What permits do you need for a DADU?
Plan for a residential building permit and the other approvals your site needs. Zoning review, utility work, health approvals and trade permits may follow separate application paths.
Sources checked November 5, 2026. Confirm the requirements for your parcel with its permitting authority.
Confirm the application path first
Tell the permitting authority that you are proposing a detached accessory dwelling unit, not a storage building or backyard office. Ask which project type to select and whether any land-use approval is needed before or alongside the building application.
For unincorporated King County, the county’s submission guide starts with property research and then electronic application preparation. The guide identifies special conditions such as flood zones, shorelines, wetlands, slopes and lot coverage that need attention before submission. Use your own jurisdiction’s checklist when the property is inside a city.
Official guidance: King County permit application steps.
Build a coordinated document package
Use this as a preparation list, then reconcile it with the actual application requirements: a site plan; floor plans and elevations; foundation and structural information; energy-code documents; utility connections; and any drainage, access or site reports requested for the property.
Keep one current drawing set. If the building footprint changes, check whether the site, structure, drainage and utility drawings all reflect it. A coordinated package makes it easier to answer review comments without creating contradictions between sheets.
Track approvals beyond the building permit
Make an approval register with a responsible person and status for each item. Ask about electrical, plumbing, mechanical, fire, utility and clearing or grading work rather than assuming the building application includes everything.
King County’s application guide notes that septic approval or evidence of a septic application may be needed for intake. Its document library also separates materials handled by other agencies. Confirm those responsibilities early so one missing approval does not hold up the rest of the package.
Official guidance: King County building and land-use application materials.
Close the loop during construction
An issued permit starts the construction phase; it does not finish the approval process. Agree who schedules inspections, who keeps approved plans available and how the team handles changes requested in the field.
Before move-in, confirm the final inspection and occupancy requirements for the issued permits. Keep approvals, record drawings, equipment information and unresolved items together for handoff. A practical checklist follows the project through completion rather than stopping when the application is filed.
A few things to know
Is a DADU permit the same as a shed permit?
No. Describe the proposed use as a complete dwelling and follow the authority’s residential requirements.
Can I start while my application is in review?
Confirm issued permits and any prerequisites with the authority before starting the work they cover.
Keep planning
Can I Build a DADU on the Eastside? Start With Your City
Find the DADU rules for Duvall, Woodinville, Redmond, Bothell and six other Eastside communities, with local permit and eligibility guides.
Eastside DADU Timelines: Permits, Utilities and Construction
Understand the specific review milestones behind an Eastside DADU schedule, including Bothell water availability and Kirkland’s pre-approved plan path.
Can a DADU use septic or existing utilities?
Check septic capacity, sewer availability, water service and utility routes before committing to a DADU design in King County.