ADU rules in Leavenworth

A detached ADU is allowed in any residential zoning district (R1-25, R1-9, R1-7.5, R1-6, R-MF, R4-16, RMX and MP) only through a special use permit, which takes a Planning Commission public hearing and a City Commission ordinance. Development Regulations §4.04.B.5.d lists ADUs among the accessory uses that 'shall only be permitted upon approval of a special use application by the city commission'. The provision dates from the 2019 text amendments; only one ADU special use permit had ever been issued as of September 2025 (Ord. 8254, 303 N. Esplanade, 12-10-2024), per city staff. A tiny home (a 200 to 400 sq ft site-built home on a permanent foundation) may serve as the ADU under §4.04.D.3.

§4.04.B.5.d does not distinguish detached from attached or internal units, so an attached ADU or a basement unit built out as a separate dwelling unit goes through the same special use permit in any residential district. Condition (6) requires the ADU to 'meet all building code requirements for a single-family dwelling unit'. City staff have said a kitchenette suite added inside the house is not a separate dwelling unit and so is not an ADU (BZA minutes, 10-18-2021); a unit rented separately would have to meet the dwelling-unit code requirements and the ADU rules.

Condition (4) caps the ADU at 900 square feet and at 33 percent of the principal dwelling's floor area, so the percentage controls for any house under about 2,727 sq ft (a 1,500 sq ft house allows about 495 sq ft). A detached ADU also counts toward the general accessory rules: all detached accessory structures together must be smaller than the house (attached garages and unfinished space excluded from the house figure), a lot may have no more than two detached accessory structures (three on 2 acres or more), and rear-yard accessory buildings need 3 ft side and rear setbacks and 5 ft from the house, never forward of the main building line. Structures at or above 15 percent of the house footprint must be architecturally compatible with it.

Condition (5) requires that either the principal dwelling or the ADU be occupied by the owner of the premises. It is a continuing permit condition: a special use permit continues only while it is used for its approved purpose and the annual SUP fee is paid, and violating a permit condition lets the City Commission rescind it (§2.04.C) or revoke it after a hearing (§2.04.D). The Board of Zoning Appeals has twice refused to vary the rule for owners living off site (2021, and Case 2025-15 at 771 Ottawa St. on 9-15-2025). Kansas has no owner-occupancy preemption.

Condition (7) requires lots with an ADU to 'contain a minimum of two off-street parking spaces, exclusive of garage space', and condition (3) bars a separate driveway entrance from the street. Separately, the parking table in §5.02 requires 2 spaces per single-family or two-family dwelling unit, and in the 2025 771 Ottawa case staff read that table as requiring 4 spaces in total for a house plus ADU. Which reading governs a given application is settled case by case in the special use permit.

Every ADU needs a special use permit under §2.04: an application with a certified 200-foot ownership list, a Planning Commission public hearing with published and mailed notice at least 20 days ahead, a possible protest petition (owners of 20 percent of the notice area force a three-fourths City Commission vote), and final approval by City Commission ordinance on discretionary findings (economic development or convenience, no substantial injury to neighboring property values, no domination of the neighborhood). The city's own page says the process 'may take up to 90 days'. This discretionary step is in tension with 2026 SB 418 §1(c)(1) (in effect 7-1-2026), and city staff proposed converting ADUs to permitted uses in response, but that amendment (Case 2026-27 TXT) was tabled on 9-14-2026 and had not been adopted as of 10-8-2026.

Nothing in §4.04.B.5.d bars renting the ADU or the house long term, as long as the owner lives in the other unit; the one ADU permit on record (303 N. Esplanade) is rented long term. Every rental dwelling, including 'rented dwelling units in owner-occupied dwellings', must be registered with the City Clerk under City Code Ch. 10, Art. XIII (one-time registration per owner, $20 per the city's page). Short-term rental is regulated as a 'Residential home-stay' (furnished, one limited-term boarder up to 180 days, registered as a rental property), which takes its own special use permit in R1-25 through MP and is permitted in RMX. Short-term stays also owe the city's transient guest tax (Charter Ord. 60 expressly covers Airbnb- and VRBO-type rentals). In 2025 staff told the BZA that the regulations do not allow a detached unit to be rented as well when the house runs as an Airbnb, and the variance was denied. There is no separate-sale provision; as an accessory use the ADU must stay on the same lot as the house.