Bloomington, IL Accessory Structures: ADU Rules (2026)

Bloomington City Code § 44-908E allows Accessory Dwelling Units (ADUs) by special use under § 44-908C(7), then sets seven standards for building or converting one. Size is capped at 800 square feet or 50% of the primary building's size, whichever is smaller, and a detached ADU cannot exceed 80% of the height allowed in the underlying zoning district, or a height that reads as minor compared to the primary building. The ADU must sit to the rear of the primary structure and follow the same accessory-building location standards in § 44-908, including the 3-foot side/rear setback and 10-foot separation from the house.

Only one entrance may face the front facade of the primary building; the ADU's entrance has to open onto the side or rear facade instead, so the unit is not visible as a second front door from the street. Access should come from the alley where one exists; without alley access, the primary house and the ADU share one common driveway to the street. Parking requires at least one added space beyond what the primary house already needs, and that ADU space cannot sit in the required front yard setback or be a tandem space stacked behind the primary house's parking. Architecturally, the ADU must match the primary building and neighboring properties in roof pitch, eaves, materials, windows, trim and color.