Marysville, WA Accessory Structures: Tiny Homes (2026)
Tiny home rules in Marysville, WA, covering tiny houses on wheels (THOWs), park model RVs, and tiny home on foundation builds, determine where they are legal and how they get permitted.
Key Facts
- Wheeled/chassis units
- Not allowed as ADUs
- Max ADU size
- 1,400 sq ft
- ADUs per lot
- Two (state-mandated floor)
- Rear setback
- 15 ft (10 ft one-story)
Summary
Marysville allows up to two accessory dwelling units per lot under state-mandated ADU rules, but a detached ADU can't have axles or sit on a chassis: ruling out tiny homes on wheels as legal ADUs.
The architectural character of the single-family dwelling shall be preserved. Exterior materials, roof form, and window spacing and proportions shall match that of the existing single-family dwelling. In no case shall a detached accessory dwelling unit have axles or be on a chassis.
(3) The city may not prohibit the sale or other conveyance of a condominium unit independently of the principal structure solely on the grounds that the condominium unit was originally built as an accessory dwelling unit.
(4) The provisions of this section do not apply to portions of lots designated with critical areas or their buffers as designated in RCW 36.70A.060, or to lots in a watershed serving a reservoir for potable water if that watershed is or was listed, as of July 23, 2023, as impaired or threatened under section 303(d) of the Federal Clean Water Act (33 U.S.C. Section 1313(d)).
(5) In addition to the conditions that may be imposed by the community development director, all accessory dwelling units shall also be subject to the condition that the use shall be discontinued if:
(a) The accessory dwelling unit is substantially altered and no longer conforms with the plans approved by the community development director and the building official; or
(b) The subject lot ceases to maintain the required parking spaces outlined in MMC § 22C.130.030, Table 1.
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
Washington's HB 1337 sets a floor requiring most GMA cities to allow two ADUs per lot, and Marysville's Table 1 (MMC § 22C.185.020) follows suit: no owner-occupancy requirement, short-term rental use prohibited, size capped at 1,000 square feet or 50% of the primary home (whichever is greater) up to a hard 1,400-square-foot ceiling, and a 30-foot height limit. Subsection (2) requires the ADU's exterior materials, roof form, and window proportions to match the main house, and bars axles or a chassis outright, which rules out tiny houses on wheels as legal detached ADUs.
Violations & Fines
Installing a wheeled tiny house as a detached ADU violates § 22C.185.020(2); code enforcement can deny the permit, require removal of the axles/chassis or the unit itself, and cite the property for an unpermitted structure.
Frequently Asked Questions
Can I put a tiny house on wheels in my backyard as an ADU in Marysville?
How many ADUs can I build on one lot?
Sources & Official References
Other rules in Marysville
Compare Marysville to another location·View the Washington accessory structures overview
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Tiny Homes in Nearby Cities
How other cities in Snohomish County handle tiny homes.