ADU rules in Kent

Kent allows two ADUs per lot in any mix, including two detached units, and lists ADUs as an accessory use in every district where a detached single-family dwelling is principally permitted: A-10, NR-L, NR-S, NR-2, NR-3, NR-4A, NR-4B and the CM commercial manufacturing district. KCC 15.08.350(B)(1) counts as detached anything not built inside or as an addition to another dwelling, so a unit over a detached garage or joined only by a breezeway or shared roof is detached. A detached ADU may go anywhere on the lot that meets the zone setbacks; in the rear half of the lot it may come within two feet of the side and rear lines, and it may sit right at a lot line abutting a public alley unless the city plows that alley for snow. Ordinance 4517 (adopted June 30, 2025, effective July 30, 2025) rewrote the section to implement EHB 1337, replacing the 2023 rules adopted by Ordinance 4464.

The same two-per-lot allowance covers one attached plus one detached, or two attached, or two detached ADUs, so an internal or addition-style unit is fully allowed. KCC 15.02.003 defines an ADU as a habitable unit 'added to, created within, or detached from' a detached single-family dwelling, duplex, triplex, townhome or other housing unit, so basement and internal conversions and units carved out of middle housing all qualify. An attached ADU simply takes the setbacks of its zone rather than the relaxed detached-ADU setbacks. ADUs attached to or contained within an existing single-family residence are expressly exempt from Kent's residential design review.

The cap is a flat 1,000 square feet per unit, not a percentage of the house, and unused floor area cannot be shifted from one ADU to the other. Gross floor area follows KCC 15.02.170 but excludes space with less than seven feet of ceiling height, up to 200 square feet total of covered decks and porches, and, where a detached ADU is built within or above another accessory structure, that structure's own floor area. Detached ADUs may not exceed 24 feet in height, with chimneys, antennas and railings allowed four feet above that; attached ADUs follow the zone height limit (35 feet in NR-L and NR-S, 28 feet in NR-2, rising to 35 feet there if an existing dwelling or an 18-inch-diameter tree is retained). The zone's other development standards still bite: building coverage, site coverage, impervious surface and setbacks under KCC 15.04.170 continue to apply.

Kent removed owner occupancy entirely when it implemented EHB 1337. KCC 15.08.350(B)(9) states that a covenant limiting one of the dwelling units to an owner occupant is not required, and it lets the planning director release covenants recorded under the old rules, with the applicant paying the recording cost. Releasing the covenant does not disturb the established use of the ADU. This matches RCW 36.70A.681(1)(b), which bars a city from requiring the owner to live in the ADU or another unit on the lot.

The requirement sits in the parking chart at KCC 15.05.040(A) rather than in the ADU section, which cross-references it. Beyond the half-mile walk shed one space per ADU is required, but the planning director may waive even that where there are special circumstances of the property, its location or the right-of-way. 'Major transit stop' is defined at KCC 15.02.257.5 to include commuter rail stops, rail and fixed guideway stops, bus rapid transit routes including those under construction, and any fixed-route stop running at least every 15 minutes for five hours during weekday peak. The city's ADU and Middle Housing Mapping Tool, linked from the ReCode Kent page, is the practical way to check whether a specific parcel is inside the half mile.

An ADU permit is an administrative approval, not a hearing. KCC 15.08.350(B)(10) requires a completed and approved permit application for every ADU, with the economic and community development department setting the submittal requirements, and KCC 12.01.040(A) classifies the 'Accessory dwelling unit permit' as a Process II application decided finally by the planning director, appealable to the hearing examiner. No conditional use permit or public hearing is involved, and because ADUs are ordinarily SEPA exempt no notice of application is triggered under KCC 12.01.140(A). Building permits and the usual life-safety code review still apply, and detached units go through Kent's residential design review administratively as part of building permit review (attached and internal ADUs are exempt from it).

Nothing in KCC 15.08.350 limits who may rent an ADU or for how long, and the section expressly allows the ADU and the principal dwelling to be designated for separate ownership, noting that condominium creation is governed by state law (Chapter 64.90 RCW). Renting a unit out does trigger two city requirements: a business license for the rental property under KCC 5.14.030, and registration in the rental housing registration and inspection program under KCC 10.02.040(B), whose definition of a residential housing unit expressly includes ADUs. Short-term rental means lodging for fewer than 30 consecutive nights (KCC 15.02.055); it is an accessory use only in NR-S, NR-2, NR-3, NR-4A and NR-4B (not NR-L, A-10 or CM) and is conditioned by KCC 15.04.030(34) on a Kent business license, occupancy of the home by the owner or a nontransient tenant for at least six months each year, a cap of three rooms offered within the home or accessory structure, and compliance with Chapter 64.37 RCW. Because condition 34 is written around renting rooms, whether an entire ADU may be let short term is not squarely answered by the text; homeowners planning that should get a written determination from Kent planning.