ADU Rules: Chicago vs Oak Park
How do adu rules rules compare between Chicago, IL and Oak Park, IL?
Chicago and Oak Park have similar restriction levels.
Chicago, IL
Cook County
Chicago ADU Ordinance: permanent program effective April 1, 2026 citywide (with aldermanic opt-in for single-family RS zones). Pilot program active in 5 zones since 2021. Coach houses up to 1,200 sq ft.
View full Chicago rules →Oak Park, IL
Cook County
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.
View full Oak Park rules →Key Facts Comparison
| Fact | Chicago | Oak Park |
|---|---|---|
| Program | Permanent ordinance effective April 1, 2026 | - |
| Coverage | Citywide with aldermanic opt-in for RS zones | - |
| Pilot Zones | 5 zones pre-opted-in since 2021 | - |
| Max Size | 1,200 sq ft or 50% of primary dwelling | - |
| Height | 22 feet maximum | - |
| South/West/SW | 2 permits/block/year cap; owner-occupancy required | - |
| Code Reference | - | VOP Zoning Ord. (adopted 2017) |
| Max ADU Size | - | 1,000 sq ft |
| Units Allowed | - | 1 ADU per single-family lot |
| ADU Types | - | Coach house, attic/basement, standalone |
| Parking | - | No additional required |
Highlighted rows indicate differences between cities.
Chicago FAQ
Can I build an ADU on my property in Chicago?
Chicago ADU Ordinance: permanent program effective April 1, 2026 citywide (with aldermanic opt-in for single-family RS zones). Pilot program active in 5 zones since 2021. Coach houses up to 1,200 sq ft.
What are the size limits for an accessory dwelling unit in Chicago?
Program: Permanent ordinance effective April 1, 2026. Coverage: Citywide with aldermanic opt-in for RS zones. Pilot Zones: 5 zones pre-opted-in since 2021. Max Size: 1,200 sq ft or 50% of primary dwelling.
Oak Park FAQ
What types of ADUs are allowed in Oak Park?
Three types: a coach house above a detached garage, a converted attic or basement in a single-family home with a separate entrance, or a standalone detached ADU. Only one ADU is allowed per single-family lot.
How big can my Oak Park ADU be?
No ADU may exceed 1,000 sq ft under the Village of Oak Park Zoning Ordinance. The ordinance specifically prohibits second-floor flat conversions of the principal single-family dwelling.
Do I need extra parking for an Oak Park ADU?
No. The zoning ordinance requires no additional parking for an ADU beyond the two parking spaces required for a single-family home.
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