Backyard Cottages

Seeking to promote both affordable housing and a gentle increase in density in single-family neighborhoods, the City Council in 2006 decided to allow what are officially called “detached accessory dwelling units” (DADUs) in a limited part of the city.

This pilot program in Southeast Seattle allowed backyard cottages only east of Interstate 5 and south of Interstate 90. The program proved satisfactory to the City Council and it made construction of backyard cottages legal throughout the city in December 2009.

The city’s backyard-cottage legislation includes a number of restrictions: Cottages can be no larger than 800 square feet, including any garage or storage area, and the property owner must live in either the main house or cottage.

The lot must be in a single-family residence zone and be at least 4,000 square feet in size. As is required for all single-family houses in Seattle, the total area of built structures can cover no more than 35 percent of the lot, and at least one off-street parking place must be available to the occupants of the original home, plus at least one more dedicated for the cottage residents.

Basements are allowed, and any area at least 4 feet below grade doesn’t count toward the 800-square-foot size limit. Most neighbors view backyard cottages as favorable, and in some cases, unnoticeable additions to their neighborhoods; there are some neighborhoods, such as Laurelhurst, that have been active in fighting this change.