Accessory Dwelling Units

The City recently adopted Ordinance 3963-23 expanding the availability of Accessory Dwelling Units (ADUs) in the city. ADUs are relatively small homes that are secondary to and either attached to or detached from a principal building on a lot. ADUs provide important housing options, which are more likely to be affordable, in city neighborhoods at a small scale. ADUs provide an income stream for homeowners, housing choices for a variety of household types and living arrangements, and work for small-scale developers and builders. Reducing obstacles and simplifying regulations for development of accessory units will help meet city goals, and state requirements, related to housing affordability, variety, ownership, and capacity.

Frequently Asked Questions pertaining to ADUs are detailed below. General resources have also been provided. Counter appointments (virtual or in-person) are encouraged to discuss your project and/or general development questions with on-duty plan reviewers from Planning, Building and Public Works. Counter visits are by appointment only and can be scheduled online. Staff are also available for general development or permitting questions by phone at 425.257.8810 during office/phone hours (M, W, Th 8-12 & 1-3) or via email at  


EMC Title 19: Unified Development Code: Various sections of EMC Title 19 may be applicable to your proposal. Suggested places to start are EMC 19.05.080: Residential Use Table to determine which zones permit ADUS, EMC 19.06: Lots, Setbacks, and Residential Densities for general development/setback requirements, and EMC 19.08.100: Accessory Dwelling Units which outlines general ADU requirements and references other applicable code sections to consider.

Property Report Tool: Resource to determine zoning, proximity to all day transit service, historic overlays, etc. for a specific property. A helpful tutorial to use this tool is also available.

ADU Dashboard: Resource for data, maps, and file numbers for ADUs under review or approved since November 2020.

Permit Services: Establishment of a new dwelling requires permit review and approval. Refer to the Permit Services webpage for permitting instructions, handouts, and resources.

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