Tumwater to take over as lead for regional partnership to simplify ADU permitting

The City of Tumwater is set to take over as the new project lead of a regional partnership that expedites the permitting process for accessory dwelling units (ADUs) in Thurston County.

The Tumwater General Government Committee endorsed an interlocal agreement with Olympia, Lacey and Yelm to transfer leadership of the project from Lacey to Tumwater at a meeting on Wednesday, June 11. 

The partnership allows homeowners in the cities to take advantage of preapproved plans for ADUs, which are secondary, smaller housing units built on the same lot as an existing home. Due to nationwide challenges in meeting housing demands, there’s a growing push for ADUs to help increase the housing supply. 

The committee also endorsed an agreement with the Artisans Group to update the preapproved plans due to new state regulations. 

Tumwater, Olympia and Lacey have been contracting with the Artisans Group, an architecture firm, since 2020 to develop the plans.  

The firm has so far produced four ADU designs, ranging from 480 to 800 square feet, and will be working on a fifth design for a 1,000-square-foot ADU. The firm will also integrate other updates to an energy code. 

House Bill 1337, which was passed by the Washington Legislature in 2023, set the maximum size of ADUs to 1,000 square feet. Prior to the bill, the maximum size for ADUs was 800 feet in Tumwater, and 850 feet in Olympia and Lacey. 

As the new project lead, Tumwater will serve as the primary point of contact with the firm and take responsibility for managing payments. 

The cost to update the plans and add a fifth design is $41,782. The city will pay the upfront cost and will be reimbursed by the other cities. The cities will split the total cost proportionally based on their respective populations. 

The agreement also acknowledges Yelm as a new member of the project. On top of paying its share, Yelm will need to pay $10,000 to purchase the rights of the existing ADU plans. 

The initiative started in 2019 when Lacey hired the firm to initially develop two preapproved ADU plans. Lacey partnered with Olympia and Tumwater in 2020 to share the costs and, in turn, the rights to distribute the preapproved plans. 

With the committee’s endorsement, the two agreements will now be forwarded to the Tumwater City Council for approval at its meeting on June 17.