Best accessory dwelling unit — Portland, OR

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

Frequently asked in Portland

Also serving nearby: Vancouver · Beaverton · Gresham · Hillsboro · Salem

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

Service area details

Serving all of Portland — population 630,498; about 4,723 residents per square mile across 133.5 sq mi. ZIP codes covered include 97201, 97202, 97203, 97204, 97205, 97206, 97207, 97208.

Neighborhoods served in Portland: Pearl District, Hawthorne, Alberta Arts District, Laurelhurst, Sellwood-Moreland, Downtown Portland — and every surrounding area.