Accessory dwelling units provide opportunities for affordable housing, onsite housing for workers and caretakers, housing for extended family members, and rental income for landowners.
—King County, 2000 Comprehensive Plan.

"Accessory dwelling units provide flexible space and a resource that can work for homeowners in a number of ways over time," comments Max Bigby, a housing planner with A Regional Coalition for Housing (ARCH). A nonprofit organization located in King County, Washington, ARCH promotes accessory dwelling units (ADUs) as part of the solution to address the region’s shortage of affordable housing. Currently, more than 300 ADUs exist in the Puget Sound area. These units provide homeowners with an additional source of income or housing for extended family members. Complete with kitchen, bathroom, and sleeping facilities, ADUs are located inside, attached to, or detached from the primary home. Nationwide, developers are also building accessory apartments in new subdivisions.

With Seattle area housing prices and rents soaring, many longtime homeowners could not afford to buy a house in today’s market. ADUs can provide the extra income a family may need to qualify for a mortgage and meet monthly payments, according to ARCH. In King County, ADUs still fulfill their traditional roles—generating extra income to cover rising taxes or maintenance expenses or providing living quarters for an elderly person’s caretaker. When housing needs change, such as when children leave home or the homeowner becomes widowed, homeowners may move into the ADU and rent out the rest of the house. "That’s why ADUs are flexible assets," adds Bigby. "They evolve and adapt to the owner’s needs over time."

Affordable housing advocates like ARCH promote the potential of ADUs to expand the supply of affordable rental units. Not only do these units generally rent for less than an apartment, they do not require public rental or construction subsidies. It costs about 25 to 40 percent less to build an ADU than a comparably sized unit on a separate lot. Because ADUs cost less to build, they generally rent for less than a traditional unit. In addition, ADUs complement smart-growth policies by expanding housing within developed areas.

State law ends restrictions against ADUs. In many communities, zoning laws exclude ADUs from single-family residential areas. In 1994 Washington state passed legislation obligating cities with populations of 20,000 or more to accommodate ADUs in single-family areas, giving municipalities authority to combat efforts to exclude ADUs from residential zones. East King County added 300 ADUs in the 7 years since the law went into effect, according to ARCH. Although Washington communities amended zoning codes and permitting procedures to comply with ADU legislation, little effort was made to publicize the new law to homeowners who might want to add an ADU. ARCH took on the challenge of marketing ADUs to King County homeowners, officials, and other affordable housing groups.

In 1999 ARCH organized seven focus groups representing a cross section of the community to discuss affordable housing issues. The groups outlined three priorities: increasing the number of ADUs, expanding homeownership, and encouraging businesses to become more involved in affordable housing. In response to the focus groups, ARCH recently developed a brochure, Add a Home to Your House, and the ADU Homeowner Packet, which walks the reader through the ADU process, including design, approval, zoning and legal considerations, hiring an architect and contractor, financing, renting the unit, and contact information.

Although the 1994 law ended restrictions against ADUs in single-family neighborhoods, most communities do have restrictions on the units. The homeowner must live in the house, enabling careful tenant screening. In addition, ADUs must still comply with zoning setback and building envelope requirements. Rather than cause problems, as opponents feared, ADUs generally encourage better housing maintenance because homeowners can apply a portion of the rental income to upkeep, asserts ARCH. In some cases, the tenant may perform some maintenance for the homeowner.

ARCH has delineated three major issues that affect ADU resale:

As ADUs become more common in King County, word of mouth is increasing their popularity and acceptance. Someone with an ADU tells a neighbor about its possibilities and advantages, and that person may add a unit in their house or on their property.

For additional information, see: ADUs Homeowner Packet at www.archhousing.org.

Or contact: Max Bigby, Housing Planner, ARCH, 16225 N.E. 87th Street, Suite A-3, Redmond, WA 98052, (425) 861–3677.