Title 17C Land Use Standards
Chapter 17C.110 Residential Zones
The standards of this section allow for development on lots, but do not legitimize lots that were divided in violation of chapter 17G.080 SMC, Subdivisions. The required minimum lot size, lot depth, lot width and frontage requirements for new lots ensure that development will, in most cases, be able to comply with all site development standards. The standards also prevent the creation of very small lots that are difficult to develop at their full density potential. Finally, the standards also allow development on lots that were reduced by condemnation or required dedications for right-of-way.
Existing Lot Size.
Development is prohibited on lots that are not of sufficient area, dimension and frontage to meet minimum zoning requirements in the base zone. Except:
one single-family residence may be developed on a lot that was legally created under the provisions of chapter 58.17 RCW, Plats – Subdivisions – Dedications, or applicable platting statutes;
a PUD lot may be less than the minimum size of the base zone, if such lot is delineated on a PUD plan, which has been approved by the hearing examiner. All use and development standards of the zone wherein such lot is located, shall be complied with, unless modified through the PUD process by the hearing examiner. A PUD shall comply with the requirements of subsection (C) of this section.
No lot in any zone may be reduced so that the dimension, minimum lot area, frontage or area per dwelling unit is less than that required by this chapter, except as modified through the PUD process by the hearing examiner.
Lots Reduced by Condemnation or Required Dedication for Right-of-way. Development that meets the standards of this chapter is permitted on lots, or combinations of lots, that were legally created and met the minimum size requirements at the time of subdivision, but were reduced below one or more of those requirements solely because of condemnation or required dedication by a public agency for right-of-way.
All new lots created through subdivision must comply with the standards for the base zone listed in Table 17C.110-3.
For sites two acres or greater, transition lot sizes are required to be included as a buffer between existing platted land and new subdivision subject to the requirements of this section. The purpose of this section is to transition lot sizes between the proposed and existing residential developments in order to facilitate compatible development and a consistent development pattern. In the RA and RSF zones, the minimum lot size is subject to transitioning of lots sizes. Lots proposed within the initial eighty feet of the subject property are required to transition lot sizes based on averaging under the following formulas:
Transitioning is only required of properties adjacent to or across the right-of-way from existing residential development. “Existing residential development” in this section shall mean existing lots created through subdivision or short plat.
Lot size in the transition area is based on the average of the existing lot size in subdivisions adjacent to, or across the street from, the subject property. Lots greater than eleven thousand square feet are not counted in the averaging.
If the existing average lot size is greater than seven thousand two hundred square feet, then the lot size in the transition area can be no less than seven thousand two hundred square feet.
If the existing average lot size is less than seven thousand two hundred square feet, then the lot size in the transition area can be equal to or greater than the average.
If the subject site shares boundaries with more than one subdivision, the minimum lot size in the transition area shall be based on the average lot sizes along each boundary. When two boundaries meet, the lot size shall be based on the larger of the two boundaries. See example below; and
If the subject site shares a boundary with property zoned other than RA or RSF, then there are no transition requirements along that boundary.
After the first set of lots in the transition area, lot sizes may be developed to the minimum lot size of the base zone, i.e., four thousand three hundred fifty square feet in the RSF zone.
Planned unit developments, combined with a subdivision, may reduce the minimum lot size, lot with, lot depth and frontage requirements in the RA and RSF zones pursuant to SMC 17G.070.030(C)(1), except in the transition area required by subsection (C)(1) of this section.
Ownership of Multiple Lots.
Where more than one adjoining lot is in the same ownership, the ownership may be separated as follows:
If all requirements of this chapter will be met after the separation, including lot size, density and parking, the ownership may be separated through either a boundary line adjustment (BLA) or plat, as specified under chapter 17G.080 SMC, Subdivisions.
If one or more of the lots does not meet the lot size standards in this section, the ownership may be separated along the original plat lot lines through a boundary line adjustment (BLA).
New Development on Standard Lots. New development on lots that comply with the lot size standards in this section are allowed subject to the development standards and density requirements of the base zone as required under Table 17C.110-3.
