Bellevue vs. Kirkland ADU rules
Bellevue abolished its ADU registration entirely in 2023 (Ordinance 6746), while Kirkland still requires an ADU permit, an owner affidavit, and a covenant recorded with King County (KZC 115.07(9)) — genuinely more paperwork. Pre-approved plans are the bigger practical gap: Kirkland runs an active, city-vetted DADU plan gallery with expedited review today, while Bellevue's equivalent program is still in development, not live. Parking is more forgiving in Kirkland too — the first ADU never requires a space, even outside the transit-proximity waiver, where Bellevue's rule (LUC 20.20.120.C.5) can still require one beyond 1,000 sq ft. Size caps match at 1,200 sq ft in both cities.
✓ Verified against code · August 19, 2026
Bellevue rules run under LUC 20.20.120 (Land Use Code), adopted by Ordinance 6851, in effect since July 1, 2025.
✓ Verified against code · August 19, 2026
Kirkland rules run under KZC 115.07 (Kirkland Zoning Code), adopted by Ordinances O-4905 / O-4913, in effect since June 1, 2025.
Rule by rule
| Rule | Bellevue | Kirkland |
|---|---|---|
| ADUs allowed per lot | Two ADUs per lot in any district that allows a single-family dwelling — attached, detached, or a mix. No new ADU on a unit lot created by unit-lot subdivision.LUC 20.20.120.C.1, .C.7Previously: Detached ADUs were prohibited entirely; attached only — changed by Ord 6851, adopted June 24, 2025 | Two ADUs per single-family dwelling — one attached plus one detached, or two of either type. ADUs don't count as 'dwelling units' for one-unit-per-lot limits.KZC 115.07 (introductory) |
| Maximum size | 1,200 sq ft maximum per ADU. Up to 300 sq ft of parking or unheated storage per ADU is excluded. The Director may approve more for a single-floor attached ADU, an addition to an existing detached accessory structure, or a conversion; guest-cottage conversions are exempt from the cap.LUC 20.20.120.C.3 | 1,200 sq ft of gross floor area per ADU. Excluded: floor area under 5-ft ceilings, uncovered rooftop decks and at-grade patios, and up to 200 sq ft of exterior elements. The Planning Director may allow a larger attached ADU occupying an entire existing floor.KZC 115.07(4)(a)–(c) |
| Detached ADU height | 24 ft to the highest point for a detached ADU; 28 ft when built as an addition over an existing accessory structure. (Principal units get 32–35 ft.)LUC 20.20.120.E.1; Table 20.20.538.C.1 fn 9 | The zone's single-family height applies: 25 ft above average building elevation in RS/PLA 3C/PLA 6E, 30 ft in RSX/RSA/PLA 16. A DADU sited within the reduced 5-ft rear yard is capped at 15 ft.KZC 115.07(5); 15.30.060; 115.115(3)(o)(3) |
| Detached ADU setbacks | Same dimensional standards as middle housing: side 5 ft; rear 15 ft (LL-1 through SR-2 districts) or 10 ft (SR-3 through MDR-2); front 10–25 ft by district. A DADU may be sited at a lot line that abuts an alley. Conversions of existing structures are allowed despite nonconforming setbacks.LUC 20.20.120.E.2, .C.4; Table 20.20.538.C.1 | Zone single-family setbacks apply (RS: front 20 ft, sides 5 ft each, rear 10 ft). A DADU without alley access may come within 5 ft of the rear line (with the 15-ft height cap), and may extend to the rear lot line where it abuts an alley. Conversions of existing structures are exempt from setbacks and coverage if the nonconformity isn't increased.KZC 115.07(5)–(6); 115.115(3)(o)(3)–(4) |
| Off-street parking | None for ADUs under 1,000 sq ft; none within a half mile of a major transit stop; otherwise one space per ADU in addition to the primary structure's spaces.LUC 20.20.120.C.5, .B.1 | None within a half mile of a major transit stop. Beyond that, one space is required only when there's more than one ADU — and even that is waived if on-street parking exists within 600 ft or frequent transit is within a half mile. The first ADU never requires parking.KZC 115.07(7)(a)–(b) |
| Owner-occupancy | None. Removed by Ordinance 6746 in July 2023 — owners are not required to live on site, and the separate ADU registration was abolished at the same time.Ord 6746 §1 | None. The code affirmatively allows the ADU to be segregated in ownership from the house, and ADUs (except stacked ones) may be subdivided via unit-lot subdivision.KZC 115.07(2)–(3) |
| Lot coverage / floor area | Lot coverage 40–45% by district (the middle-housing table applies to DADUs). FAR treatment is asymmetric: attached ADUs are fully exempt from FAR and unit counts, while detached ADUs count toward both — making attached units 'cheaper' in zoning currency.LUC 20.20.390.A–.B; Table 20.20.538.C.1 fns 5, 10 | Zone lot coverage applies (50% in RS/RSA). FAR applies per zone, but the first 500 sq ft (lots under 8,500 sq ft) or 800 sq ft (8,500+ sq ft) of a DADU located behind the main structure is excluded from FAR — a real design lever.KZC 115.42(1)(c)–(d); 15.30.060 |
| Permit path & timeline | Permitted use — no conditional use permit and no ADU registration. Built under a standard building permit. The city publishes no ADU-specific review timeline; secondary sources suggest roughly 4–6 months for custom single-family-track review (estimate only).LUC 20.20.120.C.2, .C.4 | Permitted outright. Requires an ADU permit with owner affidavit, a registration covenant recorded with King County, and a standard building permit (via MyBuildingPermit.com). Expedited review is available; pre-approved plans use a reduced submittal list. No published timeline — secondary sources suggest 8–12 weeks standard.KZC 115.07(9) |
Bellevue: worth knowing
- Bellevue is the newest DADU market in the region — detached ADUs were illegal here until mid-2025, so almost no local DADU precedent or content exists.
- ADUs can be sold separately via unit-lot subdivision (LUC 20.45A.065 / 20.45B.057).
- An ADU cannot coexist with a Home Occupation Permit business on the same site (LUC 20.20.120.C.6).
- A pre-approved DADU plan program is in development (up to ~10 plans, launch anticipated 2026) but is NOT live yet — claims that Bellevue already has approved plan sets are wrong.
Bellevue: on our watchlist
Pre-approved DADU plan program launch anticipated in 2026, tied to the next state building code adoption. Watch for housekeeping Land Use Code amendments following Ord 6851.
Kirkland: worth knowing
- The pre-approved DADU plan gallery is real and active (designs by Cast Architecture, Fivedot, Ahouse Studio and others) — the homeowner pays a designer royalty capped at $1,000 and gets a permit-ready plan plus expedited review.
- Kirkland kept a covenant-recording step most cities dropped — one extra piece of paperwork at King County.
- The 500/800 sq ft FAR exclusion rewards siting the DADU behind the main house.
- The 'Kirkland ADU Toolkit' microsite is the best official homeowner resource in the region.
Full detail: Bellevue · Kirkland · back to the Washington hub. Not legal advice — every fact above cites the code section it comes from; check the cite, or ask your city’s planning department to confirm your specific lot.