ADU Rules in Kirkland, Washington

Kirkland (population ~92,000) is an affluent city on the eastern shore of Lake Washington in King County, part of Seattle's Eastside tech corridor. Kirkland features a vibrant waterfront downtown, Google's Kirkland campus, and proximity to Microsoft's world headquarters in adjacent Redmond. The city is one of the most desirable and expensive communities on the Eastside, facing significant housing cost pressures. Washington's statewide ADU reform is a major tool for adding housing on Kirkland's residential lots.

Washington State ADU Law: HB 1337 (2023)

Washington HB 1337 (2023) is the foundational statewide ADU law that applies to Kirkland. Key requirements:

• Cities must allow up to 2 ADUs per lot — one attached/internal + one detached — by right on any lot with a single-family home
• No owner-occupancy requirement permitted
• No ADU-specific impact fees allowed
• Cities may not require ADUs smaller than 1,000 square feet
• State law limits how restrictive local setback, lot coverage, and height standards for ADUs can be

Washington HB 1110 (2023) accompanies HB 1337, requiring Kirkland to allow duplexes and middle housing in residential zones — a significant departure from Kirkland's historically single-family character.

Kirkland is subject to the Washington Growth Management Act (GMA) and has a comprehensive plan with Urban Growth Area designation coordinated with King County.

Kirkland Local ADU Code

Kirkland's Planning and Building Department administers local zoning and permits. Local ADU regulations must comply with HB 1337 and may not be more restrictive than state law allows.

Permitted ADU Types

• Detached ADU: A standalone structure in the rear or side yard, separate from the primary home
• Attached ADU: An addition to the primary dwelling sharing at least one wall
• Internal/Converted ADU: Conversion of existing space — garage, basement, or upper floor — within the primary structure

Lots may have up to 2 ADUs (one attached/internal + one detached) simultaneously.

Size Limits

State law prohibits Kirkland from requiring ADUs smaller than 1,000 square feet. Confirm current maximum size limits with Kirkland's Planning and Building Department for your specific zone.

Setbacks

HB 1337 limits Kirkland's ability to impose setbacks that would effectively block ADU construction. Setback requirements vary by zoning district. Verify current standards before finalizing ADU design.

No Owner-Occupancy Requirement

State law prohibits owner-occupancy mandates. Kirkland cannot require property owners to live on-site to rent an ADU.

Lake Washington Shoreline and Critical Areas

Kirkland's spectacular Lake Washington waterfront is one of its defining features — and a significant regulatory consideration for ADU projects:

• Shoreline Master Program (SMP): Washington's Shoreline Management Act extends shoreline jurisdiction 200 feet inland from Lake Washington's ordinary high water mark. Development within the shoreline jurisdiction requires a Shoreline Substantial Development Permit for projects above threshold levels. Kirkland's SMP governs what can be built near the lake
• Critical Areas Ordinance (CAO): Kirkland's CAO protects salmon-bearing streams (several flow to Lake Washington), wetlands, steep slopes, landslide hazard areas, and seismically hazardous zones. CAO buffers can substantially affect ADU siting
• Totem Lake: The Totem Lake area in north Kirkland has significant wetland systems

Review Kirkland's GIS mapping tools to identify shoreline jurisdiction and CAO constraints before designing an ADU.

Seismic Hazard

Kirkland and the Puget Sound region face significant earthquake risk from the Cascadia Subduction Zone (CSZ). Areas near Lake Washington have soft soils that can be susceptible to liquefaction and slope instability during strong shaking. USGS and Washington DNR seismic hazard maps identify higher-risk zones. ADU foundations on vulnerable soils require geotechnical input. All construction must meet Washington State Building Code seismic requirements.

Permit Process

1. Check your property's zoning, shoreline jurisdiction, and CAO constraints using Kirkland's GIS system
2. Schedule a pre-application conference with Kirkland's Planning Division for waterfront or constrained sites
3. Prepare construction plans meeting Washington State Building Code requirements
4. Submit permit application at kirklandwa.gov/permits or in person at 123 Fifth Avenue
5. Plan review and permit issuance (shoreline permits required for properties in SMP jurisdiction)
6. Construction inspections
7. Final inspection and Certificate of Occupancy

Contact Kirkland Planning and Building: (425) 587-3600 | kirklandwa.gov

Disclaimer: This guide provides general information based on Washington HB 1337 (2023) and Kirkland's municipal code as of April 2026. Zoning regulations change frequently. Always verify current requirements with Kirkland's Planning and Building Department before making development decisions. This is not legal advice.