Accessory dwelling units adus — Seattle, WA

Last updated: September 24, 2026

What affects the price

Building an ADU is a custom project, so costs vary based on your specific choices. Site conditions are the biggest factor; if your land requires significant grading, utility extensions, or foundation work, those expenses add up quickly. Choosing high-end finishes, custom cabinetry, or complex roof lines will also push the budget higher compared to a standard design. Prefabricated units often offer predictable costs, while custom site-built structures allow for more flexibility but can be harder to estimate upfront. Exact pricing confirmed free on the call.

About this service

ADUs are secondary housing units that provide extra space for guests, family, or renters. You should consider an ADU if you want to increase your property value or need more living space without moving. Prices typically vary based on the square footage, the quality of construction, and necessary utility upgrades for your specific lot. Exact pricing confirmed free on the call.

Frequently asked in Seattle

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

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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, Capitol Hill, Fremont, Queen Anne, Green Lake, University District — and every surrounding area.