Addition permits in City of Seattle: fees, timeline & requirements (2026)
Everything you need to know about pulling a home addition permit in City of Seattle, Washington — when one is required, what it costs, how long review takes, what documents are required, and which inspections you can expect. Cited to Seattle Department of Construction & Inspections (SDCI).
Permit required?
Yes — see threshold below
Permit fee
Construction Permit (Addition/Alteration). Pay 75% of plan-review + permit fees at application acceptance. See SDCI 2026 Fee Estimator.
Review timeline
—
When does a home addition need a permit in City of Seattle?
Any additional floor area requires Construction Permit (Addition or Alteration). Plan review required. ECA + lot coverage + setback compliance verified at intake.
Required submittals
- architectural plans
- structural calcs
- WSEC compliance form
- site plan w/ setbacks + lot coverage
- survey if near setback or in ECA
Inspection sequence
- footing
- foundation
- framing
- rough-in (electrical/plumbing/mechanical)
- insulation
- drywall
- final
Contractor specialties needed
general, electrical-01-or-02, plumbing, mechanical
Notes & caveats
Full structural plan review. Lot coverage limits apply (NR zones: 35% or 1,000sf + 15% for small lots). Energy code applies to new conditioned space.
How to apply
- 1. Confirm your parcel's zoning & overlays. Run an address lookup on the main permits page — we'll pull your specific lot polygon, zoning, setbacks, and any shoreline/ECA/historic overlays.
- 2. Assemble submittals (5).
- 3. Submit through the city portal: Seattle Department of Construction & Inspections (SDCI) ↗
- 4. Track review (typical: —). Respond to reviewer comments promptly.
- 5. Pay issuance fees (Construction Permit (Addition/Alteration). Pay 75% of plan-review + permit fees at application acceptance. See SDCI 2026 Fee Estimator.) and pick up the permit. Inspection card travels with the job.