Adu permit — 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
Obtaining an ADU permit is the legal process of getting city approval for your secondary structure. You need this documentation before any construction begins to ensure your build meets local safety and zoning codes. The permitting phase can involve architectural plans and engineering reviews. Fees and design costs for this stage typically add several thousand dollars to your project. Exact pricing confirmed free on the call.
Frequently asked in Federal Way
What does accessory dwelling unit mean in Federal Way?
What is the permit process for an accessory dwelling unit in Federal Way?
What are the costs associated with building an accessory dwelling unit in Federal Way?
Can I build a detached accessory dwelling unit in Federal Way?
What are the best ADU options for my property in Federal Way?
How do I find an accessory dwelling unit contractor in Federal Way?
What is accessory dwelling unit construction like 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, Woodmont, Star Lake, Lake Dolloff — and every surrounding area.
Areas we serve
Browse by state, then city.