ADUs Decisions in Snohomish County

An Accessory Dwelling Unit (ADU) is a secondary housing unit located on the same parcel as a primary single-family residence. ADUs go by many names - granny flats, in-law suites, backyard cottages, garage apartments, or casitas - but they all share the common characteristic of being smaller, subordinate residential units that share a lot with the main house. ZoneWire tracks adus activity across Snohomish County, WA public meetings.

ZoneWire monitors Snohomish County, WA planning and council meetings, transcribes them, and flags adus activity. As of the latest update we have analyzed 0 meetings and detected 0 adus mentions.

Tracking adus in Snohomish County surfaces zoning and development signals early, so developers, investors, and brokers can evaluate parcels and approvals before they reach the broader market.

Zoning in unincorporated Snohomish County is governed by Title 30 of the Snohomish County Code, the Unified Development Code. Title 30 lists all zoning designations in Table 30.21.020 and describes the intent of each zone in SCC 30.21.025. It contains three "Use Matrix" tables (SCC 30.22.100, .110, and .120) for urban zones, rural and resource zones, and other zones, which identify the permitted, conditionally permitted, and prohibited uses for each zone. Dimensional standards such as minimum lot area, setbacks, height, and lot coverage are set out in the "Bulk Matrix" at SCC 30.23.030 with reference notes in SCC 30.23.040.

Property owners can pursue a rezone in two ways: a quasi-judicial (Type 2) rezone, used when the proposal is consistent with the Comprehensive Plan, or a legislative rezone through the docketing process when the change may be inconsistent with the plan (allowing a concurrent Future Land Use Map amendment). For quasi-judicial rezones, the Department of Planning and Development Services (PDS) reviews the application, provides public notice with a 14-day comment period, and transmits a recommendation to the Snohomish County Hearing Examiner, who is required to hold an open-record public hearing. The Hearing Examiner may approve, approve with conditions, remand for further review, or deny the request. Legislative rezones are reviewed by the Planning Commission and County Council through the docketing process.

R-5 is the Rural-5 Acre zone, intended to maintain rural character in areas that lack urban services. It is a rural residential designation established under Title 30, with its intent described in SCC 30.21.025 and its dimensional standards (including minimum lot area) set in the Bulk Matrix at SCC 30.23.030. As one indicator of the zone's density, detached accessory dwelling units are prohibited on R-5 lots less than 5 acres (200,000 square feet) in size. For exact lot-size and setback figures, property owners are directed to consult the Bulk Matrix and reference notes in SCC 30.23.040 or contact PDS.

Critical areas are regulated under Snohomish County Code Chapter 30.62A, adopted pursuant to the Growth Management Act to designate and protect wetlands, fish and wildlife habitat conservation areas, and their buffers. Required buffer widths are established in SCC 30.62A.320 (Table 2a for streams, lakes, and marine waters; Table 2b for wetlands). Development activity requiring a project permit in a critical area or its buffer may require a critical area study prepared by a qualified professional, and no new effective impervious surfaces are allowed within the buffer of streams, wetlands, lakes, or marine waters.

The Comprehensive Plan is the county's long-range blueprint for growth, required and periodically updated under Washington's Growth Management Act (GMA). The most recent update, the 2024 Comprehensive Plan Update, was adopted in December 2024 and covers a 20-year planning horizon through 2044. The GMA framework directs growth into designated Urban Growth Areas (UGAs) where urban services and facilities are provided, and comprehensive plan updates undergo environmental review through the State Environmental Policy Act (SEPA).

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