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.
Yes, ADUs are allowed in Chicago, IL. California state law ensures by-right approval.
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, ADUs are permitted by right under state law, making them one of the most accessible ways to add housing on your property. 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: 1000 sq ft. Attached ADU max size: 700 sqft or no more than the existing unit square footage, whichever is less. Setbacks: 2 ft side, 2 ft rear. Owner-occupancy: Owner-occupancy required. Property owner must reside in either the principal unit or the ADU. This requirement is enforced through annual affidavit to Chicago DPD..
Costs & Fees
ADU permits in Chicago: Total estimated permit cost: $1,500–$6,500 total permit fees. Contact the Chicago Department of Buildings for current fee schedule.
Timeline
Chicago DPD building permit for ADU: typically 3-6 months for plan review. ADU Express program in development. Construction 4-12 months.
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 Chicago Department of Buildings at https://www.chicago.gov/city/en/depts/bldgs/provdrs/permits.html. 3. Hire a licensed contractor familiar with IL ADU requirements.
Chicago Department of Buildings
Phone: (312) 744-5000
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 webapps1.chicago.gov/zoneinfo/ — 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