Mukilteo City Zoning Code
CHAPTER 17
20 BULK REGULATIONS
§ 17.20.010 Purpose.
The purpose of this chapter is to establish standards for the size, scale, and placement of structures. These regulations are intended to balance the rights of property owners with the public interest in promoting orderly development, protecting neighborhood character, preserving views, preventing overcrowding, and ensuring adequate light, air, and privacy.
(Ord. 1516 § 8 (Exh. E), 2025)
§ 17.20.020 Applicability.
A.
New and Altered Lots. The dimension and density standards in this chapter apply to all newly created lots and to lot line adjustments.
B.
New and Expanded Structures. This chapter applies to all new structures and to additions to existing structures.
C.
Exceptions.
1.
The city council may authorize a development agreement pursuant to the procedures of RCW 36.70B.170 through 36.70B.210 that modifies development standards on a site-specific basis.
2.
Where a lot line adjustment of a nonconforming lot cannot achieve full conformity with these regulations but would reduce the nonconformity, it may be approved.
D.
Conflicts. When the standards in this chapter conflict with other applicable laws or regulations, the more restrictive standard applies.
(Ord. 1516 § 8 (Exh. E), 2025)
§ 17.20.030 Lot standards.
A.
Lot Bulk Matrix.
Zone | Minimum Lot Area | Maximum Density | Minimum Lot Width | Minimum Lot Depth |
|---|---|---|---|---|
RD 12.5/12.5(S) | 12,500 sf | Each lot may have 1 duplex or 1 single-family dwelling with up to 2 ADUs | 50' for internal lots 60' for corner lots | 85' |
RD 9.6/9.6(S) | 9,600 sf | |||
RD 8.4 | 8,400 sf | |||
RD 7.5 | 7,500 sf | |||
RD 7.2 | 7,200 sf | |||
MRD | 7,500 sf | 1 dwelling unit/3,300 sf (fractions > 0.75 rounded up) | ||
MR | 7,500 sf | 1 dwelling unit/2,000 sf (fractions > 0.75 rounded up) | ||
All other zones | None | None | None | None |
B.
Density Bonus for Affordable Housing on Properties Owned by Religious Organizations. Properties owned by a religious organization, and located in a zone that allows residential uses, may have residential densities that are one hundred fifty percent of what is allowed in the underlying zone if:
1.
Built exclusively for low-income households;
2.
Protected as affordable housing for a period of at least fifty years;
3.
In compliance with federal fair housing laws;
4.
Units are managed in compliance with federal fair housing; and
5.
Project is designed to be responsive to the transit needs of the residents.
C.
Public Takings Exceptions to Lot Requirements. When part of a legally existing lot is taken for public use, the remaining portion is still considered buildable if it:
1.
Has access to a dedicated street or easement;
2.
Has a buildable area of at least thirty-five by forty-five feet, excluding setbacks;
3.
Can accommodate a ten-foot front and rear setback and achieve fifty percent of the side yard setback of the underlying zone; and
4.
Complies with health department requirements.
(Ord. 1516 § 8 (Exh. E), 2025)
§ 17.20.040 Structure standards.
A.
Structure Bulk Matrix. General standards outlined in table below, with letters to note where additional standards or exceptions may apply.
