ADU rules in Oak Park, IL — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Oak Park, IL allows accessory dwelling units (including the traditional 'coach house' built above a detached garage) under the Village of Oak Park Zoning Ordinance, originally adopted September 18, 2017 and amended through July 2, 2025. ADUs are capped at 1,000 sq ft, only one ADU is allowed per single-family lot, and no parking is required beyond the two spaces required for the primary single-family home.
Oak Park's Zoning Ordinance defines a 'coach house' as an additional dwelling unit located within a detached garage on the upper floor, associated with and incidental to the principal single-family dwelling on the same lot, with separate cooking and sanitary facilities and its own ingress and egress. The 2017 ordinance first allowed coach houses with full plumbing and kitchens. A 2021 amendment expanded the permitted ADU forms to also include conversions of attics or basements in single-family homes (with a separate entrance required) and standalone detached ADUs. ADUs are limited to 1,000 sq ft and only one ADU is allowed per single-family home. No additional parking is required beyond the two parking spaces required for a single-family home. The ordinance does not permit ADUs to be second-floor flat conversions of the principal dwelling. Standard Oak Park building permits are required from Permit & Inspection Services, and the unit must comply with the Illinois Smoke Detector Act (425 ILCS 60) and the village-adopted building code.
Operating an unpermitted ADU is a violation of the Village of Oak Park Zoning Ordinance, enforced by Permit & Inspection Services with citations and required compliance. Creating an ADU that exceeds 1,000 sq ft, adding a second ADU on the same single-family lot, or converting a second floor into a flat all violate the zoning ordinance.
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Side-by-side rule comparisons with other cities in Cook County.
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