Yakima County, WA Accessory Structures: Tiny Homes (2026)
Tiny home rules in Yakima County, 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
- On Foundation
- Dwelling, IRC Appendix Q
- Tiny House Size
- 400 sq ft or less
- As ADU
- Allowed under HB 1337
- On Wheels
- RV, not a residence
- RV Living
- Licensed RV parks only
Summary
A tiny home on a permanent foundation is a dwelling in unincorporated Yakima County and may use IRC Appendix Q, while a tiny home on wheels is an RV that cannot be a permanent residence in a residential zone.
A dwelling that is 400 square feet (37 m2) or less in floor area excluding lofts.
Full Breakdown
Classification decides everything in Yakima County. A tiny house built on a permanent foundation is a dwelling under the 2018 IRC (WAC 51-51), which adopts Appendix Q for tiny houses 400 square feet or less: allowing reduced ceiling heights, ladder access to lofts, and smaller stair and egress geometry. It may be the primary dwelling if the lot meets the zone's standards, or an accessory dwelling unit under HB 1337 (RCW 36.70A.681). A tiny home on wheels registered as a travel trailer or park-model RV with the Department of Licensing does not meet the state building code as a permanent home and cannot be lived in full-time on a residential lot outside a licensed RV park.
Violations & Fines
Living full-time in a tiny home on wheels on a residential lot is a zoning violation subject to daily penalties. A foundation tiny home built without a permit draws a stop-work order.
Frequently Asked Questions
Can I live in a tiny home in Yakima County?
Can I live in a tiny home on wheels on my lot?
Sources & Official References
Other rules in Yakima County
Compare Yakima County to another location·View the Washington accessory structures overview
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