Adu company — Seattle, 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

A professional company handles the heavy lifting, including architecture, engineering, permit submittals, and the actual construction labor. You need an experienced team when you want to ensure your unit is built to code, structurally sound, and completed on a predictable schedule. We act as your single point of contact, coordinating every trade and inspection so you aren't managing subcontractors yourself. We provide professional oversight from start to finish. Exact pricing confirmed free on the call.

Frequently asked in Seattle

Also serving nearby: Kirkland · Bellevue · Renton · Kent · Federal Way

All cities in Washington →

More on this: HUD ADU resources — ADU policy and financing research.

Service area details

Serving all of Seattle — population 755,078; about 8,989 residents per square mile across 84.0 sq mi. ZIP codes covered include 98101, 98102, 98103, 98104, 98105, 98106, 98107, 98108.

Neighborhoods served in Seattle: Ballard, Fremont, Capitol Hill, Queen Anne, West Seattle — and every surrounding area.