ADU rules in Des Plaines, IL — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Des Plaines has no accessory dwelling unit (ADU) or coach-house ordinance; under Zoning Code Section 12-8-1 a permitted residential accessory structure is limited to a shed, gazebo, pergola, or detached garage and cannot be a separate dwelling, and Illinois has no enacted statute requiring cities to allow ADUs.
Des Plaines does not have an accessory dwelling unit (ADU), coach-house, or 'granny flat' ordinance. The City's official Community and Economic Development handout 'Residential Accessory Structures' and Zoning Ordinance Section 12-8-1 (Accessory Uses and Structures) define a residential accessory structure as a shed, gazebo, pergola, or detached garage or carport - not a separate dwelling unit. Under Section 12-8-1, an accessory structure must be 'incidental to the principal use,' 'subordinate in height, area, bulk, and location to the principal use,' and (other than a detached garage) is capped at 225 square feet and 15 feet in height, which physically rules out a habitable second residence. The City's permit handouts only list 'Accessory Structure - Shed, Gazebo, Pergola (Residential)' and 'Accessory Structure - Garage (Residential)' as permit types; there is no ADU permit category. Illinois does not currently mandate ADUs statewide: the proposed Local Accessory Dwelling Unit Act (HB3552, 104th General Assembly) was re-referred to the Rules Committee on March 21, 2025 and has not been enacted, so Des Plaines's local restriction controls. A homeowner who wants a livable second unit (for example, finishing a garage or coach house into living space) would need a use Variation or zoning relief from the Planning and Zoning Board.
Establishing a second dwelling unit in an accessory structure (shed, garage, or coach house) without zoning approval violates Section 12-8-1 and the use regulations of the underlying residential district. The Community and Economic Development Department can issue a notice of violation, order the unauthorized living space removed or vacated, and pursue citations; legalizing such a unit would require a Variation from the Planning and Zoning Board.
Other ordinances people look up for this city. Green dot = verified primary-source excerpt.
Des Plaines, IL
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