ADU rules in Olathe

Olathe's Unified Development Ordinance allows one ADU per lot, attached or detached, as an accessory use to a single-family dwelling in all residential districts (defined in § 18.90.020 as A, R-1, R-2, R-3 and R-4), the downtown districts and planned districts (§ 18.50.025.A.3, A.5). A detached ADU may be new construction or a conversion of an existing accessory building on the lot, and it must sit at least 6 feet behind the front of the house and at least 10 feet from the rear lot line while meeting the district's side setbacks (§ 18.50.025.A.4, C.1, C.2). Ord. 22-22 (adopted May 3, 2022) widened the allowance from the A, R-1 and R-2 districts to every residential, downtown and planned district and moved all ADU rules out of the use matrix into this one section. The unit must match the house's architectural style and materials, get its own address, and have easements dedicated for separate utilities (§ 18.50.025.C.3, C.4, C.9).

Attached ADUs, including a unit carved out of part of the house such as a basement or upper floor, are allowed on the same terms as detached ones (§ 18.50.025.A.2.a, A.4.c). The 6-foot front and 10-foot rear setbacks apply to attached additions but not to an ADU located entirely within the interior of an existing house (§ 18.50.025.C.1). The unit must have complete independent living facilities (kitchen, living room, bathroom and bedroom), and the size, two-bedroom, address and separate-utility rules apply to attached units too.

The cap is the smaller of 1,000 sq ft of gross floor area or 50% of the principal structure's floor area, with no more than two bedrooms (§ 18.50.025.C.5); on a 1,600 sq ft house that works out to 800 sq ft. Height is limited to two stories and to the height of the principal dwelling (C.6), and the ADU may not push lot coverage, including the house, above 75% (C.7). The Planning Official may approve exceptions to the size, location and architectural style requirements administratively, with appeal to the Board of Zoning Appeals (D.2, D.3). These numbers have been unchanged since Ord. 22-22 (2022), which kept the earlier 1,000 sq ft / 50% / two-bedroom formula.

No owner-occupancy requirement applies, at application or afterward. Neither the current § 18.50.025 nor the version Ord. 22-22 replaced in 2022 contains one, and a full-text search of the Municipal Code, the UDO and the ordinance records for 'owner occupied', 'owner-occupied' and 'owner occupancy' found no ADU provision. No Kansas statute requires or forbids an ADU owner-occupancy rule; 2026 SB 418 governs only the approval process. The purpose statement's examples (seniors, or families with elderly parents) describe intended living arrangements, not a condition of approval.

The ADU must provide one off-street parking space with access to a public street from the existing driveway, and that space may be located in the existing driveway serving the house (§ 18.50.025.C.10). The parking schedule lists 'Accessory dwellings (carriage houses, granny flats, echo homes)' at 1 space per dwelling unit and single-family detached houses at 2 per dwelling unit, so a house plus ADU counts 3 spaces (Table 18.30.160-2). The Planning Official's exception power in § 18.50.025.D.2 covers size, location and architectural style, not parking. Before 2022 the text placed the space in the established front yard of the house; Ord. 22-22 changed that to the existing driveway.

An ADU 'requires a building permit only and a separate administrative review is not required' (§ 18.50.025.D.1), so there is no special use permit, site development plan approval or public hearing. Exceptions to size, location and architectural style are decided by the Planning Official, with appeal to the Board of Zoning Appeals (D.2, D.3). The city's residential permit page routes ADUs through the same online application as a new single-family house (sealed plans, site plan, statement of special inspections, energy code compliance). This ministerial path already matches 2026 Kansas SB 418, which requires ADUs that meet the local zoning criteria to be approved by-right without planning commission or zoning board review.

Nothing in § 18.50.025 or elsewhere in the UDO limits renting an ADU long-term or requires the owner to occupy either unit; the UDO defines a dwelling unit as one 'designed for and used or held ready for use as a permanent residence by one (1) family' (§ 18.90.020). Olathe has no short-term rental ordinance, license or registration: full-text searches of the Municipal Code, UDO and ordinance records for 'short-term', 'short term rental', 'vacation rental' and 'Airbnb' return no rental provision. The closest listed use, 'Bed and Breakfast' (temporary accommodations to overnight guests for a fee in a single-family detached dwelling), needs a special use permit from the Governing Body in the AG, R-1 and R-4 districts and is not listed in R-2 or R-3 (§ 18.20.500), so nightly rental of an ADU is worth confirming with the Planning Division. The code has no separate-sale clause; an ADU is defined as accessory to a principal single-family dwelling on the same lot (§ 18.50.025.A.2).