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 [9]
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) | $250,000-$450,000 |
| Cost per Sq Ft | $300-$500 |
| Garage Conversion | $120,000-$250,000 |
| Prefab / Modular ADU (installed) | $180,000-$350,000 |
| City Permit & Plan Review | Confirm current permit and plan review amounts with Kirkland Planning and Building at 425-587-3600 — no ADU fee schedule is published on the city's ADU Toolkit pages. If you use a pre-approved plan, budget separately for licensing it from the designer, which the city puts at up to $1,000 |
| Impact Fees | Capped by state law at 50 percent of the impact fees that would be imposed on the principal unit (RCW 36.70A.681(1)(a)). Kirkland does not publish an ADU-specific figure on its ADU pages — confirm the current park and school impact fee amounts with Kirkland Planning and Building at 425-587-3600, and cite the 50 percent cap if the quote looks high |
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 (Kirkland Zoning Code 115.07(4)) — 200 sq ft above the 1,000 sq ft floor state law guarantees (RCW 36.70A.681(1)(f)). Area with less than five feet of ceiling height, uncovered rooftop decks and at-grade patios, and up to 200 sq ft of other covered and uncovered exterior elements do not count. The practical catch is floor area ratio: only the first 500 sq ft of a detached ADU on a lot under 8,500 sq ft, or the first 800 sq ft on a lot of 8,500 sq ft or more, is exempt from F.A.R., and then only when the structure sits behind the main house (KZC 115.42). If F.A.R. would push your ADU below 1,000 sq ft, raise RCW 36.70A.681(1)(f) with the planner; owner-occupancy: Not required, and Kirkland could not require it if it wanted to — "the city or county may not require the owner of a lot on which there is an accessory dwelling unit to reside in or occupy the accessory dwelling unit or another housing unit on the same lot" (RCW 36.70A.681(1)(b)). Kirkland goes further: an ADU may be segregated in ownership from the single-family dwelling unit, and one or more ADUs other than stacked units may be subdivided within a unit lot subdivision (Kirkland Zoning Code 115.07(2)-(3)). The city's ADU Regulations page notes an exception for properties in the Residential-L Shoreline Environment).
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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 (Confirm current permit and plan review amounts with Kirkland Planning and Building at 425-587-3600 — no ADU fee schedule is published on the city's ADU Toolkit pages. If you use a pre-approved plan, budget separately for licensing it from the designer, which the city puts at up to $1,000), plan check (Standard building plan review. The portion of a single-family dwelling in which an attached ADU is proposed must meet all applicable health and safety codes, except that space legally constructed as habitable space need not meet current International Building Code ceiling height requirements (Kirkland Zoning Code 115.07(8)). If an ADU was created without a finaled building permit, an ADU inspection is required before an ADU permit will issue (KZC 115.07(9)(a)(3)). Applicants planning two attached ADUs are told to call Planning and Building at 425-587-3600 for extra Building Code help), and impact fees (Capped by state law at 50 percent of the impact fees that would be imposed on the principal unit (RCW 36.70A.681(1)(a)). Kirkland does not publish an ADU-specific figure on its ADU pages — confirm the current park and school impact fee amounts with Kirkland Planning and Building at 425-587-3600, and cite the 50 percent cap if the quote looks high) are included.
- Permit handling: Confirm they manage Kirkland's permit process ("Apply for an Accessory Dwelling Unit permit with the Kirkland Planning and Building Department, including an affidavit signed by the property owner agreeing to the requirements of KZC 115.07. Where the improvements do not require a building permit, a registration form is filed instead. Either way the owner files a property covenant with the City for recording with the King County Recorder's Office, noting the presence of the ADU; the covenant runs with the land as long as the ADU is maintained (Kirkland Zoning Code 115.07(9)(a)). A decision of the Planning Official is appealable under Chapter 145 KZC. State law bars the city from requiring public street improvements as a condition of permitting an ADU (RCW 36.70A.681(1)(l))", typically Roughly 3 months for a standard ADU permit, with additional time for design and construction; a pre-approved DADU application takes less — the city says as little as a few weeks (City of Kirkland, Planning Your ADU and Explore Kirkland's Pre-Approved Plans)) 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 (Roughly 3 months for a standard ADU permit, with additional time for design and construction; a pre-approved DADU application takes less — the city says as little as a few weeks (City of Kirkland, Planning Your ADU and Explore Kirkland's Pre-Approved Plans)) 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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