Garage conversion rules in Chicago, IL — sometimes called garage-to-ADU or accessory living unit conversions — govern permits, ceiling height, egress, and parking replacement.
Chicago authorizes garage conversions to coach houses (detached ADUs) and conversion units (attic/basement ADUs) under the Additional Dwelling Unit Ordinance. The pilot ordinance (effective May 2021) was made permanent and city-wide by Ordinance SO2024-0008918, which the City Council passed 46-0 on September 25, 2025, with permits accepted starting April 1, 2026. ADUs are now allowed in single-family zones within the original pilot areas plus all multifamily zones citywide (except downtown).
Under Chicago's Additional Dwelling Unit Ordinance (Municipal Code Title 17, Zoning), the City distinguishes between Conversion Units (created within an existing building such as an attic or basement) and Coach Houses (detached structures, often above a converted garage). A garage may be converted into or replaced by a coach house in the rear 50% of the lot, subject to a 22-foot height limit. The ordinance does not require additional off-street parking when an ADU is added. The new city-wide ordinance (SO2024-0008918, effective April 1, 2026) expands the eligible area by approximately 135% beyond the original five pilot zones, and applies a Registered Apprenticeship Program labor standard for general contractors and subcontractors performing coach house work. All ADU projects require a pre-certification approval from the Department of Housing and a building permit from the Chicago Department of Buildings (DOB). Existing two-flat and multifamily buildings may also add basement/attic conversion units citywide outside downtown.
Converting a garage to habitable space or constructing a coach house without DOB permits is a violation of the Chicago Building Code (Title 14X) and Zoning Code (Title 17), with stop-work orders, fines from $200 to $1,000 per day under Municipal Code §1-4-090, and required after-the-fact permits or restoration. Failure to comply with the apprenticeship labor standard on a coach house permit can result in permit revocation.
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Side-by-side rule comparisons with other cities in Cook County.
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