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.
Frequently asked in Federal Way
Can I find an accessory dwelling unit contractor in Federal Way?
What are the steps for ADU building in Federal Way?
What are the financing options for an ADU in Federal Way?
What is an emergency ADU in Federal Way?
Can I get an accessory dwelling unit contractor in San Diego if I'm in Federal Way?
What are the requirements for ADU construction in Federal Way?
What is ADU housing 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, Mirror Lake, Kilo, Woodmont, Northlake — and every surrounding area.
Areas we serve
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