ADU Rulebook

City · Washington

ADU rules in Kirkland

4 sources

These are the primary sources for accessory dwelling unit regulations in Kirkland: the city's own zoning code, planning department pages, and permit guides. Start here before talking to anyone: the rules below are what your permit reviewer will apply.

Rules at a glance

Detached (backyard) ADU
Allowed

Two ADUs are permitted per single-family dwelling: one attached and one detached, or two of either type. A detached ADU must be fully contained in a separate structure and may not share a common roof structure with the principal unit or an attached ADU.

KZC 115.07, 115.07(5)
Attached or internal ADU
Allowed

An ADU may be added to or included within the principal unit. Up to two ADUs per single-family dwelling, in any combination of attached and detached.

KZC 115.07, 115.07(5)
Maximum size
1,200 sq ft gross floor area (attached or detached); for an attached ADU entirely within existing floor area on a single floor, the Planning and Building Director may allow a larger unit

Gross floor area excludes space with under 5 ft ceiling height, uncovered rooftop decks and at-grade patios, and up to 200 sq ft of other covered or uncovered exterior elements. Separately, KZC 115.42 excludes the first 500 sq ft (lots under 8,500 sq ft) or 800 sq ft (lots 8,500 sq ft and larger) of a DADU located behind the main structure from F.A.R.

KZC 115.07(4); KZC 115.42(1)(c)-(d)
Owner occupancy
Not required

The current section contains no owner-occupancy requirement, and expressly allows an ADU to be segregated in ownership from the single-family dwelling and (except stacked ADUs) subdivided via unit lot subdivision. Section was amended in 2025 (Ords. 4905 and 4913) after WA HB 1337. Value is based on the absence of any such requirement in the operative text.

KZC 115.07(2), 115.07(3)
Extra parking
None within 1/2 mile of a major transit stop, and none for a single ADU elsewhere; lots more than 1/2 mile from a major transit stop with more than one ADU must provide one off-street space, waived if on-street parking exists within 600 ft or the property is within 1/2 mile of transit with 15-minute commute-hour headways

The one-space requirement only triggers when a lot has more than one ADU and is far from major transit; the first ADU never requires added parking under this section.

KZC 115.07(7)
Approval process
Permitted use

ADUs are permitted outright with single-family dwellings; the owner applies for an ADU permit (or registration form if no building permit is needed) with the Planning and Building Department, signs an affidavit, and records a property covenant with the King County Recorder's Office. Planning Official decisions are appealable under Ch. 145 KZC.

KZC 115.07, 115.07(9)
Rental restrictions
No ADU-specific rental restrictions or minimum lease terms in KZC 115.07. Citywide, short-term rentals (under 30 days) require a business license, and KMC 7.02.300 limits STR frequency based on owner or agent occupancy of the property (unlimited if continuously occupied as primary residence; otherwise capped at 120 days/year with a nearby property manager) and allows at most two STR agreements at a detached dwelling unit at a time

KMC 7.02.300 (Ord. 4607, 2017) is written for short-term rentals of detached dwelling units generally, not ADUs specifically.

KZC 115.07; KMC 7.02.300(1), (2), (4)
The fine print: 7 caveats that can change the picture
  • Two ADUs are allowed per single-family dwelling (one attached plus one detached, or two of either type), more than the single ADU many directories assume.
  • ADUs must meet the base use zone's setbacks, height, and lot coverage for single-family dwellings, as modified by KZC 115.42 and 115.115(3)(o), so buildable size and placement vary by zone and lot.
  • Conversions of existing structures (including detached garages) to ADUs are exempt from current setback and lot coverage requirements if existing nonconformities are not increased (KZC 115.07(6)).
  • F.A.R. relief for DADUs is lot-size gated: the first 500 sq ft (lots under 8,500 sq ft) or 800 sq ft (lots 8,500 sq ft and larger) of a DADU behind the main structure is excluded from F.A.R. (KZC 115.42(1)(c)-(d)).
  • ADUs may be separately owned and, except for stacked ADUs, subdivided through a unit lot subdivision under KMC Title 22.
  • An ADU permit requires a signed affidavit and a covenant recorded with the King County Recorder's Office that runs with the land while the ADU exists.
  • DADUs on lots approved under historic preservation subdivision regulations must be located behind the historic residence.

Summarized from Kirkland's ordinance text, read July 2026; every row links the code section it came from. Rules often vary by zone and lot, so treat this as orientation, not a permit determination, and confirm with the planning department before you commit to a design.

Compare Kirkland with 5 nearby cities

ADU regulations

Short-term rental rules

Planning to rent your ADU on Airbnb or VRBO? Kirkland regulates short-term rentals separately; check these before counting on nightly rental income.

Washington statewide law also applies

Washington sets baseline ADU rights at the state level. Where local rules are stricter than state law allows, state law usually wins, so both are worth reading.

See Washington statewide rules

Spotted something outdated?

Zoning codes change. If a link is dead or Kirkland has updated its ordinance, report it and we'll verify against the official source.

Report a correction

Ready to build?

Planning an ADU in Kirkland?

Tell us about your project and we'll match you with vetted local designers and builders as we bring them online. No cost, no obligation.

Find a builderEstimate costs first