City of Seattle, WA

Common application types

• Construction Permit - New Building, Single-Family Residential or Duplex
• Construction Permit - Addition or Alteration
• Construction Permit - Subject-to-Field-Inspection
• Construction Permit - Establishing Use
• Tenant Improvement Permit (Blanket)
• Grading Permit
• Demolition Permit - Building
• Land Use / Master Use Permit - Plat
• Land Use / Master Use Permit - Environmentally Critical Areas (ECA)
• Land Use / Master Use Permit - Variance

New homes and additions

New houses and duplexes use the Construction Permit - New Building; additions and remodels use an addition/alteration permit, or an STFI permit when small. The new single-family checklist calls for architectural and structural plans, a site/plot plan survey, Drainage and Wastewater Control plans, Construction Stormwater Control and Soil Amendment plans and an identified Energy Code compliance path with a UA calculation (prescriptive path) and a heating equipment sizing calculation. A drainage report is required at 5,000 sq ft or more of new plus replaced hard surface, with drainage plans for those projects stamped by a licensed civil engineer, and a licensed topographic survey with 2 ft contours is required when the project is within 2 ft of the height limit. A pre-application site visit is required for most new construction and grading applications, and for any project that disturbs more than 750 sq ft of land or any land on a site with certain environmentally critical areas.

ADUs and middle housing

Seattle's interim HB 1337 and HB 1110 compliance ordinances (Ord. 127211 and 127219) took effect June 30, 2025. City Council passed permanent middle housing legislation (Council Bill 120993) on December 16, 2025, effective in mid-January 2026; SDCI cites Ordinance 127376 for the updated Neighborhood Residential (NR) code. In NR zones the allowed number of units, including ADUs, is the greatest of one unit per 1,250 sq ft of lot area (one per 600 sq ft for stacked flats), 4 units, or 6 units within a quarter mile of a major transit stop or with at least two affordable units, with reductions on lots with environmentally critical areas. A lot may have up to two ADUs, limited to 1,000 sq ft of gross floor area with up to two bedrooms or 1,200 sq ft with three or more, and ADUs require no off-street parking. NR lot coverage is limited to 50 percent.

Decks, retaining walls and accessory structures

Decks need a permit when more than 18 inches above ground, on a roof, or in an ECA; most use an STFI permit, with an addition/alteration permit required above 8 ft high, over 750 sq ft, with beams 14 ft or longer, or with a solid surface. Sheds with a roof footprint of 120 sq ft or less that are single-story, detached, not in or near an ECA and used only for storage or similar uses need no permit. Retaining walls and rockeries 4 ft or lower (bottom of footing to top) that are not on an ECA parcel and will not damage adjoining property need no construction permit.

Commercial tenant improvements and change of use

A change of use always requires a building permit, and the change is measured against the last legally permitted use in SDCI records. Alterations without a change of use are treated as tenant improvements, and some small projects where the established use stays the same can be processed as STFI permits. SDCI states projects valued over $75,000 need construction documents stamped by a Washington-licensed architect or engineer, and some projects need a stamp regardless of value.

Land use review

Land use decisions run through Master Use Permits, including SEPA, ECA, variance, shoreline and plat review. Short subdivisions create up to 9 parcels, full subdivisions 10 or more, and a unit lot subdivision uses the short or full process and must be preceded by a land use or construction permit approving the specific residential development. Pre-submittal conferences are recommended, not required, for complex projects such as ECA or shoreline sites and full subdivisions.

Corrections and review

Applicants receive an email when corrected or additional documents can be uploaded to the portal. SDCI's initial review guide lists targets of 1 to 2 weeks for simple projects and 8 to 12 weeks for complex projects, and SDCI states it can usually take in a complete application within two to three weeks of upload.

Tips from SASHKOV

• Upload all application documents by 7 AM on the day of the electronic intake appointment; fees not paid within 48 hours of the application being deemed complete result in a rejected intake.
• Exterior work on sites with environmentally critical areas often does not qualify for an STFI permit.
• Retaining walls of any height on a parcel with an ECA need a permit unless specific requirements or an exemption are met.
• Decks more than 36 inches above ground count toward lot coverage, which is limited to 50 percent in Neighborhood Residential zones.

Where to apply

Permitting authority: Seattle Department of Construction and Inspections (SDCI). Online submittals: Seattle Services Portal.