Marysville, WA Accessory Structures: ADU Rules (2026)
ADU rules in Marysville, WA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- ADUs allowed per lot
- Two (single-family or qualifying middle housing)
- Owner-occupancy requirement
- None
- ADU size range
- 200 to 1,400 sq ft
- Max height
- 30 feet
- Side / rear setback
- 5 ft side; 15 ft rear
- Structure separation
- 5 feet minimum
- Review authority
- Community development director
Summary
Marysville allows two accessory dwelling units per single-family lot with no owner-occupancy requirement, a change driven by Washington's 2023 ADU law. Under MMC Section 22C.185.020, each unit must run 200 to 1,400 square feet, stay under 30 feet tall, and meet five-foot side and 15-foot rear setbacks, with review by the community development director.
Table 1. Number of accessory dwelling units allowed per lot: Two. Allowed accessory dwelling unit configurations: (a) One attached unit and one detached unit; (b) Two attached units; or (c) Two detached units, which may be comprised of either one or two detached structures. Minimum size per accessory dwelling unit: 200 SF gross floor area. Maximum size per accessory dwelling unit: 1,000 SF gross floor area or 50 percent of the total floor area of the single-family residence, whichever is greater; provided, that in no case shall an accessory dwelling unit exceed 1,400 square feet. Maximum bedrooms per accessory dwelling unit: Two. Side setback: Five feet. Side street setback: 10 feet along nonarterials; 15 feet along arterials. Rear yard setback: 15 feet; provided, that the rear yard setback may be reduced to 10 feet for one-story structures, or for structures located in a PRD. Height: 30 feet.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4922912; v1 updated 2026-06-08; through 06-08-2026).
Full Breakdown
020 lets a lot developed with a single-family residence carry two accessory dwelling units, arranged as one attached and one detached unit, two attached units, or two detached units in one or two structures. 080, and those ADUs count toward that total density. The chapter's Table 1 sets no owner-occupancy requirement for either the principal dwelling or the ADU, reflecting the state's 2023 ADU law, which bars cities from conditioning ADU permits on the owner living on site. Each ADU must be at least 200 square feet of gross floor area and no more than 1,000 square feet or half the floor area of the single-family residence, whichever is larger, capped in every case at 1,400 square feet, with a maximum of two bedrooms and a height limit of 30 feet.
Setbacks run five feet on the side, 10 feet along nonarterial side streets and 15 feet along arterials, and 15 feet at the rear, reducible to 10 feet for a one-story ADU or one in a planned residential development. Structures must sit at least five feet apart, and a five-foot paved, obstruction-free path must connect the ADU's front entrance to the addressed property line for emergency access. The director can approve a larger unit for an existing structure conversion or to avoid an unreasonable division of interior space, and existing structures like detached garages may convert to an ADU even if their setbacks or coverage predate current standards.
The architectural character, materials, roofline and window proportions of the primary house must be preserved, and a detached ADU can never be built on a chassis with axles.
Violations & Fines
Building or maintaining an ADU that doesn't meet Section 22C.185.020's Table 1 standards is a Title 22C land use violation under MMC Section 4.02.040(3)(g): $150 for a first noncommercial offense ($250 commercial), $300/$500 for a second violation, and misdemeanor charges for a third within two years. The community development director can also order the ADU's use discontinued if it no longer matches its approved plans or the lot loses its required parking, though use may resume once the deficiency is fixed.
Frequently Asked Questions
How many ADUs can I build on my Marysville lot?
Do I have to live on the property to build an ADU in Marysville?
How large can a Marysville ADU be?
Can I convert my detached garage into an ADU?
Sources & Official References
Other rules in Marysville
How Marysville compares: Easiest Cities to Build an ADU·Compare Marysville to another location·View the Washington accessory structures overview
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ADU Rules in Nearby Cities
How other cities in Snohomish County handle adu rules.