Yakima's Accessory Structures: The Rules That Matter

Every city handles accessory structures a little differently. In Yakima, Washington, there are 5 distinct rules that residents and property owners should be aware of. Some are stricter than what neighboring cities enforce, and others are more relaxed. Here is what you need to know.

ADU Rules

Yakima YMC 15.09.045 governs Accessory Dwelling Units (ADUs) — attached, garage-mounted, or detached stand-alone — with a 1,000 sq ft maximum floor area, exterior design that matches the primary dwelling, and one ADU per single-family lot. Washington HB 1337 (2023, RCW 36.70A.680-696) now requires Yakima as a GMA-planning city to allow at least two ADUs per single-family lot, eliminate owner-occupancy requirements, and waive off-street parking minimums within 0.5 mile of major transit. Yakima must update YMC 15.09.045 to comply by mid-2025 (six months after its next periodic GMA comprehensive plan update).

Key details: Current Code: YMC 15.09.045 Accessory Dwelling Units. Current Size Cap: 1,000 sq ft floor area. Current ADUs Per Lot: 1 (transitioning to 2 per HB 1337). State Mandate: WA HB 1337 (RCW 36.70A.680-696) — 2 ADUs per lot. HB 1337 Compliance Deadline: Mid-2025 (6 months after next GMA periodic update).

Building or occupying an ADU without a Yakima building permit and final Certificate of Occupancy is enforced by the Yakima Code Administration Division under YMC Title 11 and RCW 19.27 with stop-work orders, civil penalties, and order to vacate. Zoning violations (exceeding the 1,000 sq ft cap, missing matching exterior design, violating accessory-structure setbacks) are enforced by Planning under YMC 15.09. After HB 1337 compliance is adopted, Yakima cannot enforce repealed provisions inconsistent with state law.

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

Garage Conversions

Converting a Yakima garage to habitable space requires a building permit and electrical permit from the Yakima Code Administration Division under the 2018 Washington State Building Code (RCW 19.27). A garage-to-ADU conversion that adds a kitchen and separate entrance falls under YMC 15.09.045 ADU rules — 1,000 sq ft max floor area (HB 1337 may raise the cap), matching exterior, and accessory-structure setbacks. Per WA HB 1337 (RCW 36.70A.680), Yakima must allow garage-conversion ADUs without owner-occupancy mandates and without off-street parking replacement within 0.5 mile of major transit.

Key details: Building Permit: Required (change of occupancy U→R-3). Electrical / Mechanical / Plumbing: Separate permits per WAC 51-50. Building Code: 2018 Washington State Building Code (RCW 19.27). Energy Code: 2021 WA State Energy Code (RCW 19.27A). ADU Trigger: Kitchen + separate entrance.

Building without permits triggers a Yakima Code Administration stop-work order, double permit fees per WAC 51-50, and possible removal order. Creating an unpermitted second dwelling unit (kitchen + separate entrance) without YMC 15.09.045 ADU approval is a zoning violation under YMC 15.09, enforced by Planning and Code Administration with civil infractions, daily penalties, and stop-use orders. Provisions inconsistent with WA HB 1337 (owner-occupancy mandate, excessive parking replacement) are unenforceable per RCW 36.70A.020.

Tiny Homes

A tiny home on a permanent foundation in Yakima is treated either as a primary single-family dwelling (must meet YMC 15.03 zoning standards for the zone) or as an Accessory Dwelling Unit under YMC 15.09.045 (1,000 sq ft cap, matching exterior, accessory-structure setbacks). The 2018 Washington State Building Code (RCW 19.27 + WAC 51-50) adopts IRC Appendix Q (Tiny Houses) — allowing reduced ceiling heights, ladder access to lofts, and small-stair geometry. Tiny homes on wheels (THOWs) registered as RVs cannot serve as a permanent residence in residential zones. WA HB 1337 (RCW 36.70A.680) requires Yakima to allow ADU-style tiny homes including detached units.

Key details: Building Code: 2018 WSBC + IRC Appendix Q (Tiny Houses). Tiny Home as Primary Dwelling: Permitted on permanent foundation if zone standards met. Tiny Home as ADU: Permitted under YMC 15.09.045 (1,000 sq ft cap). HB 1337 ADU Mandate: 2 ADUs per single-family lot required statewide. Tiny Home on Wheels (THOW): Not permitted as residence (RV registration).

Living in a THOW or RV in a Yakima residential zone is a zoning violation under YMC 15.04 and YMC Ch. 6.88, enforced by Yakima Code Administration and Planning with notice of violation, civil infractions, daily penalties, and order to vacate. Site-built tiny homes built without permits trigger a Yakima Code Administration stop-work order, double permit fees per WAC 51-50, and possible removal order.

Shed Rules

Yakima YMC 15.05 Table 5-1 places detached residential accessory structures (sheds, detached garages, carports) at typically 5 ft minimum side and rear setbacks in SR, R-1, R-2, and R-3 zones, with no front-yard setback closer than the principal building. The 2018 Washington State Building Code (RCW 19.27) — based on 2018 IBC/IRC — exempts one-story detached residential accessory structures up to 200 sq ft from a building permit, provided no electrical, plumbing, or mechanical systems are added. Sheds over 200 sq ft, or any shed with utilities, require a Yakima Code Administration building permit.

Key details: Code Reference: YMC 15.05 Table 5-1 (setbacks) + WSBC 2018. Side / Rear Setback: 5 ft minimum (typical residential zones). Behind Principal Building: Generally required (or per zone front setback). Permit-Exempt Size: ≤200 sq ft, no utilities (WSBC / IRC R105.2). Permit Fee Range: $100-$300 (Yakima Code Administration).

Building without a required Washington State Building Code permit triggers a Yakima Code Administration stop-work order, double permit fees per WAC 51-50, and potential removal order. Zoning setback or coverage violations are enforced by Yakima Planning under YMC 15.05 and YMC Ch. 6.88 with civil infractions, daily penalties, and abatement remedies in Yakima Municipal Court.

Yakima is more permissive than most cities when it comes to shed rules. That said, there are still limits.

Carport Rules

Yakima YMC 15.05 Table 5-1 sets detached carport setbacks at typically 5 ft minimum side and rear in SR, R-1, R-2, and R-3 zones. Attached carports follow the principal-building setbacks for the zone. Construction requires a building permit from the Yakima Code Administration Division under the 2018 Washington State Building Code (RCW 19.27) with engineered anchorage for Yakima Valley wind loads (~90-100 mph) and Seismic Design Category D1. Enclosing a carport with walls converts it to a garage and requires a new permit with fire-separation, garage door, and vehicle barrier per IRC R302.6.

Key details: Code Reference: YMC 15.05 Table 5-1 + WSBC 2018. Side / Rear Setback (detached): 5 ft minimum (typical residential zones). Behind Principal Building: Generally required. Attached Carport: Principal-building setbacks apply. Building Permit: Required (Yakima Code Administration).

Building without a Washington State Building Code permit triggers a Yakima Code Administration stop-work order, double permit fees per WAC 51-50, and potential removal order. Zoning setback violations are enforced by Yakima Planning under YMC 15.05 and YMC Ch. 6.88 with civil infractions and daily penalties.

Yakima is more permissive than most cities when it comes to carport rules. That said, there are still limits.

The Bottom Line

Compared to many U.S. cities, Yakima gives residents more room on accessory structures. 3 of the 5 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 Yakima's current municipal code. Local rules can and do change, so check the individual ordinance pages for the latest details, penalties, and FAQs.