Prefabricated accessory dwelling unit — Portland, OR

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

A prefab ADU is built in a factory and then transported to your property for final assembly. These units are often faster to build than traditional construction because the work happens in a controlled environment. If you want to minimize noise and debris on your property or need a quicker turnaround for your backyard space, this is a great option.

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: Laurelhurst, Sellwood-Moreland, Alberta Arts District, Downtown Portland, Pearl District, Vancouver — and every surrounding area.