Plan check fee
Included in base fee for standard residential
Permit fee formula
$5.00 per $1,000.00 of estimated improvement cost
Reinspection fee
Not explicitly listed; double fees apply for work started without a permit
Penalty (no permit)
Double fees for work started without a permit
Payment note
Checks payable to Mercer County Treasurer.

Fees change. Verify current amounts at the official fee schedule.

Work That Does NOT Require a Permit

  • Routine maintenance (painting, wallpapering)
  • Re-roofing (if no structural change)
  • Insulation
  • Alterations costing less than $1,000 that do not change exterior dimensions
  • Structures used strictly for agricultural purposes (may require 'No Fee' zoning certificate)

Inspections

How to Schedule

  • Contact Zoning Officer at 309-525-3799 (phone)
Inspection hours
By appointment (Part-time office)

Typical inspection sequence: Footing/Foundation, Rough-in (Electric/Plumbing/Framing), Final.

Additional Resources

Information on this page was last verified: March 2026. Permit rules and fees change — confirm current requirements directly with the Mercer County Zoning Office before applying.

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Important: This page is an educational resource provided by jaspector.com. It is not legal advice, and it does not substitute for official guidance from the permit authority listed above. Permit requirements, fees, and processes change frequently. Always verify current requirements directly with the issuing department before beginning any construction project. Use of this page does not create an attorney-client relationship. Jaspector assumes no liability for any outcomes arising from reliance on this information.
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