Seattle City Council Unanimously Approves Legislation that Allows for Construction of More Mother-in-Law Apartments and Backyard Cottages

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Residents, neighborhood groups, developers, and designers alike are now awaiting the Seattle Mayor’s signature. Last week, after a fine-tuned version was submitted, the Seattle City Council voted 8-0 to adopt proposed legislation that will ease restrictions on the construction of accessory dwelling units, commonly referred to as ADUs or mother-in-law apartments, and detached accessory dwelling units, commonly referred to as DADUs or backyard cottages. The City Council rejected several heavily-debated amendments before its unanimous vote, including an amendment requiring a year of ownership before allowing a second ADU or DADU to be built.

In its final form, the legislation eases restrictions on the construction of ADUs and DADUs and limits the size of construction in single-family (SF) zones. More specifically, the legislation:

  • Increases the per lot allowance from one ADU to two ADUs or one ADU and one DADU.
  • Increases the maximum floor area for a DADU from 800 sq. ft. to 1,000 sq. ft.
  • Increases the allowable height for a DADU by 1-2 ft. depending on certain features.
  • Reduces the minimum lot size to have a DADU from 4,000 sq. ft. to 3,200 sq. ft.
  • Eliminates the requirement for each ADU or DADU to have an off-street parking space.
  • Eliminates the requirement for on-site owner occupancy in order to rent out an ADU.
  • Limits the floor-area ratio in SF zones to .5.

The City Council’s vote marks the end of a two-plus year process that began with the City’s Office of Planning and Community Development (OPCD) issuing a Determination of Non-Significance (DNS)­ and finding that the legislation would not have a significant adverse impact upon the environment­. The City of Seattle Hearing Examiner reversed the DNS after a successful appeal by the Queen Anne Community Council, a neighborhood group, and directed the City to submit an Environmental Impact Statement (EIS) addressing the “impacts on existing housing, including the displacement of some populations.” The City then submitted the EIS, which was upheld on appeal, allowing the City Council to move forward with last week’s vote.

Please contact one of Helsell Fetterman’s Land Use and Real Estate attorneys with any questions or if you would like to learn more about the new legislation.


About the Authors

David Tran

David is an associate in the firm's land use and real estate practice groups.

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