Accessory Structures in Marysville, WA: What Residents Actually Need to Know

If you live in Marysville or are thinking about moving there, accessory structures are one of those things you probably won't think about until they affect you directly. Marysville has 7 specific rules on the books covering different aspects of accessory structures, and some of them might surprise you.

ADU Impact Fees

Marysville exempts accessory structures and city-approved accessory dwelling units from its park, recreation, open space and trail impact fees. Marysville Municipal Code § 22D.020.040(1)(b) exempts accessory structures outright, and (1)(g) exempts ADUs approved under Chapter 22C.180 MMC, even though a standalone single-family or middle-housing unit otherwise owes $1,251 per housing unit under the city's adopted fee schedule.

Key details: Accessory structures: Fully exempt under § 22D.020.040(1)(b). ADUs under Ch 22C.180: Fully exempt under § 22D.020.040(1)(g). Single-family/middle housing fee: $1,251 per housing unit. Multifamily fee: $884 per housing unit. Claim deadline: No later than building permit application.

Missing the exemption claim deadline waives it under § 22D.020.040(2), and a non-exempt project that skips payment cannot get its building permit issued under § 22D.020.030; the city may still refer formula errors to the mayor and city council for correction under § 22D.020.080(1).

If you are coming from a city with tighter rules, you will find Marysville gives residents more flexibility on adu impact fees.

Garage Conversions

Marysville lets an existing detached garage convert to an accessory dwelling unit even if it doesn't meet current setback or building-coverage requirements, waiving those two standards only.

Key details: Setback/coverage nonconformity: Allowed to remain. Applies to: Existing structures incl. detached garages. Other ADU standards: Still apply (size, height). Governing section: MMC § 22C.185.020, Table 1, Note 4.

A garage conversion that skips required building permits, or exceeds the ADU size or bedroom limits, is a Title 22C land use violation fined $150 and up per day.

Marysville is more permissive than most cities when it comes to garage conversions. That said, there are still limits.

Shed & Carport Rules

Marysville caps residential accessory structures at 80 percent of the primary home's footprint on lots under an acre, with a 5-foot side setback, a 5-foot one-story rear setback, and a 20-foot height limit unless the lot exceeds an acre.

Key details: Side setback: 5 feet. Rear setback, one-story: 5 feet. Footprint cap (under 1 acre): 80% of house footprint. Height limit: 20 ft (under 1 acre); 30 ft otherwise.

Building an accessory structure that exceeds the applicable setback, the 80 percent footprint cap relative to the primary residence, or the 20-foot height limit (30 feet where an ADU or larger lot applies) is a zoning violation reviewable by the community development director, who can also require corrective adjustments.

Tiny Homes

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.

Key details: 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).

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.

ADU Owner Occupancy

Marysville imposes no owner-occupancy requirement on the principal home or an accessory dwelling unit -- the standards table lists the requirement as 'None,' reflecting a 2023 state-law bar on local mandates.

Key details: Owner-occupancy requirement: None. Applies to: Principal home and ADU alike. Reason: HB 1337 (2023) state preemption. Table location: MMC § 22C.185.020, Table 1.

There is no owner-occupancy violation to enforce. Other ADU standards -- size, height, and setbacks -- remain enforceable as Title 22C land use violations, fined $150 and up per offense.

The rules around adu owner occupancy in Marysville lean permissive, but that does not mean anything goes.

ADU Rental Restrictions

Marysville's accessory dwelling unit code flatly bars using an ADU as a short-term rental, defined as lodging offered for a fee for fewer than 30 consecutive nights. MMC Section 22C.185.020's Table 1 pairs that ban with no owner-occupancy requirement, so an ADU can be rented long-term without the owner living on site, just never rented nightly.

Key details: Use as short-term rental: Prohibited. Short-term rental defined as: Paid lodging under 30 consecutive nights. Owner-occupancy requirement: None (long-term rental allowed). Governing table: MMC Section 22C.185.020, Table 1. First violation fine: $150 noncommercial / $250 commercial.

Advertising or operating an ADU as a nightly or short-term rental violates Table 1 of Section 22C.185.020 and is a Title 22C land use violation under MMC Section 4.02.040(3)(g): $150 for a first noncommercial violation, $250 if run as a business, rising to $300/$500 on a second violation within two years, and misdemeanor charges in Marysville municipal court for a third. The director can also order the unauthorized short-term-rental use discontinued outright.

This is not one of those rules that cities tend to ignore. Marysville actively enforces its adu rental restrictions requirements.

ADU Rules

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.

Key details: 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.

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.

The Bottom Line

Compared to many U.S. cities, Marysville gives residents more room on accessory structures. 3 of the 7 rules here are rated permissive. But permissive does not mean unregulated. There are still requirements, and the city does enforce them when violations are reported.

This guide is based on Marysville's current municipal code. Local rules can and do change, so check the individual ordinance pages for the latest details, penalties, and FAQs.