ADU Builders in Kirkland, WA (2026)

An ADU builder in Kirkland is a licensed contractor who designs and constructs accessory dwelling units — detached backyard units, garage conversions, attached additions, and junior ADUs (JADUs). Because an ADU is a complete second dwelling, the builder coordinates foundation, framing, plumbing, electrical, and HVAC work and pulls it through Kirkland's permit process and utility connections. Not every general contractor has built one, so the right builder is one with ADU-specific experience in Washington.

What ADU Builders Cost in Kirkland ^[19]^[20]^[21]^[22]

Based on our Kirkland cost data, expect the following ranges from local ADU builders. Quotes for the same scope typically vary 20-40% between contractors, so getting at least three bids is the single best way to control cost.

New Detached ADU (all-in)	$325,000-$550,000
Cost per Sq Ft	$400-$650
Garage Conversion	$100,000-$225,000
Prefab / Modular ADU (installed)	$300,000-$450,000
City Permit & Plan Review	2026 building permit on valuation (KMC Table 3: $1,620 plus $8.22 per $1,000 over $100,000), plan review at 65% of it, a $101 + $0.01/sq ft energy-code fee and a 3.5% technology fee: about $5,700 on a $300,000 detached ADU before plumbing, fire and utility charges. Plan licence up to $1,000.
Impact Fees	Charged since July 1, 2026 on ADUs larger than 800 sq ft (Ordinances O-4901 and O-4904, phased in): park $2.59, transportation $2.26 and fire $0.38 per sq ft of the whole unit. The city's own example is $4,189 for an 801 sq ft ADU; a 1,200 sq ft unit pays about $6,276. ADUs of 800 sq ft or less pay nothing, and there is no school impact fee on an ADU (O-4910). Rates step up again on Jan. 1 and July 1, 2027; RCW 36.70A.681(1)(a) caps ADU impact fees at half the single-family rate, which is where the current rates sit.

For a full line-item breakdown, see our Kirkland ADU cost guide. To confirm what you're allowed to build before you hire, review the Kirkland ADU rules (max detached size: 1,200 sq ft of gross floor area (KZC 115.07(4)), above the 1,000 sq ft floor in RCW 36.70A.681(1)(f). Not counted: area under 5 ft of ceiling, uncovered rooftop decks or at-grade patios, and up to 200 sq ft of other exterior elements. Ordinance 4905 took ADUs out of the KZC 115.08 accessory-structure cap. Floor area ratio still bites: only the first 500 sq ft (lot under 8,500 sq ft) or 800 sq ft (8,500 sq ft and up) of a detached ADU behind the house is exempt from F.A.R. (KZC 115.42(1)(c)-(d)).; owner-occupancy: Not required; RCW 36.70A.681(1)(b) forbids it. An ADU may be segregated in ownership from the house (KZC 115.07(2)) and, except stacked units, placed on its own unit lot through a unit lot subdivision under KMC Title 22 (KZC 115.07(3); Ordinance 4907, June 2025). Exceptions: no separate ownership in the Residential-L shoreline environment; in the M/H shoreline environment it needs a Substantial Development Permit and a pedestrian pathway under KZC 83.420 (City ADU Regulations page).).

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How to Vet an ADU Builder in Kirkland

