Champaign, IL Accessory Structures: ADU Rules (2026)

B. 2025-037, defines three ADU types under Sec. 37-626: an Attached ADU expands the principal structure with its own separate egress; a Detached ADU is freestanding, including one combined with a detached garage, and may share utility connections with the principal structure; an Internal ADU sits wholly inside the existing principal structure without expanding it. Sec. 37-627 permits any of these types by right in every Residential Zoning District listed in Table III-A. Sec. 37-628 then sets the performance standards: only one ADU is allowed per lot; a Detached ADU is capped at 24 feet in height and cannot sit between the principal structure's front building line and the front lot line; setbacks match those required for a principal structure in the underlying district, though Attached and Internal ADUs use the underlying district's height limit instead of the 24-foot cap.

No additional off-street parking is required if the principal use already meets its own parking requirement. Detached ADUs behind the principal structure need at least 3 feet of clearance to the right-of-way for emergency access. Occupancy is capped at two persons unrelated by blood, marriage, or adoption, home occupations and other business uses are barred inside an ADU, and an ADU cannot be sold separately from the principal structure. Construction must meet all building code requirements and obtain a building permit before work begins.