ADU Permit Requirements in Yakima County, WA
Yakima County Building and Fire Safety Division issues building, electrical, mechanical, and plumbing permits for unincorporated Yakima County in eastern Washington. Note that the Town of Naches and 13 other incorporated cities (Yakima, Union Gap, Selah, Moxee, Tieton, Zillah, Toppenish, Wapato, Sunnyside, Grandview, Mabton, Granger, Harrah) run their own building offices; parcel verification is required for addresses inside incorporated limits. Codes in force: 2021 Washington State Residential Code (WSRC), 2021 WSBC, 2021 WSMC, 2021 WUPC, 2021 WSEC with Washington State Building Code Council amendments effective March 15, 2024. Design criteria: 110 mph wind, Seismic Design Category C or D-1 (local verification), Climate Zone 5B (eastern WA cold-dry), ground snow 25 psf at valley floor (parcels over 70 psf require engineering), frost depth 24 inches. All contractors must be registered with WA Department of Labor and Industries (L&I), bonded, and insured. Owner-builder permits allowed for primary residence with affidavit. Septic (OSS) via Yakima Health District at (509) 575-4040. Water rights and well permits via WA Department of Ecology. Accela online permit portal. Inspections direct line (509) 574-2370.
By Joey, Founder · Last verified April 22, 2026 · How we research →
When you need a ADU permit in Yakima County
A detached accessory dwelling unit (ADU) requires building, plumbing, electrical, and mechanical permits. Confirm ADUs are allowed in the county zoning code (YCC Title 15A) before applying. Septic capacity must be reviewed by Yakima Health District at (509) 575-4040 if the property is on septic.
An attached ADU (in-law suite, garage conversion with kitchen) requires building, plumbing, and electrical permits. Septic capacity must be reviewed by Yakima Health District at (509) 575-4040 if on septic.
ADU Permit Costs: Yakima County vs. Nearby
| City | Estimated Fee |
|---|---|
| Yakima County | N/A |
| Seattle | $750 – $7,500 |
| Spokane | $750 – $7,500 |
| Tacoma | $750 – $7,500 |
Fees shown are estimates based on local building code data. Actual fees may vary based on project scope and valuation. See all Yakima County permit costs →
Zoning & HOA Considerations
ADU regulations vary dramatically by state and city. Many states (CA, OR, WA) have preemption laws that override local zoning restrictions. Check both state law and local zoning before designing.
If you live in an HOA community: hOAs have traditionally restricted ADUs, but state preemption laws in CA, OR, WA, and other states now limit HOA authority over ADUs. Check your state's ADU laws, your HOA may not be able to block construction even if CC&Rs appear to prohibit it.
Estimated Project Timeline in Yakima County
Here's a typical timeline for a adu project in Yakima County, WA:
Timeline is based on Yakima County's typical about 4 weeks permit processing time. Actual timelines vary by project complexity, completeness of application, and current department workload.
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Frequently Asked Questions
Contact Yakima County's building department for current ADU permit fee information. Fees typically vary based on project scope and valuation.
It depends on the specifics of your project. Some smaller ADU projects may be exempt from permit requirements, while larger ones typically require a permit. Use our free lookup tool to check your specific situation.
Working without a required permit in Yakima County can result in fines, stop-work orders, being required to remove completed work, and complications when selling your home. It's always best to check first.
Typical approval time for ADU permits in Yakima County is about 4 weeks. More complex projects may take longer if plan review is required.
If you live in an HOA community, you may need architectural review approval in addition to a building permit. HOA rules and city building codes are separate, you may need to satisfy both. Review your CC&Rs and submit to your HOA's architectural review committee before starting work.
Learn More About ADU Permits
Read our complete guide covering permit requirements, costs, common exemptions, and the application process.
Read ADU Guide →