Chicago allows ADUs in residential zones with moderate regulations. The city has recently liberalized ADU policies to address housing affordability, with streamlined permitting for qualifying projects.
Zoning & Size Requirements
| Allowed Zones | Single-family residential zones |
| Max Size (Detached) | 950 sq ft |
| Max Size (Attached) | 800 sq ft |
| Max Size (JADU) | Not allowed |
| Max Height | 35 feet |
| Max Units | 1 ADU per lot |
Setback Requirements
| Rear Setback | 15 feet |
| Side Setback | 3 feet |
| Front Setback | 20 feet |
| Parking Required | 1 space per unit |
| Owner Occupancy | Not required |
| Min Lot Size | 4,500 sq ft |
Permit Process & Fees
| Approval Process | Building permit |
| Review Timeline | 60-90 days |
| Permit Fees | $2,800-$4,500 |
| Impact Fees | $1,000-$1,800 |
| Plan Check | 3-4 weeks |
| Pre-Approved Plans | Limited availability |
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Construction Costs
| Average Build Cost | $150,000-$300,000 |
| Cost per Sq Ft | $160-$315 |
| Garage Conversion | $80,000-$180,000 |
| Prefab ADU (Installed) | $110,000-$250,000 (installed) |
Finance Your ADU Project
Most ADU projects are funded through HELOCs, construction loans, or cash-out refinancing. Compare rates from top lenders in minutes.
Compare ADU Financing Options →Rental Income Potential
| Avg Rent (1 Bedroom) | $1,450-$1,950/mo |
| Avg Rent (2 Bedroom) | $1,850-$2,600/mo |
| Short-Term Rental | Not typically permitted |
| Est. Annual ROI | 5-7% annual return |
Explore Prefab ADU Options
Prefab ADUs can save 20-40% vs. traditional construction and cut build time in half. Compare top prefab manufacturers.
Compare Prefab ADUs →Recent Law Changes
What's Changed Recently
- 2024: Expanded ADU allowance in residential zones
- 2023: Streamlined permitting process
- 2024: Increased max detached ADU size from 850 to 950 sq ft
- 2023: Reduced parking requirements in select areas
Tips for Building an ADU in Chicago
- Chicago's strong rental market supports consistent income
- Higher property costs and construction expenses reduce ROI
- Long winters affect rental seasonality; budget accordingly
- Neighborhood diversity offers varied investment opportunities
Frequently Asked Questions
Can I build an ADU in Chicago?
Yes. ADUs are allowed in Single-family residential zones in Chicago. The maximum size for a detached ADU is 950 sq ft. No owner-occupancy is required.
How much does an ADU cost in Chicago?
ADU construction in Chicago typically costs $150,000-$300,000. Garage conversions run $80,000-$180,000, and prefab ADUs cost $110,000-$250,000 (installed).
How much can I rent an ADU for in Chicago?
Average ADU rents in Chicago are $1,450-$1,950/mo for a 1-bedroom and $1,850-$2,600/mo for a 2-bedroom unit.
Do I need parking for an ADU in Chicago?
1 space per unit. Check with Chicago planning department for the latest Illinois ADU parking rules, as many states have relaxed requirements in recent years.
How long does it take to get an ADU permit in Chicago?
The permit review timeline in Chicago is 60-90 days. Fees range from $2,800-$4,500.
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