Snohomish City Zoning Code
CHAPTER 14
170 Accessory Dwelling Units
14.170.010 Purpose.
The purpose of this chapter is to allow accessory dwelling units that are secondary and subordinate to, and either attached to or detached from, a principal building on a residential lot. Accessory dwelling units provide additional housing options that can be more affordable than traditional detached housing. (Ord. 2495, 2024)
14.170.020 Applicability.
An accessory dwelling unit (ADU) is a dwelling unit that is subordinate to a permitted principal unit located on the same lot. “Principal unit” shall be as defined in RCW 36.70A.696. ADUs may be attached to the principal unit or a separate structure. (Ord. 2495, 2024)
14.170.030 General Standards.
A. ADUs shall not be counted toward maximum residential density calculations.
B. Up to two ADUs may be permitted on any lot containing a principal dwelling unit.
C. ADUs shall not be built within critical areas or their buffers, as identified in Chapter 14.255 SMC.
D. The property owner shall be required to reside on the site if any ADU is being used as a short-term rental.
E. New structures containing an ADU that are located in the Historic District, Pilchuck District, or Midtown District shall be subject to design review and findings of consistency with applicable design standards.
F. ADUs shall be subject to payment of impact fees, assessed at 50 percent of the rate that would be applicable to the principal unit in effect at the time of permit issuance. (Ord. 2495, 2024; Ord. 2536, 2026)
14.170.040 Dimensional Requirements.
The following table provides standards required for ADUs. In the event there is a conflict between the provisions of this section with any other provision of the SMC, the provisions of this section shall control.
Subject | Standard |
|---|---|
Number of units | Up to two ADUs per lot containing a principal unit, subject to SMC 14.170.030 |
ADU size | No maximum size; subject to setback requirements |
Maximum building height1 | Located less than 4 feet from an alley: 24 feet |
Setback, front2 | No detached ADU may be placed in the front setback of a lot. Attached ADUs located in the front of the primary dwelling unit shall be subject to the front setback standards of Chapter 14.210 SMC. |
Setback, side2 | Interior lot: 5 feet |
Setback, rear2 | Detached units, located on an alley: No minimum rear setback |
1Building height is measured per SMC 14.210.030.
2The setbacks of this section shall apply unless the standard setbacks of Chapter 14.210 SMC allow a smaller setback for residential structures in the underlying zone.
(Ord. 2495, 2024; Ord. 2536, 2026)
14.170.050 Parking Requirements.
One off-street parking stall shall be required for each ADU on a lot. All other parking standards of Chapter 14.235 SMC shall apply. (Ord. 2495, 2024)
14.170.060 Independent Sale.
ADUs may be individually sold following the condominium process of Chapter 64.90 RCW or through the unit lot subdivision process of SMC 14.215.125. Unit lot subdivision of ADUs shall be an administrative decision. If one or more separate units are created through the condominium or unit lot subdivision process, the ADU(s) shall still be considered accessory to and on the same lot as the principal unit pursuant to SMC 14.170.020. (Ord. 2495, 2024; Ord. 2536, 2026)
