Accessory dwelling unit construction cost

Looking for accessory dwelling unit construction cost in Portland, OR? Call AccessoryDwellingUnit Experts for a contact a provider — no obligation. Licensed adu builders serve Portland and the surrounding area, and you'll get straight answers on timing and what affects the price.

Last updated: September 24, 2026

What affects the price

Building an ADU is a major project, and the final bill depends on a few key things. Site prep is a big factor; if your land is sloped or needs extensive utility connections, costs go up. The materials you choose—from siding to kitchen finishes—also change the math significantly. Whether you’re building a detached unit or converting an existing garage shifts the permit requirements and structural work needed. We provide exact pricing confirmed free on the call.

About this service

The cost to build an ADU varies based on whether you are converting an existing garage or building a new detached structure from the ground up. Factors like foundation work, utility extensions, high-end finishes, and site access all influence the final total. Exact pricing confirmed free on the call.

Frequently asked in Portland

What are the options for homes with in-law suites in Portland?

What's the process for an ADU quote in Portland?

What are the steps for ADU building in Portland?

What are ADU services offered in Portland?

ADU services offered in Portland encompass the full spectrum of accessory dwelling unit projects. This includes initial consultation, site assessment, architectural design, navigating the permitting process with the city, and the complete construction of the ADU. Professionals can help with detached units, attached additions, and conversions. They ensure all work complies with Portland's building codes and zoning regulations. We facilitate your access to these services.

What is involved in accessory dwelling unit financing in Portland?

What are the requirements for an affordable accessory dwelling unit in Portland?

What does an ADU builder do in Portland?

An ADU builder in Portland is a professional who specializes in the design and construction of accessory dwelling units. They manage the entire project, from initial drawings and permits to the final build-out. This includes ensuring compliance with all local building codes and zoning ordinances. They are responsible for the quality of workmanship and the timely completion of your ADU. We help you find these experienced builders.

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

630,498residents

4,723per sq mile

8ZIP codes served

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: Alberta Arts District, Hawthorne District, Sellwood-Moreland, Laurelhurst, Mississippi Avenue — and every surrounding area.