ADU Regulations — Chicago, IL

Governed by Sec. 17-2-1701. Last verified June 2, 2026.

All Areas

Requirement	Value	Conditions / Exceptions	Source
Allowed Zones	RS, RT, RM, and certain other residential districts	—	Sec. 17-2-1701
Height Limit Feet	Complies with zoning district height limits; if detached, max 2 stories	—	Sec. 17-2-1703(e)
Max Size Sqft	1000 sq ft or 50% of principal dwelling floor area, whichever is less	—	Sec. 17-2-1703(a)
Number Per Lot	1	—	Sec. 17-2-1703(b)
Owner Occupancy Required	Yes - owner must occupy either the principal dwelling or the ADU	—	Sec. 17-2-1703(c)
Parking Spaces Required	1 off-street space per ADU	Exempt if within 1/2 mile of a rapid transit station or in a residential permit parking zone	Sec. 17-2-1703(d)
Setback Requirement	Must comply with principal building setbacks of the zoning district	Exception: Setbacks may be reduced for interior ADUs (within existing building)	Sec. 17-2-1703(f)

Rear Yard

Requirement	Value	Conditions / Exceptions	Source
Location Restriction	Detached ADUs must be located in the rear yard	Exception: Existing building conversions allowed anywhere on lot	Sec. 17-2-1703(g)

Official Code Language (8 sections)

Accessory dwelling units are permitted in RS, RT, RM, and certain other residential districts, as listed in Section 17-2-1701.

— Sec. 17-2-1701

The accessory dwelling unit must comply with the height limits of the underlying zoning district; if detached, it is limited to a maximum of two stories, under Section 17-2-1703(e).

— Sec. 17-2-1703(e)

The maximum floor area of an accessory dwelling unit shall not exceed 1,000 square feet or 50% of the principal dwelling's floor area, whichever is less, per Section 17-2-1703(a).

— Sec. 17-2-1703(a)

No more than one accessory dwelling unit is permitted on a single lot, as specified in Section 17-2-1703(b).

— Sec. 17-2-1703(b)

The owner of the property must occupy either the principal dwelling or the accessory dwelling unit, per Section 17-2-1703(c).

— Sec. 17-2-1703(c)

One off-street parking space is required for each accessory dwelling unit, as per Section 17-2-1703(d).

— Sec. 17-2-1703(d)

The accessory dwelling unit must adhere to the same setback requirements as the principal building in the zoning district, according to Section 17-2-1703(f).

— Sec. 17-2-1703(f)

Detached accessory dwelling units must be located in the rear yard of the lot, per Section 17-2-1703(g).

— Sec. 17-2-1703(g)

Permit Requirements

When required: Any construction or conversion of an ADU requires a building permit
Fee: — Fees vary based on project scope; see Department of Buildings fee schedule
Where to apply: Chicago Department of Buildings

Documents needed:

Building permit application
Site plan
Floor plans
Elevations
Proof of ownership
Parking plan if applicable

Verified June 2, 2026

Permit Application Checklist

Track your progress applying for a ADU Regulations permit in Chicago. Your progress is saved automatically.

0 of 8 items complete

Frequently Asked Questions

Can I build an ADU that is bigger than my main house?

- No, the maximum size is the smaller of 1,000 sq ft or 50% of your principal dwelling's floor area. - For example, if your house is 1,500 sq ft, your ADU can be at most 750 sq ft.

Am I required to live in the ADU or on the property?

- Yes, you must occupy either the principal dwelling or the ADU. - This rule ensures the property remains owner-occupied.

Do I need to provide additional parking for an ADU?

- Yes, one off-street parking space is required for each ADU. - The space must be off the street, such as a driveway or garage.

Where on my lot can I put a detached ADU?

- Detached ADUs must be located in the rear yard. - They cannot be placed in the front or side yards.

Sources

Data last verified: June 2, 2026

See how this works nationally: ADU Rules by State

This is an informational summary, not legal advice. Verify current requirements with Chicago Planning Department .

Found an error? Report a correction to help keep this information accurate.