Accessory Dwelling Unit (ADU)

Notice of Adoption:

  • December 15, 2020 -  The Board of County Commissioners adopted the Rural Accessory Dwelling Unit (ADU) ordinance at their regularly scheduled meeting on December 15, 2020 at 2pm. The Building Development Center has created a new ADU webpage containing more information and links to all ADU ordinances administered by Thurston County.  If you have questions, please contact 

Project Description

Thurston County is considering an amendment to code language to allow a small, separate living unit on the same lot as a single-family home in rural, unincorporated parts of the County.  Design standards for these accessory dwelling units (ADUs) are being explored as part of the Development Code Docket.  

An Accessory Dwelling Unit (ADU) is a small, separate living unit built on the same lot as a single-family home. Traditionally, ADUs can be an addition to a single-family home, a conversion of a basement or attached garage, or a freestanding "detached" structure. An ADU has all the basic facilities for day-to-day living, such as a kitchen, sleeping area, and bathroom. As the term "accessory" implies, ADUs are smaller in size, use and prominence than the main residence on the lot.

ADU Types‚Äč