Cost of accessory dwelling unit — Federal Way, WA
Last updated: September 24, 2026
What affects the price
Building an ADU involves several moving parts that shape your total investment. The final figure depends heavily on whether you choose a prefab unit or a custom build from the ground up. Site conditions are another major factor; if your property requires extensive grading, utility trenching, or foundation work, costs will climb. You also have to consider your choice of finishes, like high-end appliances or custom cabinetry. Navigating local permit fees and impact assessments also adds to the total.
About this service
Building an ADU involves several variables that shift the total investment. Your site conditions, the type of foundation, and the quality of finishes you choose will dictate whether you land on the lower or higher end of the spectrum. Because every lot is unique, we provide a breakdown of your specific project requirements to ensure full transparency. Exact pricing confirmed free on the call.
Frequently asked in Federal Way
What accessory dwelling unit services are available in Federal Way?
Accessory dwelling unit services in Federal Way, Washington, cover the entire process of adding a secondary dwelling to your property. This includes initial design, navigating local permits with the city of Federal Way, and full construction. They are committed to delivering high-quality ADUs. They ensure your project meets all Washington state and Federal Way regulations. They'll guide you every step of the way.
Where can I find accessory dwelling unit builders near me in Federal Way?
What is the accessory dwelling unit cost in Federal Way?
Who is the best accessory dwelling unit contractor in Federal Way?
What are the benefits of an ADU near me in Federal Way?
Are there affordable ADU options in Federal Way?
What's involved in getting an ADU quote in Federal Way?
Also serving nearby: Tacoma · Kent · Renton · Seattle · Bellevue
More on this: HUD ADU resources — ADU policy and financing research.
Service area details
Serving all of Federal Way — population 97,701; about 4,375 residents per square mile across 22.3 sq mi. ZIP codes covered include 98003, 98023, 98063, 98093.
Neighborhoods served in Federal Way: The Commons, Woodcreek, Chase Lake, Mirror Lake, Allenmore — and every surrounding area.
Areas we serve
Browse by state, then city.