It’s about to get easier to build a backyard cottage in Seattle

by | Jul 14, 2019

On Monday, July 1, the Seattle City Council voted unanimously to ease regulations on building backyard cottages and accessory dwelling units (ADUs), also known as in-law apartments. According to the bill’s sponsor, District 6 councilmember Mike O’brien, the objective of the legislation was to “create more housing choices in single-family zones.”

While backyard cottages have been allowed in all parts of Seattle since 2009, only 221 had been built as of 2016. The new rules will make it easier for property owners to build backyard cottages and ADUs. Advocates hope that by increasing supply, housing will become more affordable in Seattle.

Here are some of the most significant updates of the new rules:

  • Reduces the lot size requirement to build a backyard cottage from 4,000 square feet to 3,200 square feet.
  • Increases the maximum size of the backyard cottage from 800 square feet to 1,000 square feet, not counting any parking or storage space.
  • Removes the requirement that the owner must occupy the property.
  • Dedicated off-street parking spaces for cottages and ADUs are no longer required.
  • Increases the height limit of backyard cottages by 1 to 3 feet.
  • The maximum number of accessory units allowed on a lot gets increased from one to two—either a backyard cottage and an ADU inside the main home, or two ADUs inside the main home.

In addition, the new legislation included a so called “McMansion” ban, which added a new floor-area-ratio (FAR) limit of 0.5. This means that the maximum square footage of a new home built on a 6,000-square-foot lot would be 3,000 square feet. Backyard cottages and ADUs would not be included in this limit, which reduces the incentive to tear down a modestly sized home and replace it with a jumbo-size single-family home. Instead, advocates hope the new rules will encourage homeowners to add a backyard cottage or basement apartment.

Backyard cottages and ADUs can earn homeowners rental income or serve as extra space for family and friends.

The new rules are expected to reduce the number of teardowns and increase the number of new housing units added to the city’s housing supply. The city’s Environmental Impact Statement (EIS) estimates that over the next 10 years the new regulations will spare 450 homes from the bulldozer and help add 4,430 new accessory units, which is 2,460 more than would have been built under the old rules.

An earlier version of the legislation was first proposed by Councilmember O’Brien in late 2015. Its progress was stalled by two legal appeals, which were eventually dismissed.

Mayor Durkan signed the legislation last Tuesday, and the new rules will go into effect August 8, 2019. The FAR regulation has a delayed effective date of March 1, 2020. In addition, Mayor Durkan signed an executive order to help homeowners with the design and permitting process, offer low-interest ADU financing through the Office of Housing’s Home Repair Loan Program, and convene a workgroup to assess the effectiveness of the regulatory changes within three years.

Eric Thomas is marketing manager for CRD Design Build, a Phinney Neighborhood Association business member. CRD has provided residential remodeling services to the Seattle community for nearly 40 years. Eric gathers news and information about the topic at the Ultimate Guide to Seattle Backyard Cottages.

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