ADUs are allowed in Downers GroveTypes:DetachedInternal
Types:DetachedInternal
Accessory Dwelling Unit (ADU) Rules for Downers Grove, IL
Is your property eligible for an ADU?
# of Properties
18,836
Owner-occupied
79%
Zoning districts
20
Avg Home Value
$162,117
Median Lot Size
0.26 acres
Avg Income
$128,249
Residential Types:
18,836 housing units
Residential
100%
Zoning Districts:
20,357 parcels · 20 districts
R-4
31%(6,275)
R-3
31%(6,270)
R-6
7%(1,522)
R-2
6%(1,217)
Other
25%(5,073)
ADU Rules
What can you build in Downers Grove, IL?
Downers Grove, IL follows state and local rules for Accessory Dwelling Units. Here is a concise overview of the local rules.
Eligibility
- –Internal / Attached ADU: By Right
- –Detached ADU: By Right
Interior / Attached ADU Size Limits
- –In the FT district, an internal or attached unit within the principal house may be no larger than the lesser of 1,000 sq ft or 40% of the primary structure’s floor area.
Detached ADU Size Limits
- –Maximum of 1,000 sq ft for a detached ADU in the FT (Fairview Transitional) district.
Max Units
- –R-1, R-2, R-3, R-4 (Detached; internal only): 1 extended family accessory housing unit inside the principal detached house per lot (only 1 principal building per lot).
- –Fairview Transitional (FT): 1 extended family accessory housing unit per lot of record; may be within the principal structure or an accessory structure.
Owner Occupancy
- –Owner must occupy the principal dwelling unit or ADU.
Parking
- –No ADU-specific parking minimum or maximum; residential parking applies (on-site only; no off-site for required spaces); tandem spaces may count if assigned to the same dwelling unit.
Rental Restrictions
- –Short-term rentals prohibited; tenancy must be month-to-month or longer.
- –ADUs may be occupied only by relatives of the primary unit’s occupants; no unrelated tenants or boarders.
- –Some districts require a related occupant and prohibit roomers/boarders in attached/internal ADUs.
What's allowed on your lot?
These are the municipality-wide rules. What's allowed on a specific property also depends on state laws, setbacks, floor area ratio, lot coverage, environmental constraints, topography, and other property-specific factors. Search your address on FutureLot to see what's allowed on your property.
Check my propertyHow can we help you?
Get matched with trusted local builders
Understand what's allowed on your property
Learn the key rules and size limits for ADUs
Is your property eligible for an ADU?
ADU rules in other Illinois municipalities
Rules change at the town line. Check the municipality your property is actually in.
DuPage County