ADU Permit in Seattle, Washington
- Permit Required
- Unknown
- Authority
- City of Seattle
- Last Verified
- 2026-09-29
What the official source says
“While some property may be large enough to have four or more units, only two of them may be ADUs.”
seattle.gov
“In most cases, you can get your permit in just 2-6 weeks.”
seattle.gov
Verify before you build — primary source for this page: https://www.seattle.gov/construction-and-inspections/permits/common-projects/accessory-dwelling-units
Permit Requirements
While some property may be large enough to have four or more units, only two of them may be ADUs.
Application Process
Processing time: 2-6 weeks.
Washington statewide rule
The state rule is the baseline everywhere in Washington; Seattle can add stricter local requirements.
- “(c) The city or county must allow at least two accessory dwelling units on all lots that are located in all zoning districts within an urban growth area that allow for single-family homes in the following configurations:” source: app.leg.wa.gov
How to apply
- Confirm the rules for your address with City of Seattle — the official sources on this page are the place to start.
- Prepare a simple site plan or drawing showing where the adu work goes and its size.
- Submit the application and pay the permit fee.
- Schedule the required inspections and keep the approved permit on site.
Building Department
City of Seattle
Official Sources
FAQ
How much does a adu permit cost in Seattle, and how long does it take?
The fee is set by the local permit office. Processing time: 2-6 weeks.
Where do I apply for a adu permit in Seattle?
Applications go to City of Seattle.