Garage conversion rules in Des Plaines, IL — sometimes called garage-to-ADU or accessory living unit conversions — govern permits, ceiling height, egress, and parking replacement.
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.
Detached garages in Des Plaines are governed by the zoning code's accessory-use chapter, Section 12-8-1 ('Accessory Uses and Structures'), together with the residential bulk matrix in Section 12-7-2. The maximum floor area of a detached garage or carport on a residential lot is 720 square feet; other accessory structures (sheds, gazebos) are capped at 225 square feet. The maximum height of an accessory structure is 15 feet measured to the highest point. No accessory building or roofed structure may encroach into the required front yard or corner side-yard setbacks for the lot's zoning district. Rear-yard coverage is calculated from the rear elevation of the principal house to the rear lot line. Before pouring footings, owners must obtain a building permit from the Des Plaines Department of Community and Economic Development, which reviews plans, structural details, and stormwater impact. Detached garages must be wired to the Cook County Electrical Code, and detached garage electrical work is treated as part of the dwelling's branch-circuit service. For garage-to-living-space conversions, owners must apply through the Building Division for a change-of-use permit and meet IRC requirements for habitable space (egress, ventilation, smoke and CO alarms, ceiling height).
Building or expanding a detached garage without a permit, or exceeding the 720 sq ft / 15 ft height caps, is a zoning violation. Code Enforcement may issue a stop-work order and require removal, alteration, or after-the-fact permitting (often at a higher fee). Continued non-compliance can be cited to the City's Administrative Hearings system under Chapter 1 of the City Code.
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