ADU Rules: Arlington Heights vs Chicago
How do adu rules rules compare between Arlington Heights, IL and Chicago, IL?
Chicago has fewer restrictions than Arlington Heights.
Arlington Heights, IL
Cook County
Arlington Heights does not currently permit accessory dwelling units (ADUs) as a by-right use in most residential zoning districts. The Village's zoning ordinance generally limits residential lots to one principal dwelling. Coach houses or secondary units may be possible through a special use permit or planned development process, but approval is not guaranteed and requires public hearings.
View full Arlington Heights rules →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 →Key Facts Comparison
| Fact | Arlington Heights | Chicago |
|---|---|---|
| ADUs Permitted | Not by right in most zones | - |
| Special Use Permit | Required for secondary units | - |
| State ADU Mandate | Illinois has none | - |
| Accessory Living Space | Allowed without separate kitchen/entrance | - |
| Public Hearing | Required for zoning relief | - |
| 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 |
Highlighted rows indicate differences between cities.
Arlington Heights FAQ
Can I build a granny flat or ADU in Arlington Heights?
Not as a by-right use. ADUs are not permitted in most residential districts. You would need to apply for a special use permit or planned development amendment, which requires Village Board approval after public hearings.
Can I finish my basement as a living space?
You can create a finished basement living area, but it cannot function as a separate dwelling unit with its own kitchen, separate entrance, and address. It must remain part of the single-family dwelling and meet building code requirements for egress and ceiling height.
Does Illinois require cities to allow ADUs?
No. Illinois does not have a statewide ADU mandate. Each municipality sets its own zoning rules regarding accessory dwelling units. Arlington Heights has not adopted ADU-enabling legislation.
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.
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