HomeMy WebLinkAboutRMC 4-2-110C_DEVELOPMENT STANDARDS FOR ACCESSORY DWELLING UNITS_COMPLETE4-2-110C DEVELOPMENT STANDARDS FOR RESIDENTIAL DEVELOPMENT (ACCESSORY
DWELLING UNITS) 4-2-110C1 DEVELOPMENT STANDARDS FOR ACCESSORY DWELLING
UNITS
1. PURPOSE AND INTENT: The provisions of this subsection are available as an opportunity to
augment local housing inventory, diversify housing type and size, and create opportunities for
homeownership. Accessory Dwelling Units (ADUs) are well-suited for smaller households, older
adults aging in place, people with disabilities, individuals on fixed incomes, and others seeking
affordable living arrangements.
2. APPLICABILITY: The provisions of this subsection shall apply to the development of ADUs when
located on the same lot as a principal dwelling within the following residential zones: Resource
Conservation (RC), Residential-1 (R-1), Residential-4 (R-4), Residential-6 (R-6), Residential-8 (R-8),
Residential-10 (R-10), and Residential-14 (R-14). ADUs proposed as an accessory use to a religious
institution or social service organization shall follow the provisions of RMC 4-2-080A.7, Conditions
Associated with Zoning Use Tables and RMC 4-9-030D and 4-9-030I, Conditional Use Permits.
3. ADDITIONAL REQUIREMENTS: All applicable health and safety standards shall apply. Nothing
in this subsection requires the issuance of a building permit for ADUs if other federal, state, and
local requirements for a building permit are not met, including but not limited to building, fire, and
energy code requirements, adequate access to utility services, emergency services, etc.
4. DEVELOPMENT STANDARDS: The following development standards are established for ADUs:
GENERAL REQUIREMENTS4, 10
Maximum Number of
Units24
Two (2) ADUs are allowed per legal lot as an accessory use to a principal
dwelling.
Configuration Either one (1) attached ADU and one (1) detached ADU, two (2) attached ADUs, or two (2) detached ADUs. ADUs may be established within or as
an addition to the principal dwelling.
In RC, R-1, R-4, R-6, and R-8 zones, when two (2) ADUs are proposed, the
second ADU shall comply with the location and setback requirements applicable to the principal dwelling.
Maximum Gross Floor
Area40
1,000 sq. ft.
Maximum Building Area26, 41 1,000 sq. ft.
Conversions25 If a conversion unit occupies an entire single floor of the primary dwelling, it may be allowed to increase the maximum unit size to
efficiently use all the floor area. Conversion units greater than 1,250 sq.
ft. shall be classified as an attached dwelling rather than ADU.
Parking20 A minimum of 1.0 parking space per dwelling unit.
No off-street parking required for ADUs located on lots within a ½ mile
walking distance from a Major Transit Stop.
Formatted: Normal
Field Code Changed
Field Code Changed
Field Code Changed
Formatted: Font: Not Bold, Superscript
Design Standards See RMC 4-2-115, Residential Design Standards.
ATTACHED AND INTERNAL ADUs
Setbacks and
Building Height
ADUs shall comply with the standards applicable to primary structures,
pursuant to RMC 4-2-110A, Development Standards for Residential Low
Density and Medium Density Zones – Primary Structures, and RMC 4-2-110B, Development Standards for Residential High Density Zones.
DETACHED ADUs
Front Yard and Secondary
Front Yard Setbacks
ADUs shall comply with the location and front yard setback requirements
of the underlying zone, pursuant to RMC 4-2-110A, Development
Standards for Residential Low Density and Medium Density Zones and RMC 4-2-110B, Development Standards for Residential High Density Zones.
Detached ADUs shall be located at least 4 ft. from any residential
structure otherwise the structure shall be considered an attached ADU.
Side Yard Setbacks RC and R-1 zones: 25 ft.
R-4, R-6, and R-8 zones: 5 ft.
R-10 and R-14 zones: 4 ft.
Rear Yard Setbacks 5 ft. When located within 10 ft. of the rear property line, at least 25% of
the lineal length of the rear yard shall remain unoccupied from accessory
dwellings.
ADUs may be sited at the rear lot line where an alley is present.
Building Height23, 42 24 ft. measured to the highest point of a flat roof or the highest ridge of a
pitched roof.
MAXIMUM NUMBER AND SIZE
General17
RC, R-1, R-4, R-6, R-8, R-10, and R-14
1 ADU is permitted per legal lot. Unit size shall be determined by lot size and the size of
the primary structure; the total gross floor area of the ADU
shall not exceed the size stated in the Maximum Unit Size
section of this table or 75% of the total gross floor area of
the primary structure, whichever is smaller.41
MAXIMUM UNIT SIZE
Lot Area: Maximum ADU Size40, 41
3,000 sq. ft. or less 600 sq. ft.
3,001 – 4,999 sq. ft. or
less 700 sq. ft.
5,000 – 6,999 sq. ft. or
less 800 sq. ft.
7,000 – 8,999 sq. ft. or
less 900 sq. ft.
Greater than 9,000 sq.
ft. 1,000 sq. ft.
MAXIMUM WALL PLATE HEIGHT10, 18, 19, 41
RC, R-1, R-4, R-6, R-
8, R-10 and R-14
ADUs are subject to the maximum wall plate height of
RMC 4-2-110A, and associated conditions and shall not be taller than the primary structure. Additional ADU height
allowances may be permitted upon application and
approval of a modification pursuant to RMC 4-9-250.42
LOCATION
General
RC, R-1, R-4, R-6, R-
8, R-10 and R-14
ADUs shall be located at least 4 ft. from any residential
structure.
MINIMUM SETBACKS4, 41
Front Yard and Secondary Front Yard
RC, R-1, R-4, R-6, R-
8, R-10 and R-14
The ADU shall be set back an additional 5 ft. parallel to
and measured from the front facade of the primary
structure and shall comply with the setbacks applied to the primary structure, as identified in RMC 4-2-110A,
Development Standards for Residential Zoning
Designations. ADUs shall not be permitted between the primary
structure and the street unless approved in the Conditional Use Permit process.
Side Yard
RC and R-1 25 ft.
R4, R-6 and R-8 5 ft.
R-10 and R-14 4 ft.
Rear Yard
RC, R-1, R-4, R-6, R-8, R-10 and R-14
5 ft. When located within 10 ft. of the rear property line, at least
25% of the lineal length of the rear yard shall remain unoccupied from accessory dwellings, except when the
rear property line abuts an alley.
Clear Vision Area
RC, R-1, R-4, R-6, R-
8, R-10 and R-14
In no case shall a structure over 42 in. in height intrude
into the 20 ft. clear vision area defined in RMC 4-11-030.
CRITICAL AREAS
General
RC, R-1, R-4, R-6, R-
8, R-10 and R-14
See RMC 4-3-050, Critical Areas Regulations, and 4-3-
090, Shoreline Master Program Regulations.
1 Please see Section 4-2-110I, Conditions Associated with Residential Development Standards Tables, for
explanation of table footnotes.