Mukilteo City Zoning Code
CHAPTER 17
30 ACCESSORY DWELLING UNITS
§ 17.30.010 Purpose.
The purpose of this chapter is to expand the supply and variety of housing in the city in a manner that protects the integrity of existing neighborhoods while increasing affordable housing options.
(Ord. 1516 § 11 (Exh. G), 2025)
§ 17.30.020 Applicability.
This chapter applies to the creation of any accessory dwelling unit. This chapter applies to units up to one thousand square feet that are added to an existing residence, located in a new structure, or created through an interior remodel. Dwelling units over one thousand square feet are not considered accessory dwelling units.
(Ord. 1516 § 11 (Exh. G), 2025)
§ 17.30.030 Development standards.
A.
Maximum Number of Units. A maximum of two accessory dwelling units are allowed on a single-family residential lot. Accessory dwelling units are not allowed in cottage housing developments.
B.
Maximum Unit Size. No accessory dwelling unit may have a habitable floor area larger than one thousand square feet.
C.
Maximum Height. Accessory dwelling units may be a maximum of twenty-four feet tall unless located over a garage, in which case the maximum height shall be the height of the underlying zone.
D.
Minimum Setbacks. Accessory dwelling units in new or expanded structures shall conform to the setbacks for the underlying zoning district, except:
1.
Conversions of an existing nonconforming structure into an ADU is permitted when there is no expansion of the structure; and
2.
Setback may be reduced to zero for lot lines abutting an alley; and
3.
To encourage the development of housing units suitable for people with disabilities, the director may allow encroachments into setbacks without a variance to accommodate features that facilitate accessibility, such as ramps.
E.
Access. Each residential lot is limited to one driveway unless the director approves an exception based on unusual circumstances. No new frontage improvements are required for the installation of an ADU.
G.
Addressing. The address for the accessory dwelling unit must be different from the address for any other dwelling units on the same lot.
(Ord. 1516 § 11 (Exh. G), 2025)