Chicago's ADU Rules Went Citywide in 2026 — But Not for Everyone

Chicago's coach house is legal again. On April 1, 2026 the city's Additional Dwelling Unit pilot became a permanent citywide ordinance, after City Council approved it 46–0 the previous September. Eligible parcels went from roughly 116,000 to over 320,000. But "citywide" is doing a lot of work in that sentence: whether you can actually build one on a single-family block still depends on your ward, there are caps on how many go up per block per year, and there is a labour requirement that catches most homeowners by surprise.

Multi-unit zones: yes. Single-family blocks: ask your alderperson.

In the multi-unit residential zones — RT and RM — and certain B and C commercial zones, ADUs are now allowed as of right across the city, outside the downtown core. That is the genuinely new part and it is what "citywide" refers to. Single-family RS zones are different: they depend on the ward alderperson having opted in, and at the time of writing that is 34 of the 50 wards. So two identical bungalows on identical lots can get different answers because of a ward boundary. Before you spend anything on drawings, find out which zone your lot is in and, if it is RS, whether your alder has opted in.

The per-block caps nobody mentions

Even in an opted-in single-family ward, there is a queue. The ordinance sets per-block annual caps by district: one per year in RS-1, two in RS-2, three in RS-3. If your neighbours got there first, you wait for the next year. This is the detail most likely to change your timeline rather than your eligibility, and it is worth checking early — a permit that is technically allowed but capped out for the year is still a permit you are not getting this year.

Your contractor needs an apprenticeship program — ask before you sign

This is the requirement that catches people. Effective with the citywide ordinance on April 1, 2026, contractors building coach houses in Chicago must participate in a federally registered apprenticeship program. It is a labour-standards condition attached to the ordinance, and it materially narrows the pool of firms who can legally do the work. If you are collecting quotes, ask each builder directly whether they comply, and get the answer before you contract rather than after. A cheaper bid from a firm that cannot pull the permit is not a cheaper bid.

Coach house size is not a square-foot number

Most cities give you a flat cap — 800 sq ft, 1,000 sq ft. Chicago does not. A detached coach house is governed by bulk and setback standards instead, and is limited to 60% of the required rear setback area, with a height cap of 22 feet and a requirement to sit within the rear 50% of the lot. Side setbacks run about 2 feet depending on the underlying district. The practical effect is that your buildable size is a function of your lot's geometry, so two owners in the same zone can be entitled to quite different buildings. Work this out on your actual parcel before you fall in love with a floor plan.

Owner-occupancy, short-term rentals, and the two-ADU trap

Three conditions worth knowing together. Owner-occupancy is required on properties with two or fewer units, and in the West, South and Southeast pilot areas that extends to properties with one to three units. Short-term rentals under 30 days are prohibited for ADUs, so this is not an Airbnb play. And if you add two or more ADUs on a property, 50% of them (rounded down) must be rented affordable at or below 60% of area median income — for 30 years. That last one is a long commitment attached to what can look like a simple decision to add a second unit.

What this does and does not mean for Illinois

Illinois has no statewide ADU mandate in force. Chicago's rules are local, adopted by City Council, and they do not extend to Evanston, Oak Park, or anywhere else in Cook County — each of those sets its own. If you are outside the city limits, the Chicago ordinance is useful as a signal of where the region is heading, not as a description of your rights. Check your own municipality.