ADU rules in Joliet

Joliet's zoning ordinance has no accessory dwelling unit anywhere in it: the words "accessory dwelling", "coach house", "carriage house" and "accessory apartment" appear zero times in the 314-page ordinance and zero times in the 951 KB Code of Ordinances. A detached backyard cottage is blocked twice over. Section 47-17.1(5) allows no more than one main building on a lot except inside a Planned Unit Development, and the R-1 accessory-use list at 47-5.3 (which R-1A, R-1B, R-2, R-2A and R-3 all adopt by reference) permits detached garages, sheds, greenhouses, gazebos and pools but no dwelling. Section 47-5.8 then closes the list: anything not expressly permitted is prohibited. The one accessory living use, 47-5.3(M) "living quarters of persons employed on the premises", is a servants-quarters clause tied to employment on the property, not a rentable ADU.

There is no internal or attached accessory unit either. In R-1, R-1A, R-1B, R-2 and R-2A the only residential principal use is a single-family dwelling (47-5.1(A), adopted by reference in 47-5A.1, 47-5B.1, 47-6.1 and 47-6A.1), defined at 47-3.5(E) as "a building designed exclusively for and occupied exclusively by one (1) family". Finishing a basement or an addition as a second unit with cooking facilities turns the house into a two-family dwelling under 47-3.5(F), which those districts prohibit outright. Two-family dwellings are allowed only in R-3, and even there only inside a Planned Unit Development as of right (47-7.1(B)) or by special use permit from the Mayor and City Council (47-7.2(B)(2)). Joliet's council has been granting these one address at a time: Ordinance 345-26 approved a duplex special use at 1216 Fairview Avenue on 2026-07-07, and Ordinances 259-25, 407-25, 451-25 and 503-25 approved use variations for two-unit residences in R-2, R-2A and R-3 during 2025.

Because Joliet recognises no ADU, the ordinance sets no ADU floor area or height ceiling. The caps that would bind an outbuilding are in the R-1 accessory-use section: detached accessory structures "are to be one-story in height and smaller in footprint (first floor square footage) to the principal structure unless otherwise approved by a variance", maximum shed height 15 feet to the roof ridge, and under 47-17.5 detached garages are capped at 20 feet to the ridge with 10-foot walls, one per residential property. Anything over 200 square feet must complement the house's materials and colours. If a second unit is instead authorised as a two-family dwelling in R-3, the binding numbers are lot-based rather than unit-based: 7,000 square feet of lot with 3,500 square feet per family, versus 7,500 and 7,500 for a single-family lot (47-7.4). Minimum unit sizes at 47-17.13 are 220 square feet for an efficiency, 450 for one bedroom, 600 for two and 800 for three, excluding cellar, basement and garage area.

Moot in practice: there is no ADU for an owner-occupancy condition to attach to. Joliet's zoning ordinance imposes no owner-occupancy requirement on any residential use in the single-family or R-3 districts. Two occupancy rules are worth knowing anyway. The single accessory living use, 47-5.3(M), is narrower than owner occupancy: it covers only "living quarters of persons employed on the premises". And once any dwelling unit is let, Chapter 8 Sec. 8-152(h) requires a rental registration certificate "for any dwelling unit where the owner is not occupying the unit, even if no rent is paid or if the unit is occupied by a relative", so non-owner occupancy triggers registration rather than being forbidden. A homeowner should not read this "no" as permission to build.

There is no ADU parking standard to quote because ADUs do not exist as a use. The rules that would govern a second unit are per-unit and strict. Section 47-5.6 requires that "each dwelling unit located in an R-1 zoning district shall have two (2) off-street parking spaces on the lot on which the dwelling is situated", and 47-6.6 repeats it for R-2. The citywide schedule at 47-17.17(N)(1) sets two spaces for each family unit in a one-family dwelling plus one space for every two roomers. In R-3, 47-7.6(C) requires three off-street spaces for a two-family dwelling on the lot. Parking may occupy no more than 50 percent of a required front yard and only on a paved, designated driveway. Joliet grants no transit-proximity reduction; the pending ETOD zoning update is scoped to look at parking minimums near the Gateway Transportation Center. 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)). It creates no ADU right in Joliet, but the Joliet Transportation Center is a Metra rail terminus and therefore a rail transit station under the act, so within a half mile of it the baseline two-space minimum cannot be imposed on new dwelling construction; bus-frequency tests were not verified.

No ministerial path to a second dwelling unit exists in Joliet; every route is discretionary and ends at the City Council. A two-family dwelling in R-3 outside a Planned Unit Development is a special use decided by the Mayor and City Council with the advice of the Board of Appeals (47-7.2(B)(2)), and the applicant must prove all seven criteria in 47-5.2(C) by clear and convincing evidence. In a single-family district the route is a variation of use under 47-17.28: a published notice, a posted sign, a Zoning Board of Appeals hearing and recommendation, with "the City Council ... vested with the final authority to approve or reject". A PUD use exception under 47-15A.5 is capped at less than 5 percent of the development's ground area. Rezoning to R-3 is the fourth route (Ordinance 201-26 ran a reclassification the other direction in April 2026). Read the enum as "a discretionary hearing at best", not as an available ADU permit.

Joliet does not restrict ADU rental because it has no ADUs; it does run a comprehensive rental regime over every lawful dwelling unit. Chapter 8, Article I, Division 15 (rewritten in full by Ord. 17950 on 2019-05-21, amended by Ord. 18095 in 2020 and Ord. 18411 in 2022) requires owners to register and be licensed, at $100 annually, and to reregister every year and within 30 days of a change of ownership; the penalty for non-compliance runs to $750 per violation per day. Single-family, two-family, multi-family and short-term rental dwelling units are all subject to systematic inspection under 8-152(e). Short-term rentals are regulated rather than banned: 8-151 defines a short-term rental unit as "a dwelling unit that is primarily owner-occupied except for the duration of any short-term rental period", 8-153.3 sets up an annual short-term rental registration and inspection on complaint, and 8-153.3(c) bars any dwelling classified Type IV from short-term rental use. Renting out an unlawfully created second unit would be a zoning violation regardless of registration status.