Local adu — 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
What is the cost of an accessory dwelling unit in Federal Way?
Can you help me find an ADU company in Federal Way?
Who are accessory dwelling unit builders in Federal Way?
How do I get an ADU permit in Federal Way?
Are accessory dwelling unit Massachusetts rules relevant in Federal Way?
What ADU services are available in Federal Way?
Who is an accessory dwelling unit contractor San Diego 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: Mirror Lake, Woodruff, The Springs, Central Federal Way, West Federal Way — and every surrounding area.
Areas we serve
Browse by state, then city.