Lot Frontage. All residential lots shall front onto a public street and meet the minimum lot frontage requirements of Table 17C.110-3. Except, that frontage on a public street is not required for lots created through alternative residential subdivision under SMC 17G.080.065, and lots approved in a planned unit development or a manufactured home park may have lots or spaces fronting onto private streets, subject to the decision criteria of SMC 17H.010.090.
DEVELOPMENT STANDARDS 
RSF & RSF-C
Density - Maximum
4,350 (10 units/acre)
2,100 (20 units/acre)
1,450 (30 units/acre)
Density - Minimum
11,000 (4 units/acre)
2,900 (15 units/acre)
MINIMUM LOT DIMENSIONS
LOTS TO BE DEVELOPED WITH:
Multi-Dwelling Structures or Development
Minimum Lot Area
2,900 sq. ft.
Minimum Lot Width
Minimum Lot Depth
Minimum Front Lot Line
Compact Lot Standards 
Minimum Lot Area 
3,000 sq. ft.
Attached Houses as defined in SMC 17A.020.010
7,200 sq. ft.
4,350 sq. ft.
1,600 sq. ft.
1,450 sq. ft.
36 ft. or 16 ft. with alley parking and no street curb cut
Same as lot width
Same as lot Width
1,800 sq. ft.
4,200 sq. ft.
Maximum Building Coverage
Lots 5,000 sq. ft. or larger
2,250 sq. ft. +35% for portion of lot over 5,000 sq. ft.
Lots 3,000 - 4,999 sq. ft.
1,500 sq. ft. + 37.5% for portion of lot over 3,000 sq. ft.
Lots less than 3,000 sq. ft.
Attached housing as defined in SMC 17A.020.010, lots any size
Same as above
Up to 70%
Up to 80%
Maximum Roof Height
35 ft. 
35 ft. 
Maximum Wall Height
Floor Area Ratio (FAR)
Front Setback [7, 8]
Side Lot Line Setback – Lot width more than 40 ft.
Side Lot Line Setback – Lot width 40 ft. or less
Street Side Lot Line Setback 
Rear Setback [9, 10]
25 ft. 
Required Outdoor Area
Required Outdoor Area for attached and detached houses. Minimum dimension (See SMC 17C.110.223)
250 sq. ft.
12 ft. x 12 ft.
200 sq. ft.
10 ft. x 10 ft.
48 sq. ft.
7 ft. x 7 ft.
Maximum Coverage 
See Primary Structure
Side Lot Line Setback – Lot width 40 ft. or wider 
Side Lot Line Setback – Lot width less than 40 ft. 
Street Side Lot Line 
Rear with Alley
-- No requirement
 Plan district, overlay zone, or development standards contained in SMC 17C.110.310 through 360 may supersede these standards.
 See SMC 17C.110.209, Compact Lot Standards.
 For developments two acres or greater, lots created through subdivision in the RA, RSF and the RSF-C zones are subject to the lot size transition requirements of SMC 17C.110.200(C)(1).
 In the RSF-C and RTF zones, and sites in the RSF zone qualifying for compact lot development standards, described in SMC 17C.110.209, FAR may be increased to 0.65 for attached housing development only.
 No structure located in the rear yard may exceed twenty feet in height.
 Base zone height may be modified according to SMC 17C.110.215, Height.
 Attached garage or carport entrance on a street is required to be setback twenty feet from the property line.
 See SMC 17C.110.220(D)(1), setbacks regarding the use of front yard averaging.
 See SMC 17C.110.220(D)(2), setbacks regarding reduction in the rear yard setback.
 Attached garages may be built to five feet from the rear property line except, as specified in SMC 17C.110.225(C)(6)(b), but cannot contain any living space.
 In the RSF-C zone and sites in the RSF zone qualifying for compact lot development standards, described in SMC 17C.110.209, the rear setback is 15 feet.
 Maximum site coverage for accessory structures is counted as part of the maximum site coverage of the base zone.
 Setback for a detached accessory structure and a covered accessory structure may be reduced to zero feet with a signed waiver from the neighboring property owner, except, as specified in SMC 17C.110.225(C)(5)(b).
 The setback for a covered accessory structure may be reduced to five feet from the property line.
Date Passed: Monday, January 14, 2019
Effective Date: Wednesday, February 27, 2019
ORD C35730 Section 1