Chapter 20.53
ACCESSORY DWELLING UNITS (ADU)
Sections:
20.53.020 Accessory dwelling units (ADU).
20.53.010 Purpose and intent.
The purpose and intent of this chapter is to allow accessory dwelling units within residential zoning districts as designated in the code, while preserving the appearance and character of existing neighborhoods. Accessory dwelling units give homeowners flexibility in establishing separate living quarters adjacent to their homes so that they might provide housing opportunities for elderly or other family members, obtain rental income, provide affordable housing opportunities within the community, or utilize their property more efficiently. [Ord. 1047 § 2, 2023.]
20.53.020 Accessory dwelling units (ADU).
ADUs may be permanently established on a lot in a residential zoning district under the following standards:
A. ADUs must meet all the development requirements of local, state, and federal regulations, including, but not limited to, all requirements of WMC Titles 18 and 20.
B. An ADU shall not exceed 800 square feet of building area, or the following percentages of the principal dwelling’s building area, whichever is less: 40 percent of the principal dwelling’s building area on lots 0.5 acres or less, 60 percent of the principal dwelling’s building area on lots greater than 0.5 acres but less than one acre, and 80 percent of the principal dwelling’s building area on lots one acre or greater. Any garage associated with the principal dwelling is not included in the calculation of building area. Detached accessory dwellings are included in calculating lot coverage. Lot coverage variances shall not be granted for the construction of an accessory dwelling unit.
C. Only one ADU is allowed per lot. The ADU must be located on the same lot as the primary dwelling, even if the lot’s owner owns two or more adjacent lots. An ADU shall not be located on lots that contain a two-family dwelling as per WMC 20.08.250 or multiple-family dwelling as per WMC 20.08.230 and shall not be located on lots that already contain two or more dwellings.
D. ADUs may be no closer to the front lot line than the primary residence as per WMC 20.08.460.
E. ADUs may only be placed in a side or rear yard, except in the case of a new or converted garage with an integrated apartment, which may be in the front yard providing minimum setbacks are met.
F. The building height of an ADU shall not exceed the building height of the principal dwelling as per WMC 20.08.150. A building height variance shall not be granted for construction of a detached accessory dwelling unit.
G. Lots containing an ADU must provide at least two off-street parking spaces as per WMC 20.52.190.
H. ADUs should utilize a common driveway with the primary residence from the adjacent street, unless impractical due to topographic constraints.
I. An ADU may be used as a vacation rental dwelling or a bed and breakfast inn with a conditional use permit obtained in accordance with the requirements of Chapter 20.68 WMC.
J. Mobile homes, travel trailers, and recreational vehicles may not be used as an ADU.
K. Lots containing an ADU may not be subdivided unless the proposed subdivided lots will comply with all minimum lot size, setback, lot coverage, and other requirements in WMC Titles 19 and 20.
L. An ADU shall not have a material adverse impact on adjacent properties, including but not limited to viewsheds, parking, or compatibility (e.g., mass and scale of development).
M. An ADU shall share the principal dwelling’s sewer and septic system where practical, and the system shall be adequately sized and approved by ADEC for two dwelling units.
N. An ADU shall not be constructed on flag lots, or lots accessed by access easements. [Ord. 1047 § 2, 2023.]