Kirkland ADU and detached ADU rules
Can I build an ADU or DADU in Kirkland?
Kirkland generally allows up to two ADUs and offers preapproved DADU plans, but a backyard unit still has to pass the property's zoning, FAR, lot coverage, trees, critical areas, utilities, and fire-access checks. Compare an attached conversion with a detached unit early because each follows a different FAR, permit, and fire-code path. Current parking guidance and fees also require care.
Quick definitions. An accessory dwelling unit (ADU) is a complete additional home on the same property. A detached ADU (DADU) is in its own building. FAR or GFA limits how much enclosed floor area the property may contain.
Bottom line
What the current rules mean
Each ADU may usually contain up to 1,200 square feet. A new DADU uses the underlying zone's height, yards and coverage, with special five-foot rear/alley options and a partial FAR exclusion when it sits far enough behind the main house. Residential-L shoreline properties are limited to one ADU, and exact fire, permit, utility and ownership paths change with the attached/detached configuration.
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Common homeowner questions
Answers to common Kirkland ADU questions
Can I build an ADU or DADU on my Kirkland property?
Often, yes. Kirkland generally allows up to two ADUs, but Residential-L shoreline property is limited to one, and every proposal still needs the correct zone, shoreline, existing-unit, FAR, coverage, tree, critical-area, access, fire, and utility screen.
How large can a Kirkland ADU or DADU be?
The usual maximum is 1,200 square feet for each ADU. A narrow attached-unit exception can use more existing area on one floor, while the conditional 500- or 800-square-foot DADU FAR exclusion changes the floor-area calculation, not the ADU size limit.
Do Kirkland's preapproved DADU plans skip permit review?
No. A preapproved design can reduce building-design work, but it still needs a plan license, site adaptation, zoning and survey review, structural work, fire and utility decisions, drainage, trees, and the required permits for the actual property.
Does Kirkland require off-street parking for an ADU?
The controlling ordinance waives ADU parking within a half-mile of major transit and generally triggers one added space outside that area only when more than one ADU is proposed, with additional on-street and frequent-transit exceptions. The City's summary page currently conflicts with that adopted text, so obtain written confirmation before designing a stall.
What should I verify before buying a Kirkland DADU plan?
Check Kirkland GIS, then confirm the zone, current survey, FAR and lot coverage, structure position, regulated trees, critical areas, drainage, utility routes, fire access, frontage work, and fees. ADUs over 800 square feet can face impact fees for complete applications received on or after July 1, 2026.
Official sources: KZC 115.07: accessory dwelling units · Kirkland Ordinance O-4905 · Kirkland middle-housing and ADU adoption · KZC 115.42: floor area ratio · KZC 115.90: lot coverage · Kirkland preapproved DADU plans · Kirkland ADU permitting process · Kirkland building and fire-code scenarios · Kirkland ADU regulations · Kirkland GIS maps · Kirkland planning FAQ and tree resources · Kirkland 2025 Critical Areas Ordinance update · Kirkland 2026 fee-change notice
What is allowed on one lot
KZC 115.07 allows two ADUs with a single-family dwelling: two attached, two detached, or one of each. A DADU is a separate building without a common roof to the principal dwelling or attached ADU. A Residential-L shoreline lot is limited to one ADU, and shoreline placement and ownership rules apply.
- Two attached or internal ADUs.
- One attached and one detached ADU.
- Two separate DADUs or two DADUs attached to one another, with different building/fire permit scenarios.
- Conversion of a permitted existing structure, including a detached garage, without curing qualifying setback or lot-coverage nonconformity when it is not increased.
Official sources: KZC 115.07: accessory dwelling units · Kirkland Ordinance O-4905 · Kirkland middle-housing and ADU adoption
How much room the property may have for an ADU
- Maximum size
- Each ADU may contain up to 1,200 square feet of gross floor area. The Director may approve more when an attached ADU is entirely within existing gross floor area on one floor. Areas below five feet of ceiling height, uncovered rooftop decks and at-grade patios, and up to 200 square feet total of specified exterior elements are excluded under the current calculation rules.
- Height
- A new DADU uses the underlying zone's height limit and current grade/height method. Ordinance O-4905 removed ADUs from KZC 115.08's ordinary accessory-structure height and size limits, including the former relationship-to-primary-building cap. Preapproved-plan marketing and older summaries do not replace the parcel's current zone calculation; sloped lots require particular care.
- Setbacks
- The underlying single-family zone supplies the base front, side and rear yards. Without an alley, a DADU may project as close as five feet from the rear line when the portion in the rear yard stays at or below 15 feet above existing grade. With an alley, it may locate within five feet subject to eave and sight-distance rules. Historic-preservation-subdivision and shoreline placement requirements can override the simple backyard model.
- FAR, lot coverage, or impervious area
- The underlying zone supplies numeric FAR and lot-coverage limits. DADU area generally counts in FAR, but the first 500 square feet on a lot below 8,500 square feet or 800 square feet on a larger lot can be excluded when the DADU is more than 10 feet behind or separated from the main structure. Qualifying pre-March 6, 2007 accessory structures have a separate exclusion path.
