Seattle-Area ADU Service and Permit Jurisdictions

A postal address, school district or contractor service area does not identify the permit authority. The property must first be placed inside Seattle, another incorporated city or unincorporated King County. That decision controls the planning desk, code, forms, fees and utility coordination.

This hub links only to researched location pages. It does not claim that one provider covers every jurisdiction or that a city page approves a lot.

City of Seattle

Seattle SDCI maintains the City’s ADU guidance. The page explains the construction permit paths, current code topics and ADUniverse pre-approved DADU program. City projects may also involve Seattle City Light, Seattle Public Utilities and King County wastewater charges.

Use the Seattle ADU construction page for the City’s lot, plan, permit and utility sequence.

King County jurisdictions

King County contains Seattle, other incorporated cities and unincorporated territory. King County Local Services processes building and land-use permits only for unincorporated property. Its March 2026 ADU handout distinguishes urban-growth and rural rules, including the number of ADUs and possible floor-area limits.

The King County ADU guide explains how to identify the permit authority before relying on County material.

Eastside jurisdictions

Bellevue, Kirkland and Redmond are separate cities with distinct ADU and DADU resources. Bellevue adopted substantial middle-housing and ADU changes in 2025 and is developing a pre-approved plan program. Kirkland already offers pre-approved DADU plans. Redmond publishes its own residential permit and ADU materials.

Use the Eastside ADU guide before choosing a city page:

• Bellevue ADU construction
• Kirkland ADU construction
• Redmond ADU construction

North and south King County cities

Shoreline

Shoreline says its zoning code allows two ADUs on a lot and requires a building permit to construct one or convert space. Its permit checklist and tree rules are separate from Seattle’s. Read the Shoreline ADU guide.

Renton

Renton offers eight permit-ready ADU base plans from about 415 to 1,000 square feet and a pre-screening path. The plan still needs property-specific work and City review. Read the Renton ADU guide.

Burien

Burien’s current code allows up to two ADUs per lot and generally limits attached and detached ADUs to 1,000 square feet, subject to the live code and property. Read the Burien ADU guide.

Bothell

Bothell straddles King and Snohomish Counties but uses a City permit path for property inside City limits. The City publishes a residential ADU application and housing information. Read the Bothell ADU guide.

Mercer Island

Mercer Island requires an ADU permit and publishes current 2026 submittal requirements. Critical-area review and site conditions can affect the route. Read the Mercer Island ADU guide.

What changes between jurisdictions?

The project type may look similar while the local work changes. Confirm:

• number and type of ADUs allowed;
• size, height, setbacks and lot coverage;
• tree, slope, shoreline or critical-area review;
• parking and access rules;
• title, owner-occupancy or rental provisions;
• pre-approved or permit-ready plan status;
• plan-review and trade-permit process;
• water, sewer, power and stormwater authorities; and
• local fees and external-work conditions.

Rules can change after a state-law deadline or local code amendment. Link the project brief to the live official page and record the date checked.

How should provider coverage be confirmed?

Ask for the legal business name, Washington contractor-registration number and recent projects reviewed by the same permit authority. A general statement such as “serving Greater Seattle” does not establish current capacity, familiarity with the city or willingness to accept the address.

Confirm service area before sharing personal project details. Then use the builder comparison guide to review scope, registration, project proof, design responsibility, utilities, allowances, payment terms and written warranty documents.

What should every location page include?

A useful location page must do more than repeat the city name. It should identify the actual permit authority, current official resources, property constraints, plan options, utility questions, cost and schedule implications, and evidence to request from a provider.

The common feasibility, cost and timeline guides remain part of every location decision. A city page adds local facts; it does not replace the complete-project scope.

Build a dated jurisdiction record

Local ADU pages and forms change. For each project, save a short record with the parcel authority, zoning source, official ADU page, permit portal, utility providers and the date each item was checked. If staff answers a material question, save the email or meeting note and identify the proposal it addressed.

This record matters when a provider works in several cities. It lets the owner separate a current local requirement from a familiar practice used elsewhere. It also gives the designer and estimator one source list instead of forcing each participant to rediscover the jurisdiction.

When should a city page be added to this site?

A page should be published only when it serves a distinct local decision. Useful triggers include a separate permit-ready plan program, different unit or size rules, a meaningful utility or critical-area issue, measurable demand, or confirmed provider activity. A city name by itself is not enough.

The initial footprint therefore includes researched King County jurisdictions with current official sources. Additional suburbs should stay on hold until their page can add non-transferable facts and a practical project checklist. This keeps the location structure substantial while avoiding dozens of near-duplicate pages.