ADU rules in Springfield

Springfield's zoning code has no accessory dwelling unit category, and two separate provisions block a detached backyard unit. Section 155.068(b)(2) caps detached accessory buildings in residential districts at 18 feet and adds that in no case shall any portion of one be used as a dwelling unit. Section 155.010(c) independently provides that in districts permitting residential uses, not more than one residential building shall be located on a lot, so a second freestanding house is not an option either. The ban reaches every residential district, including the H-1, H-2 and H-3 historic districts, because § 155.277(b) makes historic-district accessory buildings comply with § 155.068. The one detached structure anyone may sleep in is a watchman's quarters at a business or industrial location (§ 155.043), which the code expressly says shall not be considered a dwelling unit.

There is no attached or internal ADU category either, so a second unit inside a house is simply a conversion to a duplex, and whether that is allowed depends entirely on the district. In R-1 the only permitted residential use is a single-family detached residence (§ 155.016(b)(1)), and § 155.001 defines a single-family residence as a building containing only one dwelling unit, so a basement, attic or addition apartment is not allowed in R-1 at all. R-2 permits duplexes (§ 155.017(b)), as do R-3, R-5, OFF and the H-3 historic district, so in those districts a homeowner can legally add a second unit, but as a co-equal duplex half rather than a subordinate ADU. Section 155.056(c) applies the full lot-area table to the resulting unit count for any conversion that increases the number of dwelling units, which in R-2 means 3,000 square feet of lot per unit.

Because Springfield has no ADU category, the code sets no ADU floor-area cap and no percent-of-primary-dwelling test. The binding numbers are different in kind. For detached accessory buildings, § 155.068(b)(2) allows a maximum height of 18 feet in residential districts and forbids any dwelling use, so no size makes a backyard cottage legal. Where a second unit is legal (R-2 and above, as a duplex), the limit is land rather than building size: § 155.056 requires 3,000 square feet of lot per dwelling unit for duplexes in R-2, R-3(a)/R-5(a) and R-3(b)/R-5(b). Principal-building height is capped at 35 feet in R-1 through R-4 (§ 155.058), and R-2 yards are 25 feet front, 3 feet on either side (10 feet total) and 20 feet rear (§ 155.061(d)).

Chapter 155 imposes no owner-occupancy condition on any dwelling. The question is largely academic in Springfield because ADUs are not permitted, but where a second unit is legal (a duplex in R-2 and above) the owner is not required to live in either unit, and the zoning code carries no affidavit, registration or recorded-covenant requirement. The only place owner occupancy appears at all is the definition of a tourist home or bed and breakfast inn, which § 155.001 describes as an owner occupied single-family detached residence renting no more than three bedrooms to transient guests. Illinois has no statewide ADU statute, so there is no state provision either imposing or preempting an owner-occupancy rule here.

Section 155.091(a) requires at least one accessory off-street parking space for each dwelling unit in single-family and duplex residences, so converting a house to a duplex in R-2 or above adds one required space. Section 155.090 confirms the minimums are keyed to the principal use and that accessory uses on the same zoning lot require additional spaces. Spaces must sit on the same zoning lot as the use served (§ 155.114(a)), and none may occupy a required front yard (§ 155.114(b)); a space between the required front yard and a single-family or duplex residence that is not on a driveway must be paved and screened four feet high (§ 155.114(c)). There is no transit-proximity, small-unit or downtown exemption anywhere in Article V, and multifamily buildings jump to 1.5 spaces per unit (§ 155.091(b)). Statewide preemption now overlays this: the People Over Parking Act bars a unit of local government from imposing or enforcing any minimum automobile parking requirement on a development project located within one-half mile of a public transportation hub or one-eighth mile of a public transportation corridor, and Section 5-90 makes it a limitation on home rule units, which includes Springfield. Where it applies, § 155.091(a)'s one-space-per-dwelling-unit minimum cannot be imposed or enforced on a new permit, subject to the Section 5-15(b) grandfather for a contract or site plan executed or approved on or before the June 1, 2026 effective date. In Springfield the practical beneficiary is the R-2-and-above duplex conversion rather than an ADU, since ADUs are not permitted here at all, and whether any Springfield location actually qualifies was not established: the city has no Metra or CTA rail transit, its Amtrak station is intercity rail whose status under the act's 'rail transit station' language is unresolved, and the bus-based tests would turn on SMTD route headways not verified here.

There is no ADU permit because there is no ADU use, and what a homeowner faces depends on the district. A detached unit is barred outright everywhere by § 155.068(b)(2), so the only conceivable route is a use variance or a rezoning, not a permit. In R-2, R-3, R-5, OFF and H-3, adding a second unit inside the house is a permitted duplex reviewed administratively: the zoning administrator must certify compliance with Chapter 155 before the building services department issues a building permit or certificate of occupancy (§ 155.241(a)). In R-1 no second unit is permitted at all, and the conditional-use catalogue at §§ 155.175 through 155.211 contains no accessory-dwelling or second-dwelling category, so there is no hearing to ask for. Properties in the H-1, H-2 and H-3 historic districts additionally route building permit applications to the historic sites commission, which has 45 days to act (§ 155.267).

Chapter 155 places no restriction on long-term renting a legally created dwelling unit, and Chapter 110 (Business Licensing) has no rental-registration or short-term-rental article across its 46 articles, so a long-term tenancy needs no city license. Short-term renting is far narrower. The only transient-lodging use the code allows in a house is a tourist home or bed and breakfast inn, defined in § 155.001 as an owner occupied single-family detached residence in which no more than three bedrooms are rented to transient guests on an overnight basis and in which breakfast only is served. Section 155.179 makes it a conditional permitted use requiring Planning and Zoning Commission findings on parking, signage and neighborhood effects, and it is available only in R-3, R-5(a), R-5(b), R-5(c) and OFF, not in R-1 or R-2. Short-term rental receipts are reachable by the city hotel tax, since § 100.00.2 defines hotel to include room and/or house rentals.