Mercer County, Illinois Roofing Permit Regulations and County Ordinances for Unincorporated Areas
Mercer County Building & Safety Divisions
In Mercer County, Illinois, building and zoning matters are handled by the Mercer County Zoning Office. This office is responsible for receiving and reviewing applications for building permits. Because this office operates on a part-time basis, it is recommended that you allow up to 48 hours for a response to inquiries made via phone or email.
Rules for Properties in Unincorporated Areas
The Mercer County Zoning Ordinance applies to the unincorporated areas of the county. If you are planning a construction project, you must submit an application for a building permit to the Zoning Office. The current fee structure for building permits includes a $25.00 application fee plus $5.00 per $1,000.00 of the cost of improvements.
When submitting an application, you are required to provide a site plan (drawing) that includes the dimensions of the lot or tract of land, the exact location of all proposed buildings and structures, and other information as requested by the Zoning Officer. Please note that while the county regulates building and zoning, Illinois state law provides exemptions for buildings or structures used for agricultural purposes, though these may still be required to conform to specific building or setback lines.
It is important to verify if your specific project requires a permit, as requirements can vary based on the scope of work. Additionally, while the county manages zoning, you should always ensure that any contractor hired for roofing work holds a valid license issued by the Illinois Department of Financial and Professional Regulation, as required by state law.
Resources to Learn More
Note: The following state-wide building codes and regulations apply universally to all jurisdictions within Illinois, including Mercer County.
Illinois Roofing Legislation, Codes, and Guidelines
State-Level Building Codes and Legislation for Roofing in Illinois
As of January 1, 2025, Illinois has implemented a statewide baseline building code requirement pursuant to Public Act 103-0510, which amended the Capital Development Board Act. This legislation mandates that all municipalities and counties in Illinois must adopt and enforce building codes that meet or exceed the minimum structural requirements of the International Code Council (ICC) standards, specifically the International Building Code (IBC) and the International Residential Code (IRC). Prior to this, Illinois did not have a unified statewide building code, and regulations were determined entirely at the local municipal or county level.
While the state now requires a baseline, local jurisdictions retain the authority to adopt their own specific editions (such as the 2018, 2021, or 2024 editions) and implement local amendments, provided those amendments do not reduce the structural requirements below the state-mandated baseline. Consequently, specific roofing requirements—such as those for ice and water shields, ventilation, and shingle layering—can still vary significantly between different cities, villages, and counties. Property owners and contractors must consult their local Authority Having Jurisdiction (AHJ) to confirm the specific code edition and local amendments applicable to their project.
Primary State Agency
The Illinois Capital Development Board (CDB) is the primary state agency responsible for the administration of the state's building code framework. Under the Capital Development Board Act (20 ILCS 3105), the CDB is tasked with identifying and publishing local building codes and ensuring that municipalities and counties comply with the requirement to report their adopted codes and amendments to the state.
Resources to Learn More