What to know about Chicago’s permanent ADU ordinance

The pilot replacement takes effect in less than four months

Updated on January 8, 2026, to update the two maps; updated again on February 19, 2026, to update the same two maps.

The ADU pilot program that was meant to last only three years will expand and become permanent starting on April 1, 2026. Accessory dwelling units, or ADUs, are small homes that are either inside of a building or in a detached building behind a house. They were largely made illegal to build in 1957, but since May 2021 have been permitted in five pilot areas.

These pilot areas will go away on April 1, 2026, and ADUs will be permitted in more of the city. Chicago City Council voted 46-0 to approve ordinance SO2024-0008918 (PDF) on September 25, 2025.

What follows is a long FAQ-style article about the permanent ADU program. It does not require that you are familiar with the current pilot program. I have an additional resource: in November I presented about ADUs to the Coalition for a Better...