IL SB4071

Requires all Illinois municipalities to authorize accessory dwelling units (ADUs) by ordinance beginning January 1, 2027

ADUs must be permitted in all single-family zoning districts without additional requirements for lot size, setbacks, aesthetic standards, design review, frontage, or space limitations beyond what applies to the primary dwelling

Prohibits municipalities from requiring extra parking spaces for properties with ADUs, mandating familial relationships between ADU and primary dwelling occupants, or setting minimum/maximum limits on ADU square footage or bedroom count

Municipalities may limit properties to one ADU per single-family dwelling, and ADUs may be built simultaneously with the principal dwelling or converted from existing structures like garages, attics, or basements

Limits home rule powers, preventing municipalities from regulating ADUs inconsistently with state requirements