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DATASET / SEATTLE PERMITS

Seattle ADU Permit Process

The full Seattle, WA ADU permit pipeline from pre-application through certificate of occupancy. 5 phases, current fees, review department contacts.

Total timeline
25–43 weeks
Total city fees
$5,000–$13,500

Last updated 2026-05-15

  1. PHASE_01Intake & Application
    Details →
    Timeline
    1–2 wk
    Fees
    $500–$1,500
    Department
    SDCI
  2. PHASE_02Screening & Routing
    Details →
    Timeline
    1–2 wk
    Fees
    —
    Department
    SDCI
  3. PHASE_03Plan Review (Land Use + Building)
    Details →
    Timeline
    6–10 wk
    Fees
    $3,000–$8,000
    Department
    SDCI
  4. PHASE_04Permit Issued
    Details →
    Timeline
    1–1 wk
    Fees
    $1,500–$4,000
    Department
    SDCI
  5. PHASE_05Construction Inspections + CO
    Details →
    Timeline
    16–28 wk
    Fees
    Included
    Department
    SDCI
NAV_GRAPH / Local data

Seattle permit resources

FAQ

Frequently asked

  • What is the current Seattle, WA ADU permit timeline?

    Median Seattle ADU permit issuance from clean submittal is 8–16 weeks in 2026. That breaks down as: intake + completeness check (5–10 business days), first review cycle (4–7 weeks across building, planning, side-sewer, addressing, drainage as applicable), corrections back to us (1–2 weeks), second review (2–4 weeks), then issuance. Pre-application meetings shave one full cycle on average. The fastest Seattle ADU we have closed in 2025 was 6.5 weeks on a catalog plan with a pre-app; the slowest was 22 weeks because of a side-sewer easement title issue — not a planning issue.

  • What reviews are required for an ADU in Seattle?

    Standard Seattle ADU review touches building, planning (zoning, lot coverage, setbacks), addressing, side-sewer (or septic where applicable), water availability, drainage review (if impervious exceeds threshold), and energy review (IECC R406 worksheet). Critical-areas review triggers if your lot is mapped for steep slope, wetland, riparian, or landslide hazard. SEPA review is rare for a single ADU but possible if other land-use actions are pending on the same parcel. Each review runs in parallel, not sequentially, which is why pre-app meetings matter.

  • What gets Seattle ADU permits rejected on first review?

    Top six Seattle reviewer redlines we see: (1) IECC R406 envelope worksheet missing or calculations not matching plan assemblies; (2) side-sewer not shown on site plan with slope and invert; (3) lot coverage math omits roof overhangs (count to drip line in Seattle); (4) Fire separation between primary and ADU walls insufficient when separation < 5 ft; (5) glazing U-factor or SHGC on schedule doesn't match window NFRC labels; (6) drainage report missing when impervious increase is over the threshold. We catch all six in our QA before submittal.

  • Can I expedite the Seattle ADU permit?

    Seattle does not offer formal paid expedite for residential ADUs, but the practical accelerators are: catalog plans (reviewers see familiar details and move fast), complete drainage report at submittal, pre-app meeting on file, and using a contractor whose past submittals were clean. We track our own correction count per submittal; clean sets average 1.2 review cycles in Seattle versus the city-wide 1.8 average. Pre-app meetings are free and currently scheduling 3–4 weeks out — book one before drawings start.