Illinois ADU Laws

Complete 2026 guide to accessory dwelling unit regulations

○Local Control Only

📋Quick Facts

Max Size
900 sq ft
Size Limit
50% of primary
Owner Occupancy
May be required
Parking
Set locally
Approval Process
Varies locally

📜Recent Legislation

HB 4213 (2024) - Local Accessory Dwelling Unit Act - FAILED January 2025

HB 3552 (2025) - Local-Accessory Dwelling Units - Proposed

⚠️Key Requirements & Restrictions

  • •No statewide ADU law
  • •Chicago has pilot program (December 2020) limited to 5 areas
  • •Rules vary by municipality

📖Detailed Analysis

No statewide ADU law. HB 4213 failed in January 2025. New HB 3552 proposed for 2025-2026. Chicago lifted ADU ban in December 2020 with pilot program in 5 strategic areas. Chicago rules: max 50% of main house or 900 sqft (whichever smaller), must have own entrance, kitchen, bathroom, sleeping area. Outside Chicago, rules vary entirely by municipality.

🔗Official Resources

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⚠️ Disclaimer

The information provided on this website is for general informational purposes only and does not constitute legal, financial, or professional advice. ADU laws, regulations, and requirements vary by jurisdiction and change frequently. While we strive to keep this information accurate and up-to-date, we make no representations or warranties of any kind about the completeness, accuracy, reliability, or suitability of this information. Always consult with qualified local professionals, including attorneys, architects, and your local planning department, before making any decisions regarding ADU construction or investment. Use of this information is at your own risk.

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Last updated: February 2026