ADU rules in Rockford

Rockford's Zoning Ordinance contains no accessory dwelling unit, coach house, carriage house or backyard cottage of any kind. Table 20-1 lists the household living types allowed in the RE, R-1, R-1U, R-2, R-3 and R-4 districts (detached house, townhouse, two-unit house, and since August 2026 three-unit and four-unit houses and multifamily), and Section 20-004-G makes the omission decisive: uses not listed in the table, and uses marked with the prohibited-use dash, are 'expressly prohibited'. Article 57 independently closes the backyard-building route, because the Zoning Officer may classify a structure as accessory only after finding that it 'is not intended for habitation or business use in residential districts' (57-002-C), and Section 91-040 defines a 'dwelling' to include any structure in a residential district where beds are placed or cooking facilities are installed 'at any time for any purpose'. A second detached house on the lot would also be a second principal building, which Section 30-004-I makes a mandatory planned unit development, a discretionary City Council process, and it would still have to clear the district's minimum lot area per dwelling unit of 7,700 sq ft in R-1 and 6,000 sq ft in R-1U.

There is no internal or attached ADU either, but a second unit inside the house is lawful in the districts where 'Two-unit house' is a permitted use: R-2, R-3 and R-4, where it is marked P. Section 90-002-B.3 defines a two-unit house as 'a building containing 2 dwelling units, both of which are located on a single lot or parcel (also referred to as a “duplex” or “two-flat”)', attached and on separate floors or side by side, so a basement or upper-floor conversion there is a duplex of two co-equal principal units, with no accessory-unit size, occupancy or owner-residence cap. In RE, R-1 and R-1U, which cover most of Rockford's single-family neighborhoods, a two-unit house is marked '-' and is prohibited; the only exception in Table 20-1 is a grandfather row carrying forward two-family structures 'legally established and originally constructed as evidenced by the original building permit, prior to March 28, 2011, with a minimum lot size of 7,700 square feet' as permitted uses in R-1. Where a conversion is allowed it is gated by minimum lot area per dwelling unit (3,850 sq ft in R-2, 2,900 in R-3, 1,450 in R-4, on a minimum 8,800 sq ft lot) and by the off-street parking schedule. Ordinance 2026-141-O, adopted August 3, 2026, added three-unit and four-unit houses as permitted uses in R-2, R-3 and R-4, but only for new construction: the new Section 20-005-C.3 says three- and four-unit houses in R-2 are 'permitted as new construction' and 'does not include conversion of existing structures'.

Because the ordinance has no accessory dwelling unit, there is no square-foot or percent-of-primary-dwelling cap to quote. What binds instead is Article 57: 'The total floor area of detached accessory buildings in an R-1 or R-1U districts may not exceed 720 square feet or occupy more than 30% of the area of a required rear setback, whichever is greater' (57-003-B); in the other residential districts the allowance is derived from parking, at 264 sq ft of accessory building space for each required parking space, so a house needing two spaces gets 528 sq ft (57-003-C). Detached accessory buildings in residential districts may not exceed 18 feet in height (57-003-E), must meet the principal building's front setback, and need only 2.5 ft side and rear yards (57-003-F, 57-003-G). None of that floor area may be lived in. For the one legal way to add a unit, a two-unit house in R-2, R-3 or R-4, there is no unit-size cap at all: the constraints are the district's minimum lot area (8,800 sq ft) and minimum lot area per dwelling unit (3,850 sq ft in R-2, 2,900 in R-3, 1,450 in R-4), plus a 40 percent impervious surface ratio in R-2, 60 percent in R-3 and 70 percent in R-4.

No owner-occupancy condition attaches to any residential use in the Rockford Zoning Ordinance. The question is largely moot for detached ADUs, which are prohibited outright, and for the one legal second-unit path, a two-unit house in R-2, R-3 or R-4, Table 20-1 marks the use P with no residency condition and no use standard in the 'use standards' column. Owner occupancy matters only downstream, in the Code of Ordinances: Section 17-43 of the Residential Quality Support Ordinance makes it unlawful for a dwelling unit of a residential rental property to be occupied or let 'except for an owner occupied dwelling unit' unless the owner has filed contact information with the city, so living on site avoids the rental registry, and Section 17-104 of the Short Term Rental Ordinance requires that all short-term rental permit applications 'be submitted by the property owner' and that 'permits shall not issue to any person not an owner of the property', which is an ownership test, not a residency test. Illinois has no statewide ADU statute that would impose or preempt an owner-occupancy rule; SB3726, the Rockford-sponsored bill that would have, is dead in committee.

