Chapter 22C.180
ACCESSORY STRUCTURES
Sections:
22C.180.020 Accessory structure standards.
22C.180.030 Accessory dwelling unit standards.
22C.180.010 Purpose.
The purpose of this chapter is to allow for residential accessory structures, including secondary dwelling units, to be established which are incidental to the primary residential use of a single-family residence, while ensuring compatibility with surrounding single-family uses. The accessory structure must be clearly secondary to the primary use. Accessory structures or uses may not be established until the principal structure is constructed on the property. (Ord. 2852 § 10 (Exh. A), 2011).
22C.180.020 Accessory structure standards.
In the zones in which a residential accessory structure is listed as a permitted use, the community development director or designee shall review all proposals to construct an accessory structure. The following standards and regulations shall apply to all proposed accessory structures; provided, that accessory dwelling units shall only be allowed in zones where they are a permitted use and shall also comply with the standards set forth in MMC 22C.180.030:
(1) Accessory structures on properties less than one acre in size shall comply with the following density and dimensional requirements:
(a) The footprint of all detached accessory structures shall not exceed the lesser of:
(i) Fifteen percent of the total lot area in the R-4.5, R-6.5, R-8 and WR-R-4-8 zones, or 20 percent of the total lot area in the R-12 through R-28 and WR-R-6-18 zones; or
(ii) Eighty percent of the footprint of the primary residential structure.
(b) The height of all detached accessory structures shall not exceed 20 feet, except that detached accessory structures containing an accessory dwelling unit shall not exceed the base height for the zone.
(c) The community development director may allow minor deviations to these dimensional requirements in order to accommodate industry standards for building dimensions.
(2) A detached garage, carport or other permitted accessory building may be located in the rear yard; provided, that:
(a) Not more than 50 percent of the required rear setback area is covered; and
(b) Accessory structure(s) located within rear setback areas shall have a minimum interior side setback of five feet, or 10 feet on the flanking street of a corner lot, and a minimum rear setback of five feet; and
(c) Vehicle access points from garages, carports, fenced parking areas or other accessory structure(s), the entrance of which faces the rear lot line, shall not be located within 10 feet from the rear lot line, except where the accessory structure’s entrance faces an alley with a right-of-way width of 10 feet, in which case the accessory structure(s) shall not be located within 20 feet from the rear lot line; and
(d) In Planning Area 1 “Downtown Neighborhood,” the rear setbacks outlined in subsections (2)(b) and (c) of this section may be reduced to two feet from the rear lot line; provided, that the alley right-of-way is a minimum of 20 feet in width. Where the alley right-of-way is less than 20 feet in width, the property owner shall be required to dedicate to the city sufficient property to widen the abutting alley to the full width as measured from the design centerline, so as to conform to the applicable road standards specified by the city engineer. Upon dedication of the necessary right-of-way, the rear setback may be reduced to two feet from the rear lot line. Where an existing, nonconforming structure is internally remodeled to include an accessory dwelling unit, but the footprint of the structure is not increased, the structure can be allowed to remain at a zero setback; provided, that the right-of-way is 20 feet in width; and
(e) Detached accessory buildings exceeding one story shall provide the minimum required yard setbacks for principal buildings in the zone; and
(f) An accessory structure, which is located in the rear setback area, may be attached to the principal structure; provided, that no portion of the principal building is located within the required yard setbacks for principal structures in the zone.
(3) A detached garage, carport or other permitted accessory structure may be located in the front or side yard only if the applicant demonstrates to the satisfaction of the community development director that the following conditions can be met:
(a) Accessory structures that are located in the front or side yard, or on the flanking street side of a corner lot, shall be consistent with the architectural character of the residential neighborhood in which they are proposed to be located, and shall be subject to, but not limited to, the following development standards:
(i) The accessory structure shall be consistent with the architectural character of the principal structure; and
(ii) The accessory structure shall have a roof pitch similar to the principal structure and have siding and roofing materials similar to or compatible with those used on the principal structure. No metal siding or roofing shall be permitted unless it matches the siding and roofing of the principal structure, or unless it is a building material that is of a residential character such as metal tab roofing or other products consistent with standard residential building materials. Plans for the proposed accessory structure(s) indicating siding and roofing materials shall be submitted with the application; and
(iii) Detached accessory structures located in the front or side yard shall provide the minimum required front and side yard setback for principal structures in the zone.
(4) The community development director is specifically authorized to allow an increase in the size of a detached accessory structure over the requirements outlined in subsection (1) of this section; provided, that the accessory structure(s) shall be compatible with the principal structure and/or neighborhood character. To make this determination, the community development director may consider such factors that include, but are not limited to, view obstruction, roof pitch, building materials, screening and landscaping, aesthetic impact on surrounding properties and streetscape, incompatible scale with dwellings on surrounding properties, and impact on neighborhood character. The community development director shall also have the authority to impose greater setback requirements, landscape buffers, or other locational or design requirements as necessary to mitigate the impacts of accessory structures which are greater in size than otherwise allowed by this section. (Ord. 3093 § 4, 2018; Ord. 2898 § 14, 2012; Ord. 2852 § 10 (Exh. A), 2011).
