ADU Rules in Kirkland

Kirkland allows two accessory dwelling units with each single-family home, in any combination of attached and detached, at up to 1,200 square feet each. ADUs follow the same height, setback and lot coverage rules as the house, most lots need little or no added parking, and a detached unit can be owned separately from the main home.

Kirkland reached most of these rules years before the state required them, then adjusted its code again in 2025. Below is what the Kirkland Zoning Code says today, where the details trip people up, and how the process works at the city. For a side-by-side view of neighboring cities, see our summary of how Puget Sound cities adopted HB 1337.

An Early Reformer That Updated Again in 2025

Kirkland rewrote its ADU section in 2020, well ahead of HB 1337. That update allowed two ADUs per house, including two detached units, dropped the owner-occupancy requirement, set the 1,200-square-foot limit and waived parking for a lot’s first ADU.

Ordinance O-4905, adopted on June 17, 2025, brought the code in line with the state law, and a second 2025 ordinance made further edits to the same section. Comparing the earlier text of Kirkland Zoning Code 115.07 with the current version shows the main changes:

Height no longer has a separate accessory cap; the older rule that kept a detached unit within 15 feet of the main house’s roof peak is gone.

Parking is now waived outright for lots close to major transit.

Converted structures, such as detached garages, are exempt from current setback and lot coverage rules as long as existing nonconformities do not grow.

ADUs can now be split off through a unit lot subdivision, not just held in separate ownership.

Two Units, Any Combination, With a Shoreline Exception

The code allows one attached ADU and one detached ADU, or two of either type, per single-family dwelling. Two basement or above-garage units, or two backyard cottages, are all possible where the lot has room. Our explainer on how many ADUs one lot can hold in Washington covers the statewide rule behind this.

Waterfront properties are the exception. The city’s ADU regulations page notes that lots in the Residential-L Shoreline Environment, found along the Lake Washington shore in neighborhoods such as Houghton, Lakeview and Market, are limited to one ADU, and that an ADU there cannot be segregated in ownership. If your lot touches the lake, confirm the shoreline designation before you design.

What Counts Toward the 1,200 Square Feet

The limit is 1,200 square feet of gross floor area per ADU. Kirkland leaves several areas out of the calculation: space with a ceiling height under 5 feet, uncovered rooftop decks and patios, and up to 200 square feet of covered or uncovered exterior elements such as porches.

For an attached ADU created entirely within existing floor area on one level of the house, the Planning and Building Director may allow more than 1,200 square feet. That helps owners of large daylight basements avoid walling off usable rooms just to hit a number.

Height Follows the House in RS and RSX Zones

Kirkland does not set a special height limit for ADUs. A detached unit uses the height allowed for a single-family home in its zone. In RS zones the limit is 25 feet above average building elevation, and in RSX zones it is 30 feet. Average building elevation is a weighted average of the ground around the building, so slope affects how much height you actually get.

Twenty-five feet comfortably fits a two-story cottage or a unit above a garage, but a steep lot can eat into that. Check your zone on the city’s zoning map early, since the RS and RSX difference changes what a second story can look like.

Yards, Coverage and Floor Area on a Kirkland Lot

Because ADUs follow single-family standards, the numbers for a detached house apply. In the RS and RSX zones that means a 20-foot front yard, 5-foot side yards with at least 15 feet combined, a 10-foot rear yard and lot coverage of up to 50 percent.

Floor area ratio is the limit that most often decides what fits. Kirkland’s low-density zones cap total floor area as a share of lot size, and the ADU counts toward it. On a modest lot with a newer, larger house, an attached unit carved from existing space may be the only route that stays under the cap. Older close-in neighborhoods with smaller lots tend to hit this limit first, while hillside lots with views more often run into height and grading questions instead.

Garage owners have an advantage. Converting an existing detached garage does not have to meet today’s setbacks or coverage, provided the work does not increase the nonconformity. Our guide to turning a garage into an ADU covers the design side.

Kirkland’s Layered Parking Rule

Kirkland’s parking rule has several layers, and the code text is more lenient than many summaries suggest:

Near frequent transit, meaning within a half-mile walk of a major transit stop, Kirkland asks for no parking whatsoever.

Elsewhere, a lot with a single ADU needs no added space.

A lot with more than one ADU needs one off-street space in total, unless on-street parking is available within 600 feet or the property is within half a mile of transit service running every 15 minutes during commute hours.

The city’s toolkit page describes the rule in slightly different words, so confirm how it applies to your address with planning staff before you give up yard space for a parking pad.

Separate Ownership and Unit Lot Subdivision

An ADU in Kirkland may be held in separate ownership from the house. One or more ADUs, except stacked units, may also be divided onto their own unit lots through a unit lot subdivision under Title 22 of the municipal code. That gives owners a path to sell a cottage on its own, though it involves surveying, legal work and city review well beyond the building permit.

The 800-Square-Foot Fee Threshold

Size affects fees. Under the municipal code, a legal ADU of 800 square feet or less is exempt from Kirkland’s transportation impact fee. The city’s current impact fee schedule lists ADUs larger than 800 square feet as a separate category for transportation, park and fire fees, measured by square footage. School impact fees follow their own schedule. Separately, Washington law limits any ADU impact fee to 50 percent of the fee charged for the principal home.

If a unit is close to 800 square feet, it is worth checking the current schedule before you finalize the floor plan.

Applying Through MyBuildingPermit

ADU applications go to Kirkland’s Planning and Building Department through the MyBuildingPermit online portal, which is also used to track review and schedule inspections. For a detached unit built from one of the city’s pre-approved plans, the submittal list includes a site plan with the plan’s registration ID, an ADU registration application, a plumbing worksheet and, in most cases, a survey. A geotechnical report, rodent abatement letter, fire sprinkler permit or demolition permit is added when the site or scope calls for it.

Kirkland’s pre-approved DADU plans come from several local architects and are designed to shorten review compared with a custom design. Our ADU timeline guide shows where permit review sits in the overall schedule.

How Kirkland Compares With Bellevue Next Door

The two cities now allow the same number of ADUs and the same 1,200-square-foot limit, but they diverge in the details. Kirkland applies house height to a backyard unit, while Bellevue caps detached ADUs at 24 feet. Kirkland waives parking for a lot’s first ADU outside transit areas, while Bellevue ties parking to units of 1,000 square feet or more. Our guide to Bellevue’s ADU code covers that city’s rules in full. If you are ready to look at your own property, the Kirkland design-build team at United Signature can walk the lot with you and map out the options.

FAQ

Did Kirkland allow two backyard cottages before the state law?

Yes. Kirkland’s 2020 code already allowed two ADUs of either type per house, so two detached units were possible before HB 1337 took effect.

Can a Kirkland ADU be taller than the main house?

It can, as long as it stays within the zone’s height limit. The older rule that tied a detached ADU to the main house’s roof peak no longer appears in the code.

Are decks and porches counted in Kirkland’s ADU size limit?

Uncovered rooftop decks and patios are excluded, along with up to 200 square feet of covered or uncovered exterior elements. Larger covered areas can count, so the floor plan should show the calculation.

Is my Lake Washington waterfront lot eligible for two ADUs in Kirkland?

It depends on the lot’s shoreline designation. According to the city, lots in the Residential-L Shoreline Environment are limited to one ADU, and that unit cannot be owned separately.

Do I need a survey for a Kirkland ADU permit?

In most cases, yes. The city’s submittal list for detached ADUs includes a survey, which also helps confirm yards, coverage and floor area before the design is final.