Are ADUs legal in Washington?
Yes — Washington permits ADUs by-right statewide per HB 1337 (2023). Every qualifying municipality must allow at least one ADU pathway on eligible single-family lots.
What are the size limits on an ADU in Washington?
Washington permits ADUs up to approximately 1000 square feet per HB 1337 (2023). Individual municipalities may set lower caps; verify with your city or county planning department before ordering.
Do I need a permit for an ADU in Washington?
Yes — every ADU in Washington requires a building permit issued by the city or county. The permit process typically runs 60-165 days depending on jurisdiction, complexity, and whether discretionary review is triggered.
Can I rent out my ADU in Washington?
Yes — long-term rental of an ADU is generally permitted in Washington. Short-term rental (Airbnb / VRBO under 30 days) is subject to municipal registration and may require additional permits.
Does Washington require owner-occupancy on the primary residence when I have an ADU?
No — Washington does not require owner-occupancy under state statute per HB 1337 (2023). Local ordinances may still add owner-occupancy requirements in specific cities.
What zoning districts allow ADUs in Washington?
Most Washington municipalities permit ADUs in single-family residential zones (R-1, R-2 equivalent). Washington HB 1337 (2023) requires every Washington city over 25,000 population to permit two ADUs per single-family lot by right — the most permissive by-right ADU statute in the country. Consult your city zoning code for the specific district table.
How long does an ADU permit take in Washington?
Typical ADU permit timelines in Washington run 60-165 days from application to approval. Fast-permitting counties can move in under 30 days; metro-core jurisdictions with discretionary review can extend to 150+ days.
Are there setback requirements for an ADU in Washington?
Yes — most Washington municipalities apply the same setback requirements to ADUs that apply to the primary structure (typically 5-10 feet rear and side, 15-25 feet front). Some cities apply reduced setbacks specifically for detached ADUs. Verify with your city zoning code.
Can I finance an ADU purchase in Washington?
Yes — several financing pathways cover ADU purchases in Washington: Fannie Mae HomeStyle Renovation, FHA 203(k), construction-to-perm loans, HELOC on the primary residence, and cash. Check with modular-friendly lenders like 21st Mortgage, Cascade Financial, and Triad Financial for the Washington-specific product.
What's the difference between an ADU and a JADU in Washington?
The JADU (Junior ADU) category originated in California and is not a distinct legal category in Washington. Most Washington municipalities regulate internal conversions and detached units under a single ADU/accessory apartment definition.