On this page 6
§ 02
When a permit is required
Permit triggers and exempt work for Mercer County
New construction, additions, and alterations exceeding $1,000 in value or changing exterior dimensions.
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)
- Exempt Routine maintenance (painting, wallpapering)
- Exempt Re-roofing (if no structural change)
- Exempt Insulation
- Exempt Alterations costing less than $1,000 that do not change exterior dimensions
- Exempt Structures used strictly for agricultural purposes (may require 'No Fee' zoning certificate)
Required documents
- Application form
- Site plan
- Contractor list
- Health Department approval (if no public sewer)
- Building code
- 2021 International Building Code (IBC) and 2021 International Residential Code (IRC) per 2025 state mandate.
- Permit validity
- Typically 1 year from issuance.
- Owner-builder
- Permitted for primary residences; must comply with all codes.
§ 03
Application process
Typical processing: Allow up to 48 hours for initial response; full processing typically 5-10 business days.
- 01 Submit a completed Building Permit Application including parcel number and township.
- 02 Provide a Site Plan (Drawing A) showing property lines, existing/proposed structures, and setbacks.
- 03 Submit Health Department approval for well/septic if applicable (309-582-3759).
- 04 Review by Zoning Officer (Matt Lower).
- 05 Payment of fees upon approval.
- 06 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 ↗
§ 04
Fee schedule
Mercer County building permit fees
Fee type
Amount
01
Minimum permit fee
$25.00
02
Plan check fee
Included in base fee for standard residential
03
Permit fee formula
$5.00 per $1,000.00 of estimated improvement cost
04
Reinspection fee
Not explicitly listed; double fees apply for work started without a permit
05
Penalty (no permit)
Double fees for work started without a permit
Checks payable to Mercer County Treasurer.
Fees change periodically. Confirm at the official fee schedule ↗ before budgeting.
§ 05
Required inspections
Scheduling and sequence
How to schedule
- Contact Zoning Officer at 309-525-3799 (phone)
- Inspection hours
- By appointment (Part-time office)
Typical sequence: Footing/Foundation, Rough-in (Electric/Plumbing/Framing), Final.
§ 06
Frequently asked
Common questions about unincorporated Mercer County permits
01 Do I need a building permit in unincorporated Mercer County, IL? ▸
New construction, additions, and alterations exceeding $1,000 in value or changing exterior dimensions.
02 How much does a building permit cost in unincorporated Mercer County, IL? ▸
Building permit fees in unincorporated Mercer County, IL are set by the local building department and vary by project type and valuation. The minimum permit fee is $25.00. Fees are calculated as: $5.00 per $1,000.00 of estimated improvement cost. Plan check fee: Included in base fee for standard residential.
03 How do I apply for a building permit in unincorporated Mercer County, IL? ▸
To apply for a building permit in unincorporated Mercer County, IL, follow these steps: 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.
04 How long does it take to get a building permit in unincorporated Mercer County, IL? ▸
Building permit processing times in unincorporated Mercer County, IL typically run Allow up to 48 hours for initial response; full processing typically 5-10 business days.. Timelines can vary based on project complexity and current department workload.
05 What work is exempt from building permits in unincorporated Mercer County, IL? ▸
Not all construction work requires a permit in unincorporated Mercer County, IL. The following work is generally exempt: 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). When in doubt, confirm with the local building department before starting work.
06 How do I schedule a building inspection in unincorporated Mercer County, IL? ▸
Once your permit is issued and work reaches an inspection milestone, you can schedule a building inspection in unincorporated Mercer County, IL via: Contact Zoning Officer at 309-525-3799.
last verified April 2026
source Mercer County Zoning Office ↗
entry id permits/illinois/mercer/unincorporated
Educational reference. Permit rules and fees change — confirm current requirements directly with Mercer County Zoning Office before applying. Jaspector is not legal advice.