urban | design.banter :: More Guidelines for ADU's

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This summer we posted a summary on Accessory Dwelling Units (ADU's): a brief explanation, some benefits, and regulations for Seattle and King County. Below we will outline the regulations for the San Juan Islands.

Accessory Dwelling Units (ADU's) have become more popular and acceptable in the past few years. The City of Seattle began allowing for ADU's in all residential zones (it had previously been only some south Seattle neighborhoods) in 2009. San Juan County allows for a limited number of permits for ADU's each year.

An ADU can be attached, as in a basement apartment, or detached, as in a backyard cottage, carriage house, or alley flat. The implementation of ADU's can fulfill many goals of sustainable development, including density, affordable housing, and smaller house sizes. As our urban fabric is "re-knit", neighborhoods can become more dense, creating more demand for services, therefore creating more opportunities for walkable neighborhoods and less dependence on a car.

Truly sustainable development also includes social goals, many of which are also met by integrating ADU's: a way for homeowners to have a separate income stream, a mix of income and ages; the ability to stay in one neighborhood through varying phases of life, therefore creating lasting community: kids can live in a backyard cottage as they start on their career path, elderly parents or relatives can live in smaller spaces that require less upkeep and be close to their children and grandchildren. The term "mixed income" may be worrisome, but from a social standpoint, renting out an ADU can more successful than an absentee landlord renting a house, in that owners are close to the rental unit, tenants are close to their landlord, so each keeps an eye on each other. The Kentlands Development in Maryland (designed by New Urbanism pioneers DPZ)  is a neighborhood that has successfully integrated market rate, large suburban housing with backyard rental units. An often cited example is of a woman who lived in her ADU and rented out her large house in order to save money and pay off her mortgage.

Anna spoke to BUILDERnews magazine about the benefits of building an ADU or guest apartment. See the article, including photos of two of our projects that include these structures here.

Hare House in Friday Harbor, Second Floor Plan: an apartment over an office and garage can be used for family, or rented out for extra income.

San Juan County:

San Juan County defines an ADU as "a living area that is accessory to the principal residence, located on the same lot, and that provides for sleeping quarters, kitchen, and sanitation facilities. An ADU may be internal, attached or detached."

• The distinguishing characteristic signifying an ADU for the county is a kitchen, even without an oven or stove. A guest or mother in law suite with just a bedroom and bathroom may not be subject to the same restrictions.
• An ADU must not exceed 1,000 square feet 
• There is a limit on the number of ADU permits available, so check with county before moving ahead. The number of detached ADU permits in any calendar year shall not exceed 12 percent of the total number of building permits for new principal residences issued for the previous calendar year. 
• In order to reduce impact, ADU's must be located within 100 feet of the principal residence. 
• Urban Growth Areas and Activities centers generally allow ADU's with less restrictions than rural zones
• A detached ADU is not permitted on parcels less than five acres in size in any rural district, 10 acres in size in the agricultural district, and 20 acres in size in the forest district. Visit the Assessor's Site to find out what zone you are in. 
• Within the Town of Friday Harbor, a detached guesthouse is not a permitted
  accessory structure in Single Family Zones. The Hare House, which is in town and includes a guest house, is in a Multifamily Zone.

 Example home plan, the Pearl Cottage, under 1,000 square feet

Our Home Plan Collection has some great floor plans and designs under 1,000 square feet. View the collection for ideas and inspiration-plans can be customized to meet your needs. 

Next Friday, we'll look at regulations for Bellingham, Anacortes, and Island County.