There is no ADU parking ratio because there is no ADU. Parking Group A of the Section 50-003-F schedule governs detached houses, townhouses and two-flats: R-1 and R-1U require '2 spaces per unit; At least one of the required parking spaces must be located in a fully enclosed garage'; R-2 requires 2 spaces per unit for detached houses, 2 per unit for two-flats and 2 per townhouse, again with one enclosed; all other R districts require 2 spaces per unit for detached houses and 1.5 per unit for two-flats. So converting a house into a legal two-flat means four off-street spaces in R-2 and three in R-3 or R-4, on the same zoning lot. Ordinance 2026-141-O (August 3, 2026) left Group A alone for R-1, R-1U and R-2 and cut the Group B multi-unit ratio from 2 to 1.5 spaces per unit, and it capped residential lots at one driveway under the new Section 50-016-B, which limits how much of that parking can be added at the curb. One statewide overlay now qualifies all of these minimums: PA 104-0457, Art. 5 (People Over Parking Act), eff. 6-1-2026, bars any unit of local government from imposing or enforcing minimum automobile parking requirements on a development project (including a permit for construction or reconstruction of a dwelling) within one-half mile of a public transportation hub or one-eighth mile of a public transportation corridor, with an express home-rule limitation. Rockford has no rail transit station, so a hub or corridor could arise only from RMTD bus routes meeting the Act's 15-minute combined peak-frequency tests, most plausibly around the downtown transfer center; whether any street or intersection actually meets those tests was not verified from schedules, so where the Act applies in Rockford is recorded as unresolved rather than asserted.

It depends entirely on which path a homeowner takes, and the ADU path does not exist. A two-unit house in R-2, R-3 or R-4 is a permitted use, so the review is ministerial: a zoning clearance and certificate of zoning compliance from the Zoning Officer under Section 60-001, folded into the building permit ('any construction or alteration of a building or other structure and any new use of land or a building must be cleared with the Zoning Officer'), with no hearing. A detached second dwelling, or any second unit in RE, R-1 or R-1U, is a prohibited use rather than a special use, so no special use permit under Article 63 is available for it, and Section 64-001 forbids using a variation 'in lieu of a special use permit or zoning map amendment'. The realistic routes are therefore a zoning map amendment to a district that allows two-unit houses or a text amendment to the ordinance, both of which run through the Zoning Board of Appeals with a noticed public hearing and a final decision by City Council (Articles 62 and 63). Two principal residential buildings on one lot separately triggers mandatory planned unit development review under Section 30-004-I, another City Council decision.

Nothing in Rockford law bars long-term renting of a lawfully created dwelling unit, but Section 17-43 of the Residential Quality Support Ordinance makes it unlawful for any dwelling unit of a residential rental property to be occupied, let, rented or leased, other than an owner-occupied unit, unless the owner has registered the property and each unit with the community development department, with renewal every February 1; the ordinance also creates a chronic nuisance enforcement track against registered rentals. Short-term rental is separately regulated by Chapter 17, Article VII, added by Ordinance 2024-246-O (passed December 2, 2024, approved and published December 6, 2024), which is in force but not yet codified in the Municode book. Its findings recite that 'short term rentals are a commercial use of residential property that is not currently permitted under the City of Rockford Zoning Ordinance or the Code of Ordinances', and it requires an annual owner-only permit (17-101, 17-104), rental-registry identification of the unit as a short-term rental (17-106), a guest register (17-107), written notice to abutting owners before the first rental each year (17-108), one rental per 24 hours (17-110), no on-site or hourly-rate advertising (17-111), occupancy of two people per bedroom capped at 10 (17-112), on-site overnight parking with street parking barred unless the driveway cannot hold four vehicles (17-113), and no parties or event-venue use (17-114). Renting rooms in a house is not a separate zoning use in Rockford; the only in-residence lodging use is a bed and breakfast, a special use in every R district under Table 20-1.