About building an ADU in Chicago
Yes. Chicago's ADU ordinance (SO2024-0008918) takes permanent effect April 1, 2026. It allows new detached coach houses and conversions of existing structures in most residential zones (RS-1 through RT-4). ADU Checker instantly tells you if your specific lot qualifies.
RT (townhouse) and RM (multi-family) zones are eligible by right. RS (single-family) zones require aldermanic opt-in for specific blocks. Some B (business) and C (commercial) zones with residential uses also qualify. ADU Checker checks the city's live ADU eligibility map to determine your block's status instantly.
Typical new-construction coach houses cost $150,000–$350,000 depending on size, finishes, and site conditions. ADU Checker provides property-specific cost estimates that factor in your lot's risk flags — like flood zones, soil conditions, and demolition needs — so you get a realistic budget range.
Chicago's zoning code limits rear yard coverage to 60% of the rear setback area. This determines the maximum footprint of a detached coach house on your lot. ADU Checker calculates your available buildable area automatically using your lot's actual dimensions from Cook County records.
In RT, RM, and eligible commercial zones, ADUs are permitted as-of-right under the 2026 ordinance. RS (single-family) zones require aldermanic opt-in for specific blocks — some zones have no restrictions, while others require owner occupancy or have annual block caps. ADU Checker checks the city's live data and shows your block's specific rules.
The ADU Readiness Score (0–100) is ADU Checker's proprietary assessment of how feasible it is to build on your specific lot. It factors in zoning compliance, lot dimensions, existing structures, environmental risks, transit access, and neighborhood comparables. Higher scores mean fewer obstacles to construction.
The full text and resources are available on the City of Chicago's official ADU ordinance page. The ordinance (SO2024-0008918) was passed in 2024 and takes permanent effect April 1, 2026, replacing the earlier pilot program.
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Disclaimer: This information is educational and does not constitute legal, financial, or professional advice. Verify all information with the City of Chicago and consult licensed professionals before making decisions.