22C.180.030 Accessory dwelling unit standards.
In the zones in which an accessory dwelling is listed as a permitted use, the community development director shall review all proposals to establish an accessory dwelling unit. The following standards and regulations shall apply to all proposed accessory dwelling units:
(1) An owner-occupant of a single-family dwelling unit may establish only one accessory dwelling unit per residential lot, which may be attached to the single-family dwelling or detached in an accessory building. An accessory dwelling unit may not be located on a lot on which a temporary dwelling, as defined in Chapter 22C.110 MMC, is located.
(2) The single-family dwelling unit must be owner-occupied on the date of application and remain owner-occupied for as long as the accessory unit exists. A covenant shall be required to be recorded with the Snohomish County auditor ensuring owner occupancy, prior to granting occupancy of the accessory dwelling unit.
(3) The floor area of the accessory dwelling unit shall not exceed 50 percent of the total floor area of the single-family dwelling, and shall comply with the density and dimensional requirements set forth in MMC 22C.010.080.
The community development director is authorized to conditionally allow an attached accessory dwelling unit greater than the maximum size limit within existing structures, when a denial of such an increase would result in an unreasonable division of interior space between the ADU and the primary dwelling unit.
(4) The community development director is authorized to conditionally allow a deviation of the setbacks set forth in MMC 22C.010.080 of an existing detached accessory structure to be converted to an accessory dwelling unit, subject to the following conditions:
(a) The application shall be subject to the public notice criteria outlined in MMC 22G.010.090 and is subject to a $250.00 permit processing fee in addition to the accessory dwelling unit land use review fee outlined in MMC 22G.030.020;
(b) The existing detached accessory structure was constructed prior to the effective date of Ordinance 3093, adopted on May 14, 2018;
(c) The applicant shall be required to demonstrate that the existing detached accessory structure was legally permitted and complied with the required structure setbacks in effect at the time the accessory structure was constructed;
(d) If the existing detached accessory structure is determined to be legal nonconforming, conversion to an accessory dwelling unit shall not increase the pre-existing degree of nonconformance;
(e) The accessory dwelling unit shall not result in a lack of compatibility with existing and potential uses in the immediate area;
(f) Adverse impacts of the proposed accessory dwelling unit shall be mitigated by site design elements such as landscaping, fencing and general visual improvement of the property; and
(g) Adequate provisions must be made for public improvements such as sewer, water, drainage, pedestrian and vehicular circulation.
(5) In no case shall the accessory dwelling unit be less than 200 square feet in size, or have more than two bedrooms. Floor areas shall be exclusive of garages, porches, or unfinished basements.
(6) In no case shall a detached accessory dwelling unit have axles or be on a chassis.
(7) The architectural character of the single-family dwelling shall be preserved. Exterior materials, roof form, and window spacing and proportions shall match that of the existing single-family dwelling. Only one main entrance shall be permitted on the front (street face) of the dwelling; provided, that this limitation shall not affect the eligibility of a residential structure that has more than one entrance on the front or street side on the effective date of the ordinance codified in this chapter.
(8) One off-street parking space shall be provided and designated for the accessory dwelling unit, unless the accessory dwelling unit is located within one-quarter mile of a major transit stop. No additional parking is required for accessory dwelling units within one-quarter mile of a major transit stop.
If parking is required, driveways may be counted as one parking space but no parking areas other than driveways shall be created in front yards. When the property abuts an alley, the off-street parking space for the accessory dwelling unit shall gain access from the alley.
(9) The owner-occupant(s) may reside in the single-family dwelling unit or the accessory dwelling unit.
(10) Accessory dwelling units are not permitted as a short-term rental.
(11) In addition to the conditions that may be imposed by the community development director, all accessory dwelling units shall also be subject to the condition that such a permit will automatically expire whenever:
(a) The accessory dwelling unit is substantially altered and is thus no longer in conformance with the plans approved by both the community development director and the building official; or
(b) The subject lot ceases to maintain at least three off-street parking spaces, when said accessory dwelling unit is beyond one-quarter mile from a major transit stop; or
(c) The owner ceases to reside in either the principal or the accessory dwelling unit; provided, that in the event of illness, death or other unforeseeable event which prevents the owner’s continued occupancy of the premises, the community development director may, upon a finding that discontinuance of the accessory dwelling unit would cause a hardship on the owner and/or tenants, grant a temporary suspension of this owner-occupancy requirement for a period of one year. The community development director may grant an extension of such suspension for one additional year, upon a finding of continued hardship. (Ord. 3203 § 8, 2022; Ord. 3093 § 5, 2018; Ord. 2852 § 10 (Exh. A), 2011).