License: Confirm a current contractor's license in Washington and that it's in good standing. Ask for the license number and verify it with the state board.
ADU-specific experience: Ask how many ADUs they've completed in or near Kirkland and request addresses or photos. ADU permitting and setbacks differ from a kitchen remodel.
Portfolio & references: Get references from recent ADU clients and, if possible, visit a finished unit.
Insurance: Verify general liability and workers' compensation coverage. Ask for a certificate of insurance.
Written, detailed bid: Insist on an itemized, fixed-price or clearly-scoped bid — not a verbal estimate. It should state whether permits (2026 building permit on valuation (KMC Table 3: $1,620 plus $8.22 per $1,000 over $100,000), plan review at 65% of it, a $101 + $0.01/sq ft energy-code fee and a 3.5% technology fee: about $5,700 on a $300,000 detached ADU before plumbing, fire and utility charges. Plan licence up to $1,000.), plan check (Standard building plan review; intake covers the first review and one resubmittal, and each further review is billed at $179 an hour. The portion of a house converted to an ADU must meet current health and safety codes except that legally built habitable space need not meet IBC ceiling heights (KZC 115.07(8)). An ADU created without a finaled building permit needs an ADU inspection before a permit issues (KZC 115.07(9)(a)(3)). A detached unit closer than 10 ft to another dwelling needs a fire-rated wall detail, and fire sprinklers may be required after the Fire Department's fire-flow and access check.), and impact fees (Charged since July 1, 2026 on ADUs larger than 800 sq ft (Ordinances O-4901 and O-4904, phased in): park $2.59, transportation $2.26 and fire $0.38 per sq ft of the whole unit. The city's own example is $4,189 for an 801 sq ft ADU; a 1,200 sq ft unit pays about $6,276. ADUs of 800 sq ft or less pay nothing, and there is no school impact fee on an ADU (O-4910). Rates step up again on Jan. 1 and July 1, 2027; RCW 36.70A.681(1)(a) caps ADU impact fees at half the single-family rate, which is where the current rates sit.) are included.
Permit handling: Confirm they manage Kirkland's permit process ("Apply through MyBuildingPermit.com (Kirkland > Building > New Construction; a pre-approved plan has its own scope line). The building permit carries the ADU Registration Application, an owner affidavit under KZC 115.07(9), a site plan, the Supplemental Building Information Form, a plumbing worksheet, a survey in most cases and a geotechnical report on soft, landslide or seismic soils. The registration covenant is recorded with the King County Recorder; the recording fee is added to the permit and paid before the certificate of occupancy. A separate Planning Official ADU decision ($634 in 2026) is not needed when the ADU is reviewed with the building permit. Fire checks fire flow, hydrant distance and access on every application; Public Works handles utility connections and drainage. State law bars street improvements as a permit condition (RCW 36.70A.681(1)(l)).", typically About 3 months for a standard ADU permit, plus design and construction time (City Planning Your ADU page, 2026). A registered pre-approved DADU that qualifies for expedited review can be approved in as little as a few weeks; shoreline, geohazard and critical-area sites do not qualify.) and who is responsible if revisions are required.
Payment schedule: Avoid large upfront payments. A reasonable schedule ties payments to completed milestones.

Questions to Ask Before You Hire

How many ADUs have you built in Kirkland in the last two years?
Is your bid fixed-price, and what would trigger a change order?
Are permits, plan check, and utility connection fees included?
What's a realistic timeline, including permit review (About 3 months for a standard ADU permit, plus design and construction time (City Planning Your ADU page, 2026). A registered pre-approved DADU that qualifies for expedited review can be approved in as little as a few weeks; shoreline, geohazard and critical-area sites do not qualify.) and construction?
Who is my point of contact and how are delays communicated?
What warranty do you provide on workmanship?
Can you share three recent Washington ADU client references?

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Frequently Asked Questions

How much do ADU builders charge in Kirkland?

ADU builders in Kirkland typically quote $325,000-$550,000 for a new detached unit, or about $400-$650 per square foot, including design, permitting, and construction. A garage conversion runs $100,000-$225,000 and a prefab/modular ADU averages $300,000-$450,000. Add city permit and plan-review fees (2026 building permit on valuation (KMC Table 3: $1,620 plus $8.22 per $1,000 over $100,000), plan review at 65% of it, a $101 + $0.01/sq ft energy-code fee and a 3.5% technology fee: about $5,700 on a $300,000 detached ADU before plumbing, fire and utility charges. Plan licence up to $1,000.) plus impact fees of Charged since July 1, 2026 on ADUs larger than 800 sq ft (Ordinances O-4901 and O-4904, phased in): park $2.59, transportation $2.26 and fire $0.38 per sq ft of the whole unit. The city's own example is $4,189 for an 801 sq ft ADU; a 1,200 sq ft unit pays about $6,276. ADUs of 800 sq ft or less pay nothing, and there is no school impact fee on an ADU (O-4910). Rates step up again on Jan. 1 and July 1, 2027; RCW 36.70A.681(1)(a) caps ADU impact fees at half the single-family rate, which is where the current rates sit.. Quotes for the same scope commonly vary 20-40% between builders, so collect at least three bids.

