A Backyard Cottage or a DADU is a small residential structure sharing the same lot as a house, but self-contained and physically separate from the primary house. In the Seattle Municipal Code (SMC) zoning provision, Backyard Cottages are referred to as “Accessory Dwelling Units, detached.” They are also sometimes referred to as detached accessory dwelling units, granny flats, mother-in-law apartments, and carriage houses. On some lots, a Backyard Cottage may be located in a side yard.
Because of their small scale, Backyard Cottages can create attractive and affordable rental opportunities for Seattle residents without changing the neighborhood or quality of life for other residents. They can provide greater financial flexibility for homeowners by letting them collect rent for a portion of their existing property or help accommodate larger or multi-generational families. Backyard Cottages also offer a new housing type to Seattle that is desirable, quiet, and compatible with other homes in single-family neighborhoods.
Backyard Cottages provide a surprising number of benefits to communities, homeowners, and renters. Although much of the attention given to Backyard Cottages revolves around their potential for increasing the supply of affordable housing opportunities, Backyard Cottages may also help to address other social issues, particularly those relating to housing options for the growing elderly population.
In December 2009 Seattle City Council adopted legislation to allow the construction of backyard cottages on eligible lots in single-family zones throughout the city. Before the December 2009 legislation, Backyard Cottages were permitted only in Southeast Seattle, where they were authorized by legislation in 2006.
If your property is large enough for a Backyard Cottage there are a variety of other issues you will need to think about. Consider the following:
The City of Seattle has specific development standards for Backyard Cottages. These standards are intended to make Backyard Cottages work with the city’s small lots and compact neighborhoods, allowing additional housing that does not seem intrusive in an established neighborhood of single-family homes. You and your design professional will need to review the standards to design your backyard cottage.