Friday, December 10, 2010

urban | design.banter :: More Guidelines for ADU's-North Puget Sound

Each Friday we bring you  urban | design.banter 
:: infill | re-knitting our urban fabric | cohousing | keeping small towns from becoming suburbs :: why shouldn't where you live be somewhere you would want to visit?

In this series, we are giving you a brief overview of what some jurisdictions allow. Not all of them allow Accessory Dwelling Units (ADU's) in single family zones. If you would like to build one, or just advocate for the cause of affordable housing, mixed income neighborhoods, density, accountable tenant-landlord relationships (landlord lives in the house, so he is not absentee, renter lives right there, so is held accountable), and allowing families to provide shelter for other family members on their land, talk to your local government. Many jurisdictions are realizing that allowing ADU's can help us reach many of the goals mentioned above and are changing their zoning codes to allow them. Here are some results of a questionnaire for the City of Seattle from our first article on ADU's:

Among those aware of a backyard cottage in their neighborhood:
• 71% said that the backyard cottage in their neighborhood fit in with the surrounding homes.
• 84% noticed no impacts on parking or traffic directly related to the backyard cottage.
• 83% were supportive or strongly supportive of backyard cottage policy.

  • Medium Density Residential zones: "caretaker's cottage" up to 140 SF. May need to fight for ADU. Attached ADU would be no problem in this zone as duplexes are allowed.
  • Single Family Residential zones:  No ADU's allowed currently


The city allows attached ADUs only (for instance, in a basement, as a flat on the second floor, or in addition), unless you want to renovate and existing detached unit. Here are some of their guidelines:
  • The floor area of ADU must not exceed 40% of the area of the primary residence, with a maximum area of 800 square feet (for both attached and detached), two bedrooms, three people
  • Only one entrance can be visible from the street, and any off street parking displaced by the new building must be replaced. Parking for the ADU should preferably be off the alley, if possible.
  • One of the building must be owner occupied. 
  • More information here
  • Here is some information on the code requirements in regard to construction, including creating a one hour fire separation between the units
Island County (Oak Harbor, Camano, Whidbey Island)
  • ADU's (in this code referred to as detached accessory Dwelling Unit or Guest Cottage) are allowed in most zones (Rural Residential zones must have a lot size of at least 1 acre). 
  • Must not exceed 1,000 square feet or 20% of floor area of the primary residence, whichever is larger (Max 2,500 square feet)
  • ADU and primary residence must share a driveway
  • Thirty five ADU's may be permitted each year in the county
Let us know if you are curious about ADU's and your city or county has not been covered.

Other blog entries about ADU's: ADU 101 with rules for Seattle/King County and San Juan Islands

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