How do I find a good ADU builder in Kirkland?

Look for a licensed contractor with completed ADU projects in Kirkland specifically — ADUs involve local zoning, setback rules, and utility connections that general remodelers may not have handled. Verify the license, ask for an ADU-specific portfolio and references, confirm they carry liability and workers' comp insurance, and get a written fixed-price or detailed bid. Submit a request below and we'll forward it to local ADU builders serving Kirkland for free quotes.

Do ADU builders in Kirkland handle permits?

Most full-service ADU builders manage the permit process for you. In Kirkland the approval process is "Apply through MyBuildingPermit.com (Kirkland > Building > New Construction; a pre-approved plan has its own scope line). The building permit carries the ADU Registration Application, an owner affidavit under KZC 115.07(9), a site plan, the Supplemental Building Information Form, a plumbing worksheet, a survey in most cases and a geotechnical report on soft, landslide or seismic soils. The registration covenant is recorded with the King County Recorder; the recording fee is added to the permit and paid before the certificate of occupancy. A separate Planning Official ADU decision ($634 in 2026) is not needed when the ADU is reviewed with the building permit. Fire checks fire flow, hydrant distance and access on every application; Public Works handles utility connections and drainage. State law bars street improvements as a permit condition (RCW 36.70A.681(1)(l))." with a typical review timeline of About 3 months for a standard ADU permit, plus design and construction time (City Planning Your ADU page, 2026). A registered pre-approved DADU that qualifies for expedited review can be approved in as little as a few weeks; shoreline, geohazard and critical-area sites do not qualify.. Confirm in writing whether permit fees, plan check (Standard building plan review; intake covers the first review and one resubmittal, and each further review is billed at $179 an hour. The portion of a house converted to an ADU must meet current health and safety codes except that legally built habitable space need not meet IBC ceiling heights (KZC 115.07(8)). An ADU created without a finaled building permit needs an ADU inspection before a permit issues (KZC 115.07(9)(a)(3)). A detached unit closer than 10 ft to another dwelling needs a fire-rated wall detail, and fire sprinklers may be required after the Fire Department's fire-flow and access check.), and impact fees are included in the bid or billed separately.

How long does it take to build an ADU in Kirkland?

Plan for the permit review (About 3 months for a standard ADU permit, plus design and construction time (City Planning Your ADU page, 2026). A registered pre-approved DADU that qualifies for expedited review can be approved in as little as a few weeks; shoreline, geohazard and critical-area sites do not qualify. in Kirkland) plus construction. Most detached ADUs take 4-8 months of construction after permits are issued; garage conversions and prefab units are often faster. Ask each builder for a realistic schedule and what could delay it.

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Build Cost	$325,000-$550,000
Garage Conv.	$100,000-$225,000
Permit Fees	2026 building permit on valuation (KMC Table 3: $1,620 plus $8.22 per $1,000 over $100,000), plan review at 65% of it, a $101 + $0.01/sq ft energy-code fee and a 3.5% technology fee: about $5,700 on a $300,000 detached ADU before plumbing, fire and utility charges. Plan licence up to $1,000.
Timeline	About 3 months for a standard ADU permit, plus design and construction time (City Planning Your ADU page, 2026). A registered pre-approved DADU that qualifies for expedited review can be approved in as little as a few weeks; shoreline, geohazard and critical-area sites do not qualify.
1BR Rent	$2,450-$2,850/mo

What ADU Builders Cost in Kirkland [19][20][21][22]