Zone | Maximum Lot Coverage | Maximum Building HeightC | Front SetbackB, D (and side adjacent to a street) | Side SetbackB, D (not adjacent to street) | Rear SetbackB, D |
|---|---|---|---|---|---|
RD 12.5 | 30% | 30' | 25' E, F | 5' E, F | 25' E, F |
RD 12.5(S) | 35% | 35' | 20' E, F | 5' E, F | 5' E, F |
RD 9.6 | 35% | 30' | 25' E, F | 5' E, F | 20' E, F |
RD 9.6(S) | 35% | 35' | 20' E, F | 5' E, F | 5' E, F |
RD 8.4 | 35% | 35' | 20' E, F | 5' E, F | 5' E, F |
RD 7.5 | 35% | 30' | 20' E, F | 5' E, F | 20', or 15' for corner lots E, F |
RD 7.2 | 35% | 35' | 20' E, F | 5' E, F | 5' E, F |
MRD | 40% | 35' | 25' | 5' | 20', or 5' for single-family dwellings |
MR | 40% | 35' | 25' | 5' | 25' Reduced to 5' for single-family dwellings |
WMU | none | 25' north of Front Street 45' south of Front Street | none | none | none |
DB | none | 35' | none | none | none |
CB | none | 35' | 10' | None, except 10' for commercial uses abutting residential zone | None, except 15' for commercial uses abutting residential zone |
CB(S) | 50% | 35' | 25' | None, except 10' next to residential zones | None, except 10' next to residential zones |
PCB | none | 35' | None, except 10' for commercial uses abutting residential zone | None, except 10' next to residential zone | 20' |
PCB(S) | none | 40', except 65' adjacent to 106th Street and north | 25' | None, except 10' next to residential zones | None, except 25' next to residential zones |
BP | 35% | 50' | 30' | None, except 25' next to residential zones | None, except 25' next to residential zones |
PI | 40% | 35' | 10', except 20' next to residential zone | 10' | 20' |
IP | 50% | 65' | 30' plus one foot for each foot of building height > 45' | None, except 25' next to residential zones | None, except 25' next to residential zones |
LI | none | 65', except 50' when within 350' of SR-525, Beverly Park Road, or 132nd St SW | 25' | None, except 50' next to residential zones | None, except 50' next to residential zones |
HI | none | 65' | 25' | None, except 50' next to residential zones | None, except 50' next to residential zones |
PSP | 55% | 35' | 10' | None, except 25' next to residential zones | None, except 25' next to residential zones |
OS | none | 35' | none | None, except 20' next to residential zones | None, except 20' next to residential zones |
B.
Additional Private Access Setbacks.
Building Type | Setbacks |
|---|---|
Single Family | 10 feet from common driveways 20 feet from private roads providing access to parcel 10 feet from private roads not providing access to parcel |
Multifamily and Mixed-Use | 10 feet from internal drive aisles for ground floor |
Other Types | Not applicable |
C.
Exceptions to Maximum Height Standards.
1.
Sports Courts. Fences surrounding publicly accessible sports courts, athletic fields, and other outdoor recreation uses may exceed the fence height restrictions of the zone in which they are located.
2.
The following exceptions apply to commercial, industrial, multifamily, and mixed-use buildings:
a.
Appurtenances such as stairwells, chimneys, rooftop guardrails that are at least fifty percent transparent, mechanical equipment, and elevator shafts may exceed the maximum building height by up to ten feet.
b.
Residential or commercial radio towers, television and radar transmission and/or reception towers, flag poles, water towers, bell towers, church spires, and monuments may exceed the height limits of the underlying zone as long as they are less than one hundred feet tall.
D.
Permitted Encroachments Into Setbacks.
1.
Fences and walls (including retaining walls) up to six feet tall are allowed in required setbacks if they comply with sight distance triangle provisions.
2.
Eaves, cornices, chimneys, flues, projecting windows and similar ornamental features or mechanical equipment may project up to two feet into setbacks.
3.
Uncovered porches, decks, or steps less than four feet tall at the point of connection to the building may project up to eight feet into front and rear setbacks and up to two feet into side setbacks.
E.
Setback Reductions in RD zones. The following reductions in the bulk matrix standards apply to single-family residential structures:
1.
Front Yard Reductions to Match Historic Development Patterns. If over sixty percent of lots on a block have an average front setback less than the required minimum, new construction may match this block average. Vacant lots are assumed to meet current setbacks.
2.
Front Yard Reductions for Sloped Lots. For lots with street frontage and slopes over thirty percent, the front setbacks may be reduced by one foot per one percent of slope above thirty percent up to a fifteen-foot reduction.
3.
Rear Yard Reductions for Legal Nonconforming Lots. On legal nonconforming lots with a depth of less than eighty-five feet, the rear setback may be reduced to fifteen feet.
F.
Setback Requirements for Accessory Structures. In RD zones, the following setbacks apply to accessory structures not used as dwelling units:
1.
