IL HB3552

Local governments in Illinois are prohibited from banning the construction or use of accessory dwelling units (ADUs), which are attached or detached residential units on the same lot as a primary residence

Regulations that effectively prohibit ADUs are banned, including those that: impose fees beyond building permit review, require off-street parking, mandate corrections to nonconformities in the principal dwelling, or impose design standards that would physically preclude construction

Local governments must approve or deny ADU permit applications within 60 days for lots with existing dwellings; applications not decided within 60 days are automatically deemed approved

ADUs of at least 1,200 square feet must be permitted, though local governments may impose reasonable size and location regulations similar to other accessory structures

Denied applications must include written comments specifying deficiencies and how to remedy them; applications cannot be denied based on existing nonconforming zoning conditions or building code violations that don't affect public safety or the ADU construction