Not every home improvement project in Seattle requires a building permit — but many more do than most homeowners expect. Here is a comprehensive 2026 checklist to help you understand when a permit is required.
Always Requires a Permit
- Any addition to the footprint of your home
- Accessory dwelling units (ADUs and DADUs)
- Detached garages and carports over 200 sq ft
- Decks more than 30 inches above grade or attached to the house
- Structural changes — removing, adding, or moving walls
- New windows or doors that change the opening size or structural opening
- Conversion of garage, basement, or attic to living space
- New plumbing fixtures or moving existing plumbing supply lines
- New electrical panels or significant electrical service upgrades
- HVAC system replacements (heat pumps, ductwork changes)
- Fences over 8 feet
- Retaining walls over 4 feet
Generally Does Not Require a Permit
- Interior paint, wallpaper, flooring (no structural work)
- Cabinet replacement (not moving walls)
- Countertop replacement
- Replacing windows with same-size units (no structural change)
- Minor plumbing repairs (replacing faucets, toilets)
- Replacing existing light fixtures
- Decks under 30 inches above grade not attached to the house
The Gray Zone: When to Ask
Opening a wall between rooms — even a non-load-bearing wall — typically requires a permit if plumbing, electrical, or HVAC is involved. If you are unsure, the safest approach is to ask your architect or contact SDCI directly via their permit counter at SDCI.Seattle.gov.
Why Skipping Permits Is a Bad Idea
Unpermitted work creates problems at sale — buyers and lenders increasingly require permit history. Seattle can also order unpermitted work removed or require after-the-fact permitting, which is significantly more expensive than permitting upfront.
Piper Cole Architects navigates permit requirements for all project types across Seattle and the Eastside. Free consultation available. Call 425-753-6452.
Ready to Start Your Project?
Piper Cole Architects offers a free initial consultation for all project types — residential, commercial, ADU, and renovation. No obligation. Based in Kirkland, WA. Serving the entire Seattle metro area since 2000.