Seattle Home Addition Permits 2026
Seattle home addition permit fees, plan review, and required inspections for 2026.
Seattle Home Addition permit basics
- Building department: Seattle Department of Construction and Inspections (SDCI)
- Department URL: https://www.seattle.gov/sdci
- Permit fee typical: $400 - $3,500 permit fee
- Plan review + approval: 10-25 business days; plan check 6-12 weeks
- Inspections required: 6-12 inspections (footing, framing, electrical, plumbing, mechanical, insulation, drywall, final)
Seattle Home Addition common issues
Setback compliance, FAR (floor-area ratio), structural review required, sewer/water capacity may need upgrade.
Seattle-specific permitting context
Seattle SDCI has strict energy code (Stretch Code). Tree ordinance affects site work. ADU streamlined permitting. WA L&I license required for all contractors.
Climate factors: Mild winters with persistent rain (moss/moisture on roofs); rare snow loads; minimal AC historically but warming trend
Washington licensing for Home Addition contractors
Washington Department of Labor and Industries (L&I) - required: $117 (initial) + $12K bond + insurance. Board: https://www.lni.wa.gov.
Mechanics lien deadline in Washington: 90 days from last work. Preliminary notice: Pre-claim notice required within 60 days of first furnishing for residential.
Seattle Home Addition sales tax
Washington sales tax: 6.5% + local (~9.3% combined avg) + 0.471% B&O. WASHINGTON TAXES CONTRACTOR LABOR. Retail Sales Tax applies to total construction contract (labor + materials) on speculative builders. Custom construction taxed differently.
Verify with the Washington Department of Revenue.
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