Adu 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
An ADU unit is simply a secondary dwelling located on the same lot as a primary residence. You might look into an ADU if you need more space for a home office, a gym, or housing for extended family. Exact pricing confirmed free on the call.
Frequently asked in Federal Way
What's the accessory dwelling unit permit cost in Federal Way?
What accessory dwelling unit services do you offer in Federal Way?
What's a detached accessory dwelling unit in Federal Way?
What is ADU housing and how can it help in Federal Way?
What are the best accessory dwelling unit options for Federal Way?
What are the accessory dwelling unit services available in Federal Way?
Can I get a quote for accessory dwelling unit construction 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: Theierry, Mirror Lake, The Heights, Lakeland, Twin Lakes — and every surrounding area.
Areas we serve
Browse by state, then city.