ADU rules in Bloomington

A detached backyard ADU is allowed anywhere a single-family detached house is the principal use, but only as a special use, so there is no district where one can be built over the counter. Section 44-908C(7) lists 'Accessory Dwelling Units (ADUs), by special use, subject to the provisions of § 44-908E' among the accessory uses permitted in addition to a district's own use list. Section 44-908E then adds gates that bite: the primary building must be a single-family detached dwelling and the owner's primary residence, the ADU must sit to the rear of the primary structure, and it must be reached from an alley or, where no alley exists, from a single driveway shared with the main house. A detached ADU is also an accessory building, so the bulk rules of § 44-908D apply, and Ord. No. 2026-060 (passed 8-24-2026, approved and published 8-27-2026) tightened them: nothing in a required front or side yard, nothing in front of the front face of the house, at least 10 feet from the principal building wall, 5 feet (raised from 3) from rear and side lot lines, 10 feet from an alley right-of-way where the vehicle entrance faces the alley, and nothing in a drainage or access easement. Any accessory structure over 120 square feet now also needs a permit from the Development Services Department before it goes in, and the online code will not show these changes until the next supplement.

An internal or attached ADU runs on exactly the same special use track and gets no easier treatment. Section 44-1605 defines 'Dwelling Unit, Accessory' as a residential dwelling unit on the same lot as a single-family dwelling unit, 'either within the same building as the single-family dwelling unit or in a detached building', so a basement, attic or addition unit is an ADU and § 44-908C(7)'s special use requirement reaches it. Section 44-908E is written for both forms: it is headed 'Accessory dwelling unit conversion and new construction', its height rule is limited to 'Detached accessory dwelling units', and E(4) requires that only one entrance face the front facade of the primary building, with ADU entrances on the side or rear facade. Ord. No. 2026-060 also sharpened the line between the two forms: an accessory building attached to, or now within 2 feet of, a principal building counts as part of the principal building and must meet the principal building's location rules, so a detached unit tucked against the house is regulated as an addition. Mobile and manufactured homes are excluded from the ADU definition outright.

Section 44-908E(2) caps an ADU at 800 square feet or 50% of the size of the primary building, whichever is less, so a 1,400 square foot house yields a 700 square foot ceiling and only houses of 1,600 square feet or more reach the full 800. Height for a detached unit is 80% of the subject district's maximum, or a height that is minor in character to the primary building, whichever is less; the R-1A, R-1B, R-1C and R-1H districts cap buildings at 35 feet, which puts that figure at 28 feet. Ord. No. 2026-060, passed 8-24-2026 and in force since its late-August publication, ended the old conflict with the accessory-structure table by replacing Table 908's flat 14-foot cap for residential districts with the same 80% test, and added a note that no accessory structure may exceed the height of the principal structure, so a low house lowers the ADU. The general accessory-building floor area limits, no more than 30% of the rear yard and no more than the principal building's ground floor or 1,000 square feet, can still bind first on a small lot, and the same ordinance extended that 1,000 square foot rule to every residential district, R-3A and R-3B included.

Section 44-908E(1) is explicit: 'The primary building shall be a single-family detached use and the primary residence of the owner of the property.' The requirement attaches to the main house rather than to the accessory unit, so the owner lives in the front house and the ADU is what can be rented out. It reads as a continuing condition of the use, not a one-time test at application, and because the ADU exists only under a special use permit, an owner who moves out risks the permit under § 44-1707. It also means an investor cannot add an ADU to a rental house, and a duplex or multifamily building cannot host one at all. Illinois has no statewide ADU statute and no preemption of local owner-occupancy rules, so nothing overrides this.

Section 44-908E(6) requires 'a minimum of one parking space ... for the accessory dwelling unit in addition to the parking space(s) required for the primary building', and Table 1208E in § 44-1208 says the same thing from the parking side: 'Dwelling Unit, accessory: 1 space per unit'. Two conditions make the space harder to supply than the number suggests: it cannot sit in the required front yard setback, and tandem parking, one car behind another, with the primary building's spaces is expressly prohibited. Since a single-family dwelling itself needs one space under Table 1208E, a house with an ADU must show two independently accessible off-street spaces, which on a narrow lot without an alley is often the binding constraint. Ord. No. 2026-060 reworked Article XII's general provisions in August 2026 without touching either the ADU space or Table 1208E, and Bloomington has adopted no amendment conforming its parking minimums to state law. PA 104-0457, Art. 5 (People Over Parking Act), effective 6-1-2026, bars any unit of local government from imposing or enforcing minimum automobile parking requirements on a development project (a permit to construct or reconstruct a dwelling qualifies) within one-half mile of a public transportation hub (any rail transit station, or an intersection of 2 or more bus routes with combined 15-minute peak frequency) or one-eighth mile of a 15-minute-peak bus corridor, binds home-rule units (Section 5-90), and grandfathers site plans approved before the effective date (Section 5-15(b)); Bloomington has no rail transit station (intercity Amtrak serves neighboring Normal, and intercity rail's status under the act's rail transit station language is unresolved in any case), so applicability turns entirely on whether any Connect Transit routes meet the act's 15-minute combined peak-frequency tests, which was not verified from schedules, and where, if anywhere, the act reaches Bloomington is recorded as unresolved.

Every ADU needs a special use permit; Bloomington offers no administrative or by-right route. Section 44-908C(7) allows ADUs 'by special use', and § 44-1707 sets the process: a petition and scaled site plan to the Development Services Department, a written staff report, at least one public hearing before the Zoning Board of Appeals, newspaper notice published 15 to 30 days before the hearing under § 44-1705A(1), findings of fact against the six standards in § 44-1707H, and then approval by City Council ordinance with whatever conditions the Council attaches under § 44-1707I. Practice matches the code: case SP-05-25, a special use permit for an accessory dwelling unit in the R-2 (Mixed Residence) District, was heard by the Zoning Board of Appeals on 10-15-2025, which adopted findings of fact, and was approved by City Council ordinance on 11-10-2025. Building permits under Chapter 10 are separate and additional, and under Ord. No. 2026-060 an accessory structure over 120 square feet also needs its own Development Services permit.

Nothing in Chapter 44 forbids renting an ADU, and § 44-908E(1) presupposes it: the owner occupies the main house, which leaves the accessory unit available to a tenant. Every owner of a building containing residential rental units must file an annual registration with the city under the Rental Property Inspection Program (Chapter 45, § 45-201, adopting IPMC Sec. 900.3), currently $65 per building, and joins the periodic inspection pool; failure to register carries fines of $50 to $500 per day. Sec. 900.3(d)(1) exempts owner-occupied single-family homes and the owner-occupied portion of a duplex or multifamily structure, so an owner adding a rented ADU should confirm with the Community Enhancement Division exactly what has to be registered. Short-term rental is not prohibited by zoning: Chapter 44 defines 'short-term rental' at § 44-1620 but attaches no use permission, standard or ban to it anywhere in the district regulations, while § 39-802A levies a 6% tax on renting a hotel or motel room, a term § 39-801 defines to include a short-term residential unit, meaning all or part of a dwelling rented for fewer than 30 days. Because the ADU exists under a discretionary permit, the City Council can still condition an individual approval against rental under § 44-1707I.