ADU rules in Champaign

Champaign legalized ADUs with Council Bill No. 2022-117, adopted June 21, 2022, which added Division 9 to the zoning ordinance. Section 37-627 permits ADUs of any type, including a freestanding Detached ADU, in every Residential Zoning District listed in Table III-A: SF1, SF2, MF1, MF2, MF3, MFUniv, MHC, IT-SF1, IT-SF2, IT-MR1, IT-MR2 and IT-MX. One ADU is allowed per lot. A detached unit may not sit between the principal building's front line and the front lot line, is capped at 24 feet tall, and must meet the principal structure setbacks of the underlying district rather than the lighter two foot accessory structure setbacks, unless it converts or rebuilds on a detached accessory structure that is more than ten years old. ADUs are not authorized on commercially or industrially zoned lots, even where a house stands there.

Section 37-626 recognizes two non-detached forms: an Attached ADU that expands the principal structure and is self-contained with a separate means of egress, and an Internal ADU wholly inside the existing principal structure with a separate means of egress and no expansion. Section 37-627 permits ADUs 'in any type defined herein' throughout the residential districts, so basement, addition and internal conversions are treated the same as backyard cottages for use purposes. Attached and internal units take the height limit of the underlying district (35 feet in SF1 and SF2) instead of the 24 foot detached cap, and unlike detached ADUs they count toward the district's floor area ratio, open space ratio, maximum building footprint and maximum lot coverage. The same 600 or 800 square foot size cap and one per lot limit apply.

Section 37-628(b) ties the cap to lot area alone, with no percentage-of-house test. Floor area means gross floor area measured to the outside walls under the section 37-20 definition. Height: 24 feet for any detached ADU, including the combined total where the unit is built with a detached garage; attached and internal units take the underlying district maximum. Where a detached ADU is combined with a detached garage, only the living space counts against the ADU cap and the garage counts against the separate accessory structure allowance (625 square feet aggregate for detached accessory structures on a single-family lot, or 50 percent of the principal structure's above-grade floor area if that is larger, under section 37-222(a)(4)), but the combined structure may never exceed the ADU size allowance in floor area terms.

Division 9 imposes no owner occupancy condition, at application or on an ongoing basis. Section 37-628 runs from (a) number of units through (m) building code compliance, and none of its thirteen subsections mentions owner occupancy; the phrase appears nowhere in Chapter 37 in connection with ADUs. The zoning ordinance plainly knows how to require it when it wants to: a bed and breakfast is defined as an owner-occupied single-family detached dwelling and section 37-243(a) requires the owner to occupy the property and operate the business. Comparing the current text with the pre-2025 version stored in the Municode code bank confirms the requirement was never there and was not quietly removed: Council Bill No. 2025-037 (adopted March 18, 2025) changed only the words 'square footage' to 'floor area' in subsections (b) and (c)(2). Illinois has no statewide ADU statute, so nothing preempts a local owner occupancy rule; Champaign simply did not adopt one.

Section 37-628(h) waives both vehicle and bicycle parking for the ADU itself. The proviso does real work: under section 37-359.2 a single-family or duplex dwelling owes two off-street spaces per dwelling unit, so a house that is short of its own two spaces has to cure that before the ADU exemption applies. Detached ADUs are also exempt from floor area ratio, open space ratio, maximum building footprint and maximum lot coverage, which removes the other common site-capacity obstacle. Champaign's City Council has directed staff to eliminate minimum off-street parking citywide as Phase 1 of its Incremental Development goal, and the draft Chapter 37 rewrite that the Plan Commission recommended for approval on August 5, 2026 deletes the parking ratios entirely, which would make this proviso moot.

Section 37-627 makes ADUs a permitted use, not a provisional or special use, so there is no public hearing, no Plan Commission or Zoning Board of Appeals action and no discretionary approval. The only approval is a building permit: section 37-628(m) requires the unit to comply with all building code requirements and be approved for a building permit before construction, and the Zoning Administrator reviews that permit application for zoning compliance under sections 37-683 and 37-685 and approves or disapproves it administratively. The planning and zoning fee schedule at section 19-8.15 carries no ADU or ADU-specific application fee, which corroborates that no zoning case is filed; the ordinary one and two family building permit fees and a five business day plan review target apply. One overlay can add discretion: on a designated Landmark, inside a Historic District, or for any new building on a lot in a Conservation District, a Certificate of Appropriateness is required and may go to the Historic Preservation Commission.

Nothing in Division 9 bars renting an ADU, and there is no primary-residence test. Three limits shape the tenancy. Section 37-628(j) caps occupancy at no more than two persons unrelated to each other by blood, marriage or legal adoption, which is tighter than the general section 37-20 'family' definition allowing up to four unrelated people in a dwelling unit, and matters in a university town. Section 37-628(k) forbids home occupations and any other business use inside the ADU. Section 37-628(l) forbids selling the ADU separately from the principal structure. Separately, since Council Bill No. 2026-052 (adopted April 21, 2026) every rented dwelling unit, expressly including accessory dwelling units and expressly regardless of lease duration and including short-term rentals, must be registered annually with the Neighborhood Services Department, with renewals due each March 1; enforcement and penalties do not begin until March 1, 2027. Renting to a relative of the owner exempts a single-family property from registration. The zoning ordinance itself neither licenses nor prohibits short-term rental of an ADU; the only transient lodging use it allows in residential districts is a bed and breakfast, which must be an owner-occupied single-family detached dwelling with no more than three rented bedrooms and a seven day maximum stay.