Detached ADU (DADU) Permits in City of Seattle
A standalone backyard cottage with its own foundation, roof, and exterior. Maximum flexibility on layout; highest construction cost. State law bars a city maximum below 1,000 sq ft of gross floor area, except on lots with critical areas (RCW 36.70A.681).
Drops the placement canvas on your parcel for detached adu (dadu) scope. Live setback + coverage + easement checks; packet generation when you’re ready.
Permit fees in City of Seattle
Fee schedule not yet aggregated — check the City of Seattle fee schedule directly.
City of Seattle fee scheduleConstruction Permit (Addition/Alteration). Pay 75% of plan-review + permit fees at application acceptance. See 2026 Fee Estimator + Director's Rule 5-2025. Pre-approved DADU plans waive most plan-review fees.
Review timeline
Timeline not yet aggregated — the per-parcel page shows the live estimate.
What a DADU permit packet contains
- A1.1 — Site plan with rotated footprint, setbacks, coverage
- A2.1 — Floor plan with rooms, openings, egress
- A3.1 — Elevations (all four faces, dim strings)
- A4.1 / A4.2 — Foundation + framing plans
- A5.1 — Wall section with WSEC R-values
- A6.0 — Glazing schedule (NFRC U-factor + SHGC)
- Filled application forms (city-specific)
- Manual J energy compliance report