Accessory dwelling unit permit cost — Seattle, WA

Looking for accessory dwelling unit permit cost in Seattle, WA? Call AccessoryDwellingUnit Pros for a contact a provider — no obligation. Licensed adu builders serve Seattle and the surrounding area, and you'll get straight answers on timing and what affects the price.

Last updated: September 24, 2026

What affects the price

Building an ADU is a custom project, so costs vary based on your specific choices. Site conditions are the biggest factor; if your land requires significant grading, utility extensions, or foundation work, those expenses add up quickly. Choosing high-end finishes, custom cabinetry, or complex roof lines will also push the budget higher compared to a standard design. Prefabricated units often offer predictable costs, while custom site-built structures allow for more flexibility but can be harder to estimate upfront. Exact pricing confirmed free on the call.

About this service

Permit fees are paid to your local municipality and fluctuate based on the specific city or county where your property is located. These costs cover plan reviews, impact fees, and safety inspections required to make your new space legal and compliant. Because every jurisdiction has a different fee structure, the final amount depends on your specific town’s regulations. We help you estimate these during the planning phase. Exact pricing confirmed free on the call.

Frequently asked in Seattle

What are the best ADU companies in Seattle?

What are the requirements for an ADU permit in Seattle?

Are there specific rules for backyard ADUs in Seattle?

What is the typical cost of an ADU in Seattle?

Can I rent out my ADU in Seattle?

What makes an ADU affordable in Seattle?

What services do ADU companies offer in Seattle?

ADU companies in Seattle typically offer a comprehensive suite of services, including initial feasibility studies, architectural design, engineering, permitting assistance, and full construction management. They handle everything from site assessments to final walkthroughs, ensuring a smooth and compliant build. Some companies may also offer financing guidance or post-construction support. Engaging with a full-service provider simplifies the entire ADU development process for homeowners. They manage all aspects meticulously.

Also serving nearby: Kirkland · Bellevue · Renton · Kent · Federal Way

All cities in Washington →

More on this: HUD ADU resources — ADU policy and financing research.

Service area details

755,078residents

8,989per sq mile

8ZIP codes served

Serving all of Seattle — population 755,078; about 8,989 residents per square mile across 84.0 sq mi. ZIP codes covered include 98101, 98102, 98103, 98104, 98105, 98106, 98107, 98108.

Neighborhoods served in Seattle: Ballard, Capitol Hill, Fremont, Queen Anne, Green Lake, West Seattle — and every surrounding area.