Thinking about a backyard coach house or a basement apartment on your Chicago property? You’re not alone. ADUs can add flexible space for family or long-term rental income, but the rules and steps can feel overwhelming. This guide shows you where ADUs work today in Chicago and how to start with clear steps, timelines, costs, and common pitfalls to avoid. Let’s dive in.
What counts as an ADU in Chicago
Chicago’s ordinance recognizes two main ADU types: a detached backyard unit known as a coach house, and a conversion unit created inside an existing building, such as a basement or attic apartment. The City launched a pilot program in 2021 to allow ADUs in specific areas while it evaluated expansion. You can review the program’s rules and process on the City’s ADU portal, including intake, eligibility, and design limits on the City’s official ADU page.
Where ADUs are allowed today
Chicago uses five pilot zones: North, Northwest, West, South, and Southeast. You must confirm that your address is inside a pilot zone before you apply. The City’s ADU map and portal list the eligible areas and outline the intake steps.
Zoning and property eligibility
- ADUs are permitted in many residential zoning districts in the pilot areas, including RS, RT, and RM categories. Always confirm your exact zoning before you plan.
- Conversion units require an existing building that is at least 20 years old.
- In some zones, additional limits apply. West, South, and Southeast zones require owner occupancy for some ADUs and cap permits at two ADUs per block each year. These limits do not apply in the North and Northwest zones. For a concise rundown of eligibility by district and building type, see the Cityscape ADU rules overview covering zoning and age requirements.
Physical design, size, and parking rules
- Coach houses can be up to 700 square feet of living area, and no part may exceed 22 feet in height above grade.
- Accessory buildings in the rear yard, including garages and coach houses together, may not exceed 60 percent of the required rear setback area. This often sets the maximum footprint on standard lots.
- ADUs do not trigger extra on-site parking, but you cannot remove existing required parking without zoning relief. The City’s ADU portal outlines these standards in detail.
Where ADUs tend to be feasible
Owners often find the path smoother on lots with generous rear setback areas or wider-than-standard dimensions and in the North or Northwest pilot zones that do not have per-block caps or owner-occupancy requirements. Older buildings can be good candidates for conversion ADUs. Early permit data and reporting point to more activity in North and Northwest zones and fewer projects in West, South, and Southeast zones due to added limits and site constraints, as noted in Cityscape’s coverage of early permits and adoption patterns.
How to start: a step-by-step plan
Step 1: Confirm eligibility
Check your address, pilot zone, and zoning district on the City’s site, then review the intake process on the City’s ADU page.
Step 2: Do quick feasibility checks
Measure your lot and calculate the 60 percent rear-yard accessory limit. For conversions, confirm the building is at least 20 years old and check basement clear heights and structural conditions. Cityscape’s explainer summarizes key thresholds for districts and building age.
Step 3: Complete the City’s ADU intake
Submit an intake application to the Department of Housing. Intake approval lets you move forward to the building permit application with the Department of Buildings. Intake is not a permit.
Step 4: Notify neighbors and your alderman
You must give written notice to adjacent owners and your ward office, then file an affidavit. The City provides templates and forms on its documents page.
Step 5: Prepare plans and submit for permit
Hire an Illinois-licensed architect or structural engineer to prepare plans. A City-licensed permit expediter can help, and you must use City-licensed trades for electrical, plumbing, and masonry.
Step 6: Plan for review timelines
Processing varies. Analyses of recent permit data show many projects taking several weeks to a few months, with averages roughly in the 66 to 122 day range from submission to issuance, depending on factors like self-certification and plan checks. Cityscape’s data summaries discuss typical durations and revisions across recent ADU permits.
Step 7: Build the right team
At minimum, line up a licensed architect or structural engineer, a general contractor, and licensed subs. If you are financing with grants or loans, look into nonprofits that offer guidance.
Step 8: Explore grants and forgivable loans
Neighborhood Housing Services has offered planning grants and construction funds structured as forgivable loans, subject to eligibility and program availability. Review NHS’s ADU manual for current details on grant and loan options.
Step 9: Record required affordability covenants if applicable
If your project triggers affordability requirements, the City will require a recorded covenant and rent limits tied to income levels. The City’s ADU portal explains when and how this applies.
Budget: realistic costs and what drives them
Costs vary by scope, site, and structure. Early permit data showed median construction costs around the mid five figures for many basement conversions, with coach houses in the higher five figures to low six figures, and some full projects reaching several hundred thousand dollars. Cityscape’s permit analysis highlights both the median and the wide range seen in Chicago ADU projects. Reporting also points to small size caps, setbacks, and structural upgrades driving costs, especially for coach houses, as summarized by the Chicago Sun-Times in its coverage of ADU costs and uptake.
Rules that surprise owners
- Short-term rentals are not allowed. You cannot lease an ADU for 31 days or fewer.
- ADUs do not require new on-site parking, but removing existing required spaces is not allowed without zoning relief.
- Some multi-unit conversions trigger long-term affordability requirements and a recorded covenant.
Common pitfalls and how to avoid them
- Do not assume intake equals a permit. Plan for plan checks and possible revisions.
- Get early structural and utility assessments. Basements and coach houses often need significant upgrades.
- Build a padded budget. Obtain multiple bids and include a contingency to cover surprises.
What could change next
City leaders have been working on proposals to expand or reform ADU rules citywide. As of 2025, the City Council’s Zoning Committee advanced broader ADU expansion efforts, with negotiations continuing and some revised limits under discussion. Keep an eye on council actions and ward updates, as reported by Axios on the latest ADU expansion push.
Quick homeowner checklist
- Verify pilot eligibility and zoning for your address.
- Measure your lot and check the rear-yard accessory limit and basement feasibility.
- Complete the City’s ADU intake.
- Send neighbor and alderman notices and keep your affidavit.
- Hire a licensed architect or structural engineer and line up licensed trades.
- Get 2 to 3 contractor bids and set a contingency.
- Review NHS grants and loan options if you qualify.
- Track City Council updates if you are outside the pilot area.
Ready to explore an ADU?
If an ADU could help your family or strengthen your investment strategy, you deserve a clear plan rooted in local rules and market realities. For tailored guidance on property selection, resale considerations, rental strategy, and permitting timelines across Chicago and the North Shore, connect with Meldina Dervisevic. We’ll help you plan confidently and move forward step by step.
FAQs
What is the difference between a coach house and a conversion ADU in Chicago?
- A coach house is a new detached backyard unit, while a conversion ADU is a new unit created inside the existing building, such as a basement or attic apartment.
Are ADUs currently allowed citywide in Chicago, or only in pilot zones?
- ADUs are allowed in five pilot zones; you must confirm your address is inside a pilot area before applying through the City’s ADU process.
Do Chicago’s ADU rules require me to live on-site as the owner?
- In the West, South, and Southeast pilot zones, some ADU types require owner occupancy and there is a cap of two ADU permits per block per year; these limits do not apply in the North and Northwest zones.
How big can a Chicago coach house be, and how tall?
- The maximum living area is 700 square feet and no element may exceed 22 feet in height above grade, with rear-yard footprint limits also applying.
How long do ADU permits usually take to get approved in Chicago?
- Timelines vary, but recent analyses show many projects taking several weeks to a few months, often in the 66 to 122 day range depending on plan review and self-certification.
Can I use a Chicago ADU for short-term rentals like Airbnb?
- No, Chicago prohibits renting an ADU for 31 or fewer consecutive days; only standard long-term leasing is allowed.
Will I need to add parking when I build an ADU in Chicago?
- ADUs do not require new on-site parking, but you cannot remove existing required spaces without separate zoning relief.
