The amended municipal code allows for ADUs to be established by right in all multifamily, mixed-use, and certain business and commercial zoning districts. The code updates have additionally created a process to allow ADUs in some residential single family (RS) zoning districts known as “ADU-Allowed RS Areas.”

ADU-Allowed RS Areas are created and modified following the passage of ordinance by City Council, as codified in section 17-7-0754 of the Chicago Municipal Code. Certain ADU-Allowed RS Areas may have additional limitations that must be met in order to establish an ADU. 

Visit the eligibility page to determine if an ADU is allowed at your project address. The next section details limitations specific to ADU-Allowed RS Areas that could impact your application for pre-certification.  

Annual Block Cap Limits
Certain ADU-Allowed RS Areas have a limitation on the number of conversion units and coach houses, combined, that may be pre-certified on the same block during the same calendar year. To learn more about what constitutes a block, visit our FAQ page (Coming Soon!)

1. RS-1 districts allow for one pre-certification annually per block
2. RS-2 districts allow for two pre-certifications annually per block
3. RS-3 districts allow for three pre-certifications annually per block

Owner Occupancy
If there is an owner occupancy requirement within an ADU-Allowed RS Area, and the principal building is a detached house, the principal building must be occupied by the property owner to receive a pre-certification for an ADU. The owner occupancy requirement applies to both conversion units and coach houses.  If the property is not occupied by the owner at the time of pre-certification, the applicant does not qualify for an ADU pre-certification. To meet this requirement you will need to upload proof of residency documents with your application submission.

Two forms of documentation are required:  

1. Government-issued photo ID; and  
2. One of the following:  
   1. Property tax documents (most recent property tax bill or property tax exemptions documentation) 
   2. Current utility bill (gas, electric, internet, or water) showing the property owner’s name and project address 
   3. Recorded deed or title document 
   4. Most recent mortgage statement 
   5. Homeowner’s insurance policy declaration 

Administrative Adjustment
If an administrative adjustment applies, the project applicant must receive an administrative adjustment in order to establish an ADU. The applicant must follow all of the requirements necessary in the administrative adjustment process including payment of a $500 fee. This process is administered by the Department of Planning and Development (DPD). To learn more about the administrative adjustments please visit the DPD webpage.

The number of ADUs an applicant is allowed to establish on a property depends on the type of ADU, conversion unit or coach house, being established. Requirements for each are specified below. 

Conversion Units

The number of total conversion units allowed depends on:  

• The age of the principal building: the property’s principal building must be at least 20 years old to be eligible for a conversion unit.
• The number of existing legal units on a property.  

The number of conversion units a property is allowed to add is calculated at a 33% additional density rate. For example, a property with four or fewer existing dwelling units can add one additional conversion unit, the table below offers a full breakdown of allowed conversion units based off existing dwelling units. 

Short Term Rentals: No short-term leases or vacation rentals, such as Airbnb, are permitted in conversion units.

Parking Requirements: No additional parking is required. 

Coach Houses

Coach houses are detached accessory building separate from principal building on lot. A single coach house is allowed, either alone or in combination with a conversion unit(s). If there is an existing coach house on your property you may not need an ADU pre-certification to repair, remodel, or build an addition if the coach house is considered legally established.  Learn more about situations where pre-certification is not required here.

Important note for applicants building new construction homes: A coach house may only be constructed after the principal building.

Short Term Rentals: No short-term leases or vacation rentals, such as Airbnb, are permitted in coach houses constructed after 2021.

Parking Requirements: No additional parking is required. 

The following table offers a breakdown of the number of ADUs allowed to be added based on existing legal dwelling units on the property.  

*To add any number of conversion units, the principal building must be at least 20 years old. 
**One coach house unit can be added regardless of principal building’s age if the principal building is constructed first.  
Please note that for business and commercial districts additional restrictions may apply on the location of conversion unit. Refer to the ADU allowance by zoning district chart for details. 

EXAMPLE: In a property with 4 existing units in which the principal building was constructed in 2005, the property owner would be eligible to add one conversion unit and one coach house.