Looking for accessory dwelling unit companies in Seattle, WA? Call AccessoryDwellingUnit Solutions 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 involves several moving parts that shape your total budget. The biggest factor is whether you choose a prefabricated unit or a custom build on-site. Site preparation is also significant; if your land requires extensive grading, utility trenching, or foundation work, costs will climb. Your choice of finishes—like kitchen cabinetry, flooring, and siding materials—also shifts the bottom line. We help you navigate these variables to find a setup that fits your property. Exact pricing confirmed free on the call.

About this service

ADU companies offer end-to-end solutions, often handling everything from the first sketch to the final walk-through. You need these companies if you prefer a streamlined experience where one firm takes responsibility for design, permitting, and construction. They are ideal for homeowners who want to minimize the stress of managing multiple vendors and prefer a turnkey approach to adding a secondary residence to their property.

Frequently asked in Seattle

What are the disadvantages of ADUs?

While ADUs offer many advantages, potential disadvantages include the upfront construction costs and the impact on your existing yard space or privacy. You should also consider how utility hookups will work and any potential changes to your property taxes. A professional consultation in Seattle is highly recommended.

How much does an ADU cost in Washington?

The cost of an ADU in Washington, including Seattle, varies significantly based on its size, design complexity, materials used, and site preparation needs. Factors like foundation work and utility connections can also affect the overall price. A precise quote from a local contractor is the best way to determine costs.

What are the rules for ADUs in Washington?

Washington State has ADU regulations, but Seattle has its own specific local ordinances that homeowners must follow. These rules often cover aspects like minimum lot size, setbacks from property lines, and parking requirements. Working with professionals familiar with Seattle's codes is crucial for compliance.

Is an ADU allowed in Maryland?

This service is focused on providing ADU expertise and connections for projects within Washington State, particularly in cities like Seattle. Maryland has its own distinct regulations regarding Accessory Dwelling Units. If you are considering an ADU in Maryland, it's best to consult with local professionals familiar with their specific requirements.

While Washington State and Seattle may have their own unique incentive programs or financing options, they would differ from California's initiatives. Inquiring with local Seattle resources can help you find relevant support.

How do I start the ADU process in Seattle?

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: Capitol Hill, Ballard, Fremont, Queen Anne, Green Lake — and every surrounding area.