The purpose of this chapter is to:

(1) Add affordable units to existing housing and make housing units available to moderate-income residents who might otherwise have difficulty finding homes within the town.

(2) Protect neighborhood stability, property values and the single-family residential appearance of the neighborhood by ensuring that accessory dwelling units (“ADUs”) are constructed according to applicable code provisions.

(3) Promote the development of additional housing options in residential neighborhoods that are appropriate for people at a variety of stages of their lives. [Ord. 887 § 2 (Exh. 1), 2025]

The town planner shall have the authority to approve ADUs which are consistent with the regulations and provisions herein. [Ord. 887 § 2 (Exh. 1), 2025]

(1) Allowed Zoning. ADUs may be allowed in any zone on a lot where a dwelling unit exists as a permitted use if they comply with the requirements listed in this chapter. Two ADUs are permitted on all lots that are located in all zoning districts that allow for dwelling units. ADUs can be categorized as either attached or detached. An ADU may be created by any one or combination of the following methods:

(a) A separate unit within an existing home (such as in an attic or basement); or

(b) An addition to the home (such as a separate apartment unit with a separate entrance); or

(c) In a separate detached structure on the lot (such as but not limited to a new or converted garage).

(2) Sale/Conveyance. The town shall not prohibit the sale or other conveyance of a condominium unit independently of a principal unit solely on the grounds that the condominium unit was originally built as an ADU.

(3) Permitted Size. An ADU shall not be less than 400 square feet nor greater than 1,000 square feet in area.

(a) The ADU sizing is calculated per the 2021 (or currently adopted edition) International Building Code which is the inside perimeter of the exterior walls of the building under consideration, exclusive of vent shafts and courts, without deduction for corridors, stairways, ramps, closets, the thickness of interior walls, columns or other features. Areas that are less than five feet in height are not counted in the ADU square footage. Additionally, garages are not counted in the ADU square footage. [Ord. 887 § 2 (Exh. 1), 2025]

(1) An ADU, and any accessory structures for the ADU such as but not limited to garages, carports, or workshops, shall comply with the underlying zoning district for the dwelling unit located on site, including height, setbacks, floor area, accessory buildings and lot coverage, except as provided in this section.

(2) One on-site parking stall is required for an ADU. However, no parking is required when either improved public street parking is available on at least one side of the lot whereon the ADU is proposed, or the ADU is within one-half mile walking distance to a major transit route. If the lot abuts an alley or private access easement, parking shall be accessed from the alley or private access easement except when the town planner determines that such access is environmentally constrained.

(3) For detached ADUs, a minimum of 10 feet separation from the existing dwelling unit is required.

(4) Any utility lines being installed or altered must have their connections inspected as part of the building permit process.

(5) Attached ADUs can use the water meter and side sewer that was permitted for the existing dwelling unit. However, all detached ADUs shall have their own water meter and side sewer connection. If fire sprinklers are required, the property owner shall install a backflow prevention device behind the water meter.

(6) All water and sewer system charges shall apply for any new connection and/or modifications to the existing water and sewer system(s) for an ADU.

(7) ADUs are not permitted on lots that are not connected to and served by public water and sewer.

(8) Existing structures, including but not limited to detached garages, may be converted into ADUs even if they violate current code requirements for setbacks or lot coverage; provided, that the existing structure(s) proposed to be converted into an ADU may be required to be brought into conformance with current building and fire code requirements. Existing detached structures proposed to be converted to ADUs shall not be located across property lines or within the right-of-way.

(9) Addressing of the existing dwelling unit shall be changed to identify the existing dwelling unit as “Unit A” and the new ADU as “Unit B” prior to issuance of a certificate of occupancy (CO).

(10) An approved building permit is required to construct an ADU in the town. The building permit must comply with the town’s adopted building code, fire code, zoning code, critical area regulations, environmental regulations, and stormwater regulations adopted at time permitting is sought.

(11) When property corners are not known, the town planner may require the applicant to hire a Washington State licensed land surveyor to reestablish property corners.

(12) Detached ADUs may be sited on a rear/side lot line only if the lot line abuts an improved public alley pursuant to RCW 36.70A.681(1)(i).

(13) ADUs are permitted on any lot that meets the zone’s minimum lot size required for a dwelling unit.

(14) Eligible properties can have one dwelling unit and two ADUs, for a maximum total of three dwelling units. ADUs can be in any configuration of attached or detached units.

(15) Owner occupancy is not required for either the existing dwelling unit or any ADUs existing and/or proposed.

(16) All attached ADUs are required to have their own separate entrance(s) from the existing dwelling unit. Additionally, attached ADUs are required to be separated internally from the existing dwelling unit by solid wall construction that meets both building and fire codes.

(17) ADUs shall be designed so that the appearance of the building containing the principal residence remains that of a single-family residence. At a minimum, the ADU shall match the exterior materials, design, and pitch of the roof of the principal residence.

(18) ADUs shall comply with the maximum permitted height for the underlying zone. In the residential zone, however, attached ADUs shall not exceed 35 feet above average original grade. Detached ADUs in the residential zone shall not exceed 28 feet average original grade.

(19) Homeowners with existing nonpermitted ADUs must apply for a building permit to make them legal. Units that are not legalized will be subject to enforcement. Preexisting units must meet the same requirements as new ADUs, including but not limited to: zoning, parking, fire, and building code standards/regulations.

(20) RVs, including park model trailers, shall not be used as ADUs.

(21) ADUs are exempt from the density requirements of the underlying zone.

(22) If applicable, impact fees and connection fees associated with the construction of an ADU shall not be greater than 50 percent of the fees that would be imposed on the dwelling unit.

(23) Where practical, the ADUs shall be located and designed to minimize disruption of privacy and outdoor activities on adjacent properties. Strategies to accomplish this include, but are not limited to:

(a) Stagger windows and doors to not align with such features on abutting properties.

(b) Avoid upper-level windows, entries and decks that face common property lines to reduce overlook of a neighboring property.

(c) Install landscaping as necessary to provide for the privacy and screening of abutting property.

(24) Short-Term Rental (STR) Regulations. ADUs shall not be used as short-term rentals (STR) for less than six months (180 days) within a calendar year. [Ord. 887 § 2 (Exh. 1), 2025]

There is no appeal of the town planner’s determination regarding whether to issue a building permit to construct an ADU on a subject property in accordance with CMC 18.08.030(3). [Ord. 887 § 2 (Exh. 1), 2025]

[Ord. 887 § 2 (Exh. 1), 2025]