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Everything you need to know about Chicago ADUs

Updated: Feb 24

In December of 2020, Chicago's City Council approved an ordinance "designed to promote the establishment of new residential units within the existing neighborhood fabric without the need for City funding". The Additional Dwelling Unit (ADU) substitute ordinance will allow for the creation of ADUs in five areas around Chicago starting May 1st, 2021.

  1. What is an ADU?

ADU is short for Additional Dwelling Unit. It's a secondary dwelling unit that is either attached or detached to the primary dwelling. It must have a kitchen, bathroom(s), a living area and a separate entrance. In municipal code, there are two types of ADUs.

1) Additional conversion unit (ACU): This category can be a garage conversions, additions or interior units located within a house that has been in lawful existence for 20 or more years.

2) Coach house. This category is designed for detached ADUs.

Demo of the ADU concept, image adapted from Housable


2. Who can build it?

In 2021, five communities are allowed for ADU applications. They are:

  • 1. North zone: West Ridge, Edgewater, Uptown, Lake View, North Center, and Lincoln Square community areas.

  • 2. Northwest zone: Albany Park, Irving Park, Avondale, Hermosa, Logan Square, West Town, Near West Side, and East Garfield Park.

  • 3. West zone: East Garfield Park West Garfield Park, North Lawndale, and South Lawndale (Little Village).

  • 4. South zone: Ashburn, Auburn Gresham, West Lawn, Chicago Lawn, Washington Heights, Rosalind, Chatham, Greater Grand Crossing, Englewood, West Englewood, Washington Park, and Woodlawn.

  • 5. Southeast zone: South Chicago, East Side, South Deering, and Hegewisch.



All properties located in R zones, except RS-1, are allowed to submit ADU applications on May 1, 2021.


3. How many ADUs can I build?

If the primary house has equal or fewer than 4 dwelling units, it is allowed to have a coach house or one ACU.

If a building has 5 dwelling units or more, than the building cannot have a coach house. But it is qualified to have 2 or more ACUs. The maximum number of ACUs is determined by the equation:

{number of existing dwelling units} x 33%. Round to the nearest integer


For example, if the building has 8 dwelling units, then the maximum number of ACUs allowed is 8 x 33% = 2.64 -> 3 units.


It should be noted that 50% of the added ACUs shall be affordable housing units. In the example, this means 1 unit out of 3 (any fraction shall be rounded down to the nearest integer) unit should be designated for low-income household. A low-income house rental means you can only charge a less than 30% of the defined 60% AMI or below (see AMI table here: https://www.chicago.gov/city/en/depts/doh/provdrs/renters/svcs/ami_chart.html ) as rental fee.


Also, another very important factor is that the building qualified for adding interior units must be 20 years or older. If your building is less than 20 years old, then your choice will be limited to coach houses, additions and detached garage conversions.


4. Any size limitations?

As far as we know at this point, the maximum-sized coach house 700 sq.ft. and is limited to one dwelling unit - so only one functional kitchen is allowed. There is no limitation on the number of bathrooms and bedrooms. There is no size limitations for ACUs, however, for detached structure conversion, you may have to follow the existing layout, and for additions, it's subject to FAR and minimum lot area per unit. Your designer should be able to help you calculate those numbers.


5. Setbacks, FAR, rear yard coverage...?

ACUs are not subject to the open space provisions and minimum lot area per unit (except additions.) Also, it does not have requirements for setbacks.


Coach house are not subject to open space provisions, minimum lot area provisions and floor area ratio. It is required to keep 3' setback to side and rear and 15' undisrupted distance from the rear wall of the principle building to the front wall of the coach house.


Also, all accessory buildings (including coach house) shall not occupy more than 60% area of a required rear setback. For most of the lot, the rear setback is 28% of lot depth or 50', whichever is less).


For a 110' x 20' lot, it means your maximum coach house area is 616 S.F.


6. Height?

22' for a coach house.


7. Parkings?

No additional parking is required.


8. Vacant lots?

This is interesting piece of Chicago ADU code. According to the amendment, you can develop a coach house prior to the primary house! To do that, you have to

  1. Keep the coach house entirely within the rear setback.

  2. It will be exempt from the rear setback requirement (28% of lot depth or 50')

9. Any other things I need to know?

Yes. If your property is located at West, South and Southeast zones, there are some exceptions you may need to pay attentions.

  • For buildings with 1-3 dwelling units, they must be owner-occupied to add a coach house or an ACU.

  • No vacant lots is allowed for ADU development.

  • Only 2 ADU permits per block per year. The block is defined as both sides of the street between two intersecting streets.

The ADU registration fee is $500 per unit.


No short-term rental is allowed, including vacation rental. You cannot list the ADUs on any web platforms such as Airbnb. The fine is between $1,500 - $3,000 per day.

That's pretty much all the updates from the latest approval. Soon we hope to see the ADU applications flood the building department! Leave any questions you have in the comment and we will try our best to answer them.



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