Temporary structures made of plastic, canvas, tarps, or other similar materials are prohibited.
2.
All accessory structures must have a pitched roof.
3.
Detached garages over one story must be set back twenty feet further from the front property line than the principal dwelling.
4.
Setbacks may be reduced to:
a.
Eight-foot rear setback when the structure is sixteen feet or less in height and the rear lot line abuts an alley.
b.
Five-foot rear setback when the structure is sixteen feet or less in height and the rear lot line abuts a single-family residential lot.
c.
Zero for rear and side yard setbacks for detached buildings twelve feet or less in height and one hundred twenty square feet or smaller, provided no more than one accessory structure is within five feet of the rear and/or side lot line.
(Ord. 1516 § 8 (Exh. E), 2025)
§ 17.20.050 Maximum hard surface coverage.
A.
Legal Nonconforming Hard Surfaces. Sites with hard surface areas developed before December 31, 2016, that exceed current limits, may maintain their established coverage. Any new hard surface areas must be offset by removing an equal amount of existing hard surface so that the net amount of hard surface is unchanged.
B.
Required Dedications. When public land dedications are required as a condition of approval, the hard surface coverage is calculated based on the square footage of the lot prior to dedication.
C.
Hard Surface Matrix. Achievable hard surface area will be limited by the tree retention standards in Chapter 17.59, but in no case may the hard surface on a property exceed the limits established in the table below.
Use Type | Maximum Hard Surface Coverage |
|---|---|
Single-family residential and duplexes | 3,000 square feet for lots < 6,000 square feet 50% for all other lots |
Townhouses and multifamily | 80% |
Commercial and mixed-use | 90% |
Industrial | 95% |
Downtown business (DB) zone | 100% |
(Ord. 1516 § 8 (Exh. E), 2025)
§ 17.20.060 Fences and freestanding walls.
B.
Height.
1.
Measuring. Fence and wall height are measured from the lowest point touching the ground to the highest point. If a fence is on top of a rockery or retaining wall, the fence must be set back at least two feet in order to be measured separately. Otherwise, the height includes the wall and fence.
2.
Residential Zones. Fences and freestanding walls in residential zones may not exceed six feet within side and rear yard setback areas and four feet in front yard setbacks.
3.
Commercial and Industrial Zones. Fences and freestanding walls in commercial and industrial zones may not exceed eight feet in height.
4.
Schools and Utility Substations. Schools and utility substations may have fences up to eight feet in height as long as they comply with sight distance triangle requirements.
5.
Sight Distance Triangle. All fences and walls must comply with sight distance triangle requirements.
C.
Administrative Modifications. If strict application of this section limits reasonable screening of a property, the director may allow a height increase of up to two feet above the standards. Height increases of more than two feet require a variance.
(Ord. 1516 § 8 (Exh. E), 2025)
§ 17.20.070 Sight distance triangle.
A.
Prohibitions on Sight-Obscuring Structures and Vegetation. No fences, walls, hedges, or similar features taller than forty-two inches may be located within the sight distance triangle.
B.
Measuring.
1.
At uncontrolled intersections, the sight distance triangle is formed by connecting the centerlines of intersecting streets to points one hundred feet away along the centerline.
2.
At controlled intersections, the sight distance triangle is formed by connecting the centerlines of the intersecting streets to a point ten feet back from the stop bar on one street and a point the sight distance away along the other street's centerline.
3.
Limited Turn Movements. Where left turns are restricted, only the relevant direction requires a sight distance triangle.
C.
Standards.
1.
Uncontrolled Intersections. The sight distance is one hundred feet.
2.
Uncontrolled Intersections. The sight distance is based on the table below.
Posted Speed Limit (on the public r-o-w) | 25 mph | 30 mph | 35 mph | 40 mph |
Sight Distance | 300' | 400' | 530' | 600' |
 Diagram A Sight Distance at Uncontrolled Intersections |
 Diagram B Sight Distance at Uncontrolled Intersections |
(Ord. 1516 § 8 (Exh. E), 2025)