King County, WA

Common application types

• New single-family construction
• Single family remodel, addition, repair
• Residential accessory building misc. structure permits
• Commercial tenant improvements
• Clearing grading permits
• Land use short subdivision
• Land use subdivisions
• Boundary line adjustments
• Zoning code variances
• Already built construction (ABC)

New homes and additions

Single-family permits require a residential site plan with a TESC plan, a critical areas designation, residential drainage review items, Washington State Energy Code worksheets, and a water source and sewer or septic option (availability certificates, future connection certificates, a well permit or an on-site sewer application). Septic projects may need the approved septic permit and site plan, or the septic permit application, at intake. A clearing and grading permit is needed for grading within a critical area, excavation deeper than 5 ft or over 100 cubic yards, fill deeper than 3 ft or over 100 cubic yards, or more than 2,000 sq ft of new impervious surface.

ADUs and middle housing

Per the county's March 2026 ADU bulletin, properties within the Urban Growth Area may have up to two ADUs, rural area properties are limited to one (detached only on lots meeting the zone's minimum lot size), the Agriculture zone allows attached ADUs only, and ADUs are prohibited in the Forest zone. ADUs are generally limited to 1,000 sq ft of heated floor area plus 1,000 sq ft of unheated area, with urban ADUs allowed up to 1,500 sq ft heated when less unheated area is used, and no additional off-street parking is required. A notice on title identifying the accessory unit must be recorded before construction permits are approved. The 2024 Comprehensive Plan, approved December 10, 2024, directed zoning updates to allow duplexes, triplexes and ADUs more widely.

Decks, retaining walls and accessory structures

Unless the property contains critical areas, no building permit is required for storage sheds of 200 sq ft or less accessory to a house or used for agriculture, fences 6 ft or less, most retaining walls 4 ft or less, and uncovered decks 30 inches or less above ground.

Commercial tenant improvements and change of use

A tenant improvement permit covers interior changes to an existing nonresidential building but does not include new floor area or a change of use. A change of use can change required parking under KCC 21A.18 and trigger building and fire code upgrades. The county's TI guide states a licensed architect is required when the TI work area exceeds 4,000 sq ft, and applications are filed through MyBuildingPermit.com under King County, Building, Nonresidential, Tenant Improvement.

Land use review

Short subdivisions create 2 to 4 lots in rural areas or up to 9 in urban areas with a 120-day decision target, and preliminary plats cover 5 or more rural or 10 or more urban lots with a 150-day target. The county's subdivision page describes the pre-application meeting both as mandatory before filing a preliminary plat or short plat and, elsewhere, as recommended; confirm with Permitting before filing. Other land use applications include SEPA, zoning variances, conditional and special use permits, reasonable use exceptions and critical area alteration exceptions.

Corrections and review

Missing or incorrect information found at screening is communicated through the MyBuildingPermit.com portal, and incorrect or incomplete submittals are not accepted. Resubmittals are uploaded through MyBuildingPermit.com, and the county publishes a permit timelines page with current review timeframes.

Tips from SASHKOV

• Permit exemptions for sheds, decks, fences and retaining walls may not apply on parcels with critical areas.
• Confirm the parcel is in unincorporated King County and check zoning and setbacks in iMap before applying.
• A new tenant may not need a TI permit if the space already has a Certificate of Occupancy for the same use and occupancy classification with unchanged configuration and exiting.
• Food service uses need Public Health approval or a Public Health submittal with the building application.

Where to apply

Permitting authority: Department of Local Services, Permitting Division. Online submittals: MyBuildingPermit.com.