Garage Conversions: Chicago vs Des Plaines
How do garage conversions rules compare between Chicago, IL and Des Plaines, IL?
Chicago and Des Plaines have similar restriction levels.
Chicago, IL
Cook County
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).
View full Chicago rules →Des Plaines, IL
Cook County
Des Plaines City Code Section 12-8-1 caps detached garages and carports at 720 square feet in floor area and 15 feet in maximum height for residential lots. A building permit is required from the Department of Community and Economic Development before construction, and Cook County electrical inspection rules apply to any wiring.
View full Des Plaines rules →Key Facts Comparison
| Fact | Chicago | Des Plaines |
|---|---|---|
| Ordinance | SO2024-0008918 (passed 9/25/2025) | - |
| Effective Citywide | April 1, 2026 | - |
| Coach House Height | 22 ft max; rear 50% of lot | - |
| Parking | No additional spaces required | - |
| Labor Standard | Reg. Apprenticeship Program (coach houses) | - |
| Code Reference | - | Des Plaines City Code §§ 12-7-2, 12-8-1 |
| Max Garage Size | - | 720 sq ft |
| Max Height | - | 15 feet |
| Other Accessory Cap | - | 225 sq ft |
| Permit Office | - | Community & Economic Development (847-391-5380) |
Highlighted rows indicate differences between cities.
Chicago FAQ
Can I legally convert my Chicago garage to a coach house?
Yes, in eligible zones. As of April 1, 2026, Chicago's permanent Additional Dwelling Unit Ordinance (SO2024-0008918) allows coach houses citywide in single-family zones within the original pilot areas plus all multifamily zones (except downtown), with a 22-foot height limit in the rear 50% of the lot.
Do I need a permit to remodel or convert my Chicago garage to living space?
Yes. The Chicago Department of Buildings requires a building permit for any change of use from garage to habitable space, with plan review under Title 14X (Chicago Building Code). For ADU/coach house conversions, a pre-certification from the Department of Housing is required first.
Do I need additional parking after converting my Chicago garage?
No. The Additional Dwelling Unit Ordinance does not require additional off-street parking when adding an ADU, even when the conversion eliminates an existing garage.
Des Plaines FAQ
How big can a detached garage be in Des Plaines, IL?
Up to 720 square feet of floor area and 15 feet in maximum height under Des Plaines City Code §§ 12-7-2 and 12-8-1. Sheds and other non-garage accessory structures are limited to 225 square feet.
Do I need a permit to build a garage in Des Plaines?
Yes. A building permit from the Des Plaines Department of Community and Economic Development is required before construction. Electrical work must meet the Cook County Electrical Code.
Can I convert my garage into living space in Des Plaines?
Only with a change-of-use permit from the Building Division. Converted space must meet IRC residential requirements: egress windows, ventilation, ceiling height, insulation, smoke and CO alarms, and zoning parking-replacement rules.
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