Title 17C Land Use Sta ndards
Chapter 17C.300 Accessory Dwelling Units
Section 17C.300.110 Criteria
Maximum Size.
Attached ADU.
Before the esta blishment of an attached ADU the floor area of the principal structure, excluding an attached garage, must be not less than one thousand (1,000) square feet.
The attached ADU must be not more than one thousand (1,000) square feet, excluding any related garage area.
The conversion of an existing interior basement or attic space of a principal structure into an ADU may exceed the maximum floor area for an attached ADU specified in subsection (1)(a) of this subsection.
Detached ADU.
The maximum detached ADU size is subject to building coverage per chapter 17C.300.130 (B)(3) SMC; and
A detached ADU shall not exceed one thousand (1,000) square feet of floor area.
The maximum detached ADU size is subject to the maximum building footprint sta ndards for ADUs in Table 17C.111.205-2 .
Occupancy for Short-Term Rentals.
Where a lot with an ADU also has a Short-Term Rental under chapter 17C.316 SMC , one of the dwelling units on the lot shall be occupied by one or more owners of the property as the owner’s permanent and principal residence. The owner-occupant must occupy the owner-occupied dwelling unit for more than six months of each calendar year. The owner-occupant may not receive rent for the owner-occupied dwelling unit. If a complaint that an owner has violated these requirements is filed, the owner shall:
submit evidence to the director showing good cause, such as a job dislocation, sabbatical leave, education or illness, for waiver of this requirement for up to one year absence from the property. Upon such showing the director may waive the requirement;
re-occupy the structure; or
remove the accessory dwelling unit.
Date Passed: Monday, June 2, 2025
Effective Date: Friday, July 11, 2025
ORD C36696 Section 3