Building permits in King County, Washington
Find the right authority before you build. King County permitting follows Washington law — here is exactly who issues the permit and where to start.
County + cities (mixed)
King County Dept. of Local Services (unincorporated) / City of Seattle for in-city
In unincorporated King County, building permits are issued by the King County Department of Local Services. Within Seattle, Bellevue, and other incorporated cities, the city building department issues the permit instead.
Permit cheat-sheet (Washington rules)
| Project | Permit? | Authority | Typical fee | Timeline | Go / No-Go | Key notes |
|---|---|---|---|---|---|---|
| 🏠 Accessory Dwelling Unit (ADU) | Permit required | city | Valuation-based; Seattle SDCI issue fees scale with project value (no flat state fee). | Seattle pre-approved DADU plans ~2–6 weeks; custom plans longer. | Generally allowed | Washington HB 1337 (2025) mandates ADUs; Seattle also allows two ADUs per lot. Owner-occupancy and extra parking are not required in Seattle. Exempt: Statewide HB 1337 (eff. 2025) allows ≥1 ADU per lot; Seattle allows up to 2 ADUs. |
| 🪵 Deck / Porch | Conditional | city | Valuation-based; fee set by the issuing city. | Simple decks may be Subject-to-Field-Inspection; standard review 4–8 weeks. | Generally allowed | Attached decks and decks over 30 in above grade always require a permit. Exempt: Freestanding decks ≤30 in above grade and ≤200 sq ft are commonly exempt. |
| 🧱 Fence / Wall | Conditional | city | Often no building-permit fee when under the height threshold; zoning rules still apply. | Typically no building permit below threshold; review only if over height. | Generally allowed | Corner lots have sight-triangle limits; Environmentally Critical Area (ECA) lots need a pre-application site visit. Exempt: Seattle: no building permit for fences < 8 ft; Spokane generally requires a permit for new/replacement fences. |
| 🛖 Shed / Outbuilding | Conditional | city | Valuation-based when a permit is required; many small sheds are exempt. | Exempt sheds need no review; others often Subject-to-Field-Inspection. | Generally allowed | Lot-coverage and stormwater rules still apply even when a permit is not required. Exempt: Seattle: one-story detached accessory building <120 sq ft roof area on slab-on-grade exempt; Spokane <200 sq ft exempt. |
| 🪜 Basement Finish | Permit required | city | Valuation-based; includes trade permits (electrical, plumbing). | Standard review 4–8 weeks. | Generally allowed | Bedrooms must have an emergency egress window (≥5.7 sq ft opening). Exempt: Cosmetic-only finishing (paint, flooring) is exempt. |
| 🚗 Garage / Carport | Permit required | city | Valuation-based; includes trade permits. | New structure review; complex projects 8–16 weeks. | Generally allowed | Attached and detached garages require a full building permit and plan review. Exempt: No exemption — a new garage is a new structure. |
| ☀️ Rooftop Solar PV | Permit required | city | Building + electrical permits; Seattle combined fees typically a few hundred dollars. | Seattle Solar Express: same-day for standard residential PV <30 kW (RCW 64.40 / HB 1117). | Generally allowed | Washington HB 1117 requires expedited solar permitting; HOA solar restrictions are limited by RCW 64.38.055. Exempt: No size exemption; systems >30 kW use the standard path. |
| 🌡️ HVAC Replacement | Permit required | city | Mechanical (trade) permit; fee set by city. | Trade permits often issued quickly; same-day in many cases. | Generally allowed | New equipment must meet the Washington State Energy Code (WSEC-R). Exempt: No exemption for equipment replacement. |
| 🍳 Kitchen Remodel | Conditional | city | Valuation-based when structural/plumbing/electrical work is included. | Standard review 4–8 weeks for permitted scopes. | Generally allowed | Verify whether walls are load-bearing before any layout change. Exempt: Cabinet/countertop swap in the same layout is exempt. |
| 🛁 Bathroom Remodel | Conditional | city | Valuation-based when plumbing is relocated. | Standard review for permitted scopes. | Generally allowed | Ventilation must meet code; exhaust to the exterior is required. Exempt: Fixture-for-fixture swap in place is often exempt. |
| 🏗️ Room Addition | Permit required | city | Valuation-based; includes trade permits. | Complex review 8–16 weeks. | Generally allowed | Middle-housing reforms (HB 1110) may allow more units by right; check zoning. Exempt: No exemption — any new conditioned footprint requires a permit. |
| 🪟 Window / Door Replacement | Conditional | city | Usually no fee for in-kind swap; permit needed if opening is enlarged. | In-kind swaps typically need no review. | Generally allowed | Replacement windows should meet U-factor requirements when the energy code is triggered. Exempt: Same-size, in-kind replacement is generally exempt. |
| 🏘️ Roof Replacement | Conditional | city | Often Subject-to-Field-Inspection or exempt for same-footprint re-roof. | STFI re-roofs can be approved same-day. | Generally allowed | Snow-load and seismic detailing apply in eastern WA (Spokane). Exempt: Same-material, same-slope re-roof often exempt/STFI. |
| 🅿️ Driveway / Parking Pad | Conditional | city | Building permit often not required; curb-cut/right-of-way work is separate. | Right-of-way permits reviewed by the city/utility. | Generally allowed | A separate right-of-way or utility permit is usually needed to cut the curb. Exempt: Seattle: driveways <18 in above grade exempt from building permit; Spokane <30 in exempt. |
| 🏊 Swimming Pool / Spa | Permit required | city | Valuation-based; includes barrier/fencing review. | Standard review; varies by city. | Generally allowed | Washington adopts the International Swimming Pool & Spa Code (WAC 51-50-3109); barrier fencing is mandatory. Exempt: No exemption — pools/spas require a permit (incl. most above-ground). |
| 🧱 Retaining Wall | Conditional | city | Valuation-based when over the height threshold. | Over-threshold walls need plan review. | Generally allowed | Walls in Environmentally Critical Areas need a pre-application site visit. Exempt: Walls <4 ft from bottom of footing are generally exempt. |