News release from City of Seattle, Seattle City Council
Report prepared for the Seattle City Council
Removing Barriers to Backyard Cottages & Accessory Dwelling Units
Councilmember O’Brien’s bill makes a series of changes to the existing backyard cottage and mother-in-law unit building code. Here is a link to changes. The legislation ( draft) to increase the housing supply by encouraging low-impact housing options that fit within the scale and character of Seattle’s single-family neighborhoods.
Here are a few changes:
- Allowing both a backyard cottage and mother-in-law unit on the same lot, which provides additional housing options while maintaining the character and appearance of the property.
- Increasing the height limit for backyard cottages by 1-2 feet, depending on lot width, which would allow enough livable space to make two-bedroom units more feasible. Setback requirements from property edges would not change.
- Removing the requirement for owners to include an off-street parking space for backyard cottages or mother-in-law unit. Currently, this requirement often requires removal of green space on the property. Feedback found the parking requirement was prohibitive in creating new backyard cottages, as additional parking spaces were either unnecessary or unable to fit on the lot. For single-family lots outside urban villages or urban centers, the one required off-street parking space for a single-family house requirement will still apply.
- If a backyard cottage is only one-story, its floor area may cover up to 60% of the rear yard (currently 40%), creating a large enough livable space for those unable to use stairs. Existing setback requirements from the lot edge would not change.
- Requiring that the property owner live on-site for at least one year after a backyard cottage or mother-in-law unit is created, rather than the current requirement that the owner live on-site at least 6 months out of every year in perpetuity. The requirement prevents speculative developers from acquiring property and building backyard cottages that don’t fit the character of the neighborhood, while allowing the owner future flexibility for those who don’t want, or are unable to continue living on-site.
- Allowing backyard cottages on lots 3,200 square feet or greater in area (currently 4,000 square feet), which would make approximately 7,300 additional parcels eligible to provide this additional housing option.
- Increasing the maximum gross floor area of a backyard cottage to 1,000 square feet (currently 800 square feet), which would provide more livable area and increase the likelihood of two-bedroom backyard cottages to better serve families with children.
- If a backyard cottage is built above a garage, the garage square footage will no longer count toward the maximum floor area, which often results in an unreasonably small living space.