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Do I Need a Permit to Build a ADU or Tiny Home on my Property in Illinois
Do counties in Illinois require building permits to build an in-law suite or accessory dwelling unit on your property?
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In most cases counties in Illinois do require building permits to construct an in-law suite or accessory dwelling unit (ADU) on your property. Here are some key points about ADU/in-law suite permitting requirements in Illinois counties:
County Jurisdiction: Regulation of ADUs typically falls under county jurisdiction outside of incorporated municipal areas. Counties set their own permit rules.
Permits Required: The vast majority of Illinois counties require permits for the construction of any new dwelling unit, including attached or detached ADUs/in-law suites.
Zoning Compliance: Even if state law allows ADUs, counties review permit applications to ensure the proposed unit meets local zoning regulations like setbacks, lot coverage, unit size, etc.
Building Codes: Permits allow the county to inspect the ADU construction for compliance with applicable building and fire codes.
Utility Connections: Separate utility connections for the ADU often require permitting as well.
Minimal Exemptions: While a few counties may allow very small ADUs under a certain square footage to be built permit-free, these exemptions are quite limited.
Some examples of Illinois counties clearly requiring ADU/in-law suite permits include Cook, DuPage, Lake, Kane, Will and McHenry Counties surrounding Chicago. But the permit process details can vary somewhat by county.
Attempting to construct an ADU without proper county permitting can result in fines, stop work orders, or even having to remove the unpermitted construction. So it is highly advisable to go through the required county permitting channels for any new in-law suite or ADU in Illinois. A few minor exceptions aside, permits are generally mandatory.
