Chicago, IL Accessory Structures: ADU Rules (2026)
ADU rules in Chicago, IL, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- Max height
- 22 feet, including rooftop features
- Units allowed
- One dwelling unit per coach house
- Side open space
- At least 3 feet unobstructed to the sky
- Rear separation
- 15 feet (reducible to 10 ft by adjustment)
- B/C district placement
- Rear 30 feet of lot depth only
- Accessory parking
- Not required for the coach house
Summary
Chicago's Zoning Ordinance caps coach houses, the classic garage-apartment ADU, at 22 feet in building height, including rooftop features, and limits each one to a single dwelling unit. Section 17-9-0201-F also requires 3 feet of open side yard, a 15-foot rear separation from the principal house, and rear-30-foot placement in B or C districts.
17-9-0201-F Coach Houses. ... 2. In B or C zoning districts, a coach house may only be established in the rear 30 feet of the lot depth. ... 5. Coach houses may not exceed 22 feet in building height. 6. Rooftop features may not exceed 22 feet in overall height above grade. 7. At least three feet of open space that is unobstructed and unoccupied from its lowest level to the sky must be provided between the coach house and at least one side property line for the entire length of the building wall, except when a side property line abuts an alley or street. 8. A minimum separation of 15 feet must be provided between the rear wall of the principal building and the front wall of the coach house; provided, however, that on zoning lots which measure less than 125 feet between the front property line and the rear property line, such separation distance may be reduced to no less than 10 feet, when approved as an administrative adjustment pursuant to Section 17-13-1003-PP. 9. Only one dwelling unit is permitted per coach house.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: 2026 S-74: Current through Council Journal of June 17, 2026).
Full Breakdown
Section 17-9-0201-F sets the bulk standards that every Chicago coach house must meet regardless of which ADU-Allowed RS Area it sits in. In B or C zoning districts, a coach house may only be established in the rear 30 feet of the lot depth. Height is capped at 22 feet for the coach house itself and separately at 22 feet for rooftop features measured above grade. At least 3 feet of open, unobstructed space open to the sky must run along at least one side property line for the entire length of the building wall, unless that side property line abuts an alley or street.
Between the rear wall of the principal building and the front wall of the coach house, a minimum 15-foot separation applies; on zoning lots under 125 feet deep, that gap can shrink to no less than 10 feet, but only with an administrative adjustment approved under Section 17-13-1003-PP. Only one dwelling unit is permitted per coach house, and it cannot be built before the principal building on the lot exists. Coach houses are also exempted from the minimum lot area, open space, and floor area ratio provisions that would otherwise apply under Sections 17-2-0303-A, 17-2-0307, 17-2-0308, 17-2-0304-A, and related district sections, though they can't cut into open space that already serves the principal building.
Accessory parking to serve the coach house is not required at all. For RS-zoned lots, Section 17-9-0201-F(1) further requires compliance with the separate Additional Dwelling Unit-Allowed RS Area rules of Section 17-7-0570 before the Department of Buildings can issue a building permit.
Violations & Fines
A coach house that doesn't meet these bulk standards, oversized height, insufficient side or rear separation, or a second dwelling unit crammed into one structure, simply can't get a building permit; Section 17-9-0201-F(1) blocks permit issuance on RS-designated lots that don't comply with the underlying ADU rules, and the Department of Buildings reviews plans against the height, setback, and separation limits before sign-off. Reducing the 15-foot rear separation below 15 feet requires an administrative adjustment under Section 17-13-1003-PP first, building without it leaves the structure non-compliant and unpermittable.
Frequently Asked Questions
How tall can a Chicago coach house be?
Can I put two apartments in one coach house?
How far must a coach house sit from the main house?
Do I need extra parking spaces for a coach house?
Sources & Official References
Other rules in Chicago
How Chicago compares: Easiest Cities to Build an ADU·Compare Chicago to another location·View the Illinois accessory structures overview
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ADU Rules in Nearby Cities
How other cities in Cook County handle adu rules.