Can I Build ADU in Chicago, IL? (2026)
Find out if you can build a adu in Chicago, IL. Rules, permit requirements, costs, and next steps.
Whether ADUs are allowed in Chicago, IL has not been confirmed — contact the local building department or see the official source before proceeding.
An Accessory Dwelling Unit (ADU) is a secondary housing unit on a residential lot — also called a granny flat, in-law suite, or backyard cottage. In Chicago, IL, ADU regulations are in flux — state law and local ordinances interact to determine what is permitted. ADUs can be detached, attached to the main home, or created by converting an existing garage or accessory structure.
ADU Rules in Chicago
ADU Rules in Chicago: Detached ADU max size: size varies by zoning — see official source. Attached ADU max size: size varies by zoning — see official source. Setback requirements are not confirmed — see official source. Owner-occupancy: Owner-occupancy applies only where the principal building on the zoning lot adding a conversion unit or coach house is a detached house — that detached house must be owner-occupied at the time of pre-certification..
Costs & Fees
ADU permits in Chicago: Contact the local building department for current fee schedule.
Next Steps
Next steps for building an ADU in Chicago: 1. Review full ADU rules including size limits, setbacks, and parking. 2. Apply for an ADU permit through the local building department. 3. Hire a licensed contractor familiar with IL ADU requirements.
Chicago Department of Buildings
Phone: (312) 744-3449 · Verified July 6, 2026 · Source
Website: https://www.chicago.gov/city/en/depts/bldgs.html
Online Permits: https://www.chicago.gov/city/en/depts/bldgs/provdrs/permits.html
Frequently Asked Questions
Can I build an ADU in Chicago?
Yes. Chicago's ADU Ordinance, expanded citywide in July 2022, allows both attached ADUs (basement or attic conversions) and detached coach houses (rear-yard ADUs typically built over a garage). Owner-occupancy is required — you must live in either the primary unit or the ADU. No replacement parking is required. A building permit from the Chicago Department of Buildings is required.
What is a coach house in Chicago, and is it the same as an ADU?
Yes. In Chicago, a coach house is the traditional term for a detached ADU — typically a 1- or 2-story structure built over a rear garage, accessed from the alley. Chicago's ADU Ordinance specifically authorizes coach houses up to 1,000 sqft and 22 ft tall. They are built in the rear yard, behind the principal building. Chicago has a rich history of coach houses from the late 19th and early 20th centuries.
How do I find the zoning of my Chicago property?
Use the City of Chicago Zoning Map at gisapps.chicago.gov/ZoningMapWeb/ — enter your address to find zone designation, applicable district standards, and special overlay zones. You can also check the Chicago Zoning Ordinance (Title 17) at codelibrary.amlegal.com.
Are short-term rentals allowed in Chicago?
Yes, with a license. The Chicago Shared Housing Ordinance (effective 2016) requires a Vacation Rental License or Shared Housing Host Registration ($125/year). Properties in buildings where the condo or co-op association has voted to ban short-term rentals are prohibited. Chicago collects a 4.5% Shared Housing Surcharge plus state hotel tax.
What are the setbacks for a standard Chicago bungalow lot?
In RS-3 (the most common single-family zone for Chicago bungalows), setbacks are: 15 ft front, 2 ft side (minimum — many have 2 ft on one side and 0 on the other with a shared driveway), and 30 ft rear. Chicago's standard lot is 25 ft wide by 125 ft deep. The rear yard is typically used for detached garages accessed from the alley.
Source: Chicago Department of Buildings — Building Regulations. Last verified April 3, 2026. View source