Seattle ADU Permit Fees & Cost Calculator
Seattle allows ADUs and SDCI says ADUs are permitted through a construction addition/alteration permit or a permit to establish use for legalization; SDCI also states that some standards do not apply, including parking, street improvements, and mandatory housing affordability contributions. Exact current fee amounts were not clearly published in the official ADU page, so the fee items below rely on official fee-schedule pages and manual verification is still needed.
Free ADU fee calculator
Estimate local ADU fees
Step 1 of 5: Location
The calculator uses staged city data from the ADUFee database with visible confidence levels and dated source tracking.
Fee overview
Do not treat any non-official fee estimates from search results as authoritative.
Seattle ADU costs in third-party guides often mix construction costs with permitting and utility charges; those figures are not city fee schedules.
The official ADU page indicates some common development standards do not apply to ADUs, so impact-fee treatment may differ from other residential projects and should be verified against the current SDCI fee schedule.
The request is for city-level ADU permit and pre-development fee data for Seattle, Washington.
Only official Seattle sources were used for fee structuring because the provided results did not include a direct city fee schedule page with exact amounts.
Fees that depend on valuation, scope, or utility design were left null because exact published amounts were not available in the official source provided.
FAQs
Are Seattle ADU fee estimates official?
No. ADUFee.com provides planning estimates only. Final fees are set by the city, utility providers, school district, and other agencies.
What sources are used for Seattle?
The database stores city, state, utility, school, county, and other source links where available. Each estimate should still be verified locally.
Can ADU fees vary within Washington?
Yes. Permit, utility, school, inspection, and impact fees can vary by jurisdiction, parcel, project size, utility provider, and local interpretation.