Yes, accessory apartments are allowed in all residential zoning districts and are processed as a Type I land use action per BGMC 17.135. The ADU is required to meet setbacks for the zoning district you live in. See an earlier question to figure out what zone you are in and what your setbacks are. Lastly, the ADU cannot be larger than 40% of the gross floor area of the primary single-family structure (not including garage). The maximum square footage allowed for an ADU is one thousand square feet. If you need help determining size and placement of an ADU, please call the city’s planning department at 360-342-5047.