Official sources: KZC 115.07: accessory dwelling units · KZC 115.42: floor area ratio · KZC 115.90: lot coverage · Kirkland Ordinance O-4905
Parking, occupancy, renting, and separate sale
- Parking
- The controlling 2025 ordinance requires no ADU parking within a half-mile of major transit. Outside that area, the ADU subsection requires one total added space only when more than one ADU is proposed, and waives it when qualifying on-street parking is available within 600 feet or frequent transit meets the stated condition. This conflicts with the current City webpage's statement that a first ADU needs one space; obtain written City confirmation and cite the ordinance.
- Owner occupancy
- No owner-occupancy requirement applies.
- Short-term rental
- Long- or short-term rental requires a Kirkland business license. The City states that a short-term rental must be on an owner-occupied property and registered under the current rental program.
- Separate sale
- Kirkland allows segregated ownership. One or more ADUs, except stacked ADUs, may use the current unit-lot subdivision path. Shoreline Residential-L prohibits separate ownership; shoreline M/H has additional permit and pedestrian-path requirements.
Official sources: Kirkland Ordinance O-4905 · Kirkland moving-in and rental guidance
Utilities, fire access, and the permit path
All ADU applications route through Public Works and MyBuildingPermit. Water meter/service, side sewer, King County wastewater capacity charge, one-curb-cut rules, drainage, frontage, turnaround and fire access must be evaluated. Permit and sprinkler paths differ materially among an attached ADU, separate DADU, two DADUs, or units attached to each other.
- Confirm the exact base zone, shoreline environment, historic-subdivision status, legal structures, transit conditions, title and existing units.
- Apply the current zone's setbacks, height, lot coverage and FAR together with the ADU rear/alley and partial-FAR-exclusion conditions.
- Select the attached/detached configuration early because it determines number of building permits, residential-code occupancy, imaginary property lines, fire separation, water/sprinkler design and unit-lot options.
- Submit through MyBuildingPermit with the site plan, survey, supplemental building form, registration/covenant, plumbing worksheet and all applicable geotechnical, tree, drainage, demolition, rodent and fire documents.
- Confirm fees using the complete-application date; applications received on or after July 1, 2026 can owe park, fire and transportation impact fees when the ADU exceeds 800 square feet.
Official sources: Kirkland ADU permitting process · Kirkland building and fire-code scenarios · Kirkland 2026 fee-change notice
Rules that can change the answer for one property
A citywide ADU allowance does not prove that a detached unit fits on a particular lot. Resolve these items before buying plans or fixing the DADU location.
- Residential-L shoreline sites are limited to one ADU, and detached units must sit landward of the principal house in the shoreline environments specified by code.
- The parking ordinance and the City's summary webpage conflict; use the adopted ordinance and obtain a written interpretation before designing a required stall.
- The current fee notice supersedes older toolkit language claiming categorical ADU impact-fee exemptions.
- The partial DADU FAR exclusion depends on lot area plus physical location/separation; it is not automatic for every detached unit.
- Significant and off-site tree protection, wetlands, streams, lakes, flood areas, geologic hazards, access, turnaround, side sewer and frontage improvements can control feasibility.
Official sources: KZC 115.07: accessory dwelling units · KZC 115.42: floor area ratio · KZC 115.90: lot coverage · Kirkland planning FAQ and tree resources · Kirkland 2025 Critical Areas Ordinance update · Kirkland Ordinance O-4905
Address-level ADU feasibility
What to check before assuming a detached ADU will fit
Kirkland's DADU test uses the exact zone table, shoreline environment, lot area, structure separation and rear position to calculate FAR, yards, height and coverage. Configuration then drives fire, utility, permit and ownership pathways.
Confirm the address is actually governed by Kirkland and select the correct base-zone standards.
Count the principal dwelling, existing legal ADUs, middle-housing units, and the proposed attached or detached configuration.
Use legal lot lines, front/rear designation, alleys, access easements, and existing structures rather than a tax-map rectangle.
Test the ADU against the rules that apply locally: FAR or GFA, building or lot coverage, impervious or hard surface, and landscaping.
Screen critical areas and buffers, shorelines, slopes, flood hazards, significant trees, drainage, and recorded easements.
Verify water, sewer or septic, fire flow, hydrant and apparatus access, power, meters, and trench routes.
The tool should flag the current parking webpage conflict, post-July 1, 2026 impact-fee change, shoreline one-unit limit, sloped-lot height, legal-existing conversions, pre-2007 FAR exception, and frontage/fire-access questions for manual confirmation.
Do not rely on the older rule
Do not rely on two older summaries: the City ADU regulations webpage presently describes one parking space for the first ADU outside transit even though the adopted ordinance only triggers one added space when more than one ADU is proposed; and older toolkit fee language misses the July 1, 2026 impact-fee change for ADUs over 800 square feet.
Primary sources
Official Kirkland and Washington references
These are the sources used for this guide. Check them again before filing because ordinances, fee schedules, and permit forms can change.
What to check first
- 1
Confirm the parcel is inside Kirkland city limits and identify its current zone.
- 2
Map the principal home, lot lines, easements, trees, utilities, driveway, critical areas, and buffers on one current survey.
- 3
Test the ADU footprint against setbacks, height, floor-area or coverage limits, hardscape, parking, and construction access.
- 4
Ask the utility providers to confirm water, sewer, power, meter, side-sewer, and capacity requirements before fixing the design.
- 5
Have the city confirm the complete land-use, building, fire, right-of-way, tree, and utility permit list in writing.