Aka Granny Flats. These are small dwellings that are either part of the main house or a separate dwelling. They are an important addition to creating more housing availability. Coming soon to Tillamook County!
The American Planning Association has some definitions and guidelines
The Oregon Legislature has just passed a law allowing ADUs in Rural Residential areas of 2 acres or more (i.e.R2 zones). Details have not been established in Tillamook County. But here is a link to info about it before it passed. https://www.jdsupra.com/legalnews/sb-391-authorizing-accessory-dwelling-8282685/
Here’s a link for the 2018-19 Oregon guidelines https://www.oregon.gov/lcd/Publications/ADU_Guidance_updatedSept2019.pdf
Let us know if you can update these details.