Cost to build accessory dwelling unit

Looking for cost to build accessory dwelling unit 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

Building an ADU involves costs for permits, site prep, foundation, framing, plumbing, and electrical work. Prices fluctuate based on whether you choose a custom design or a pre-planned layout, as well as the complexity of connecting to existing city utilities. Exact pricing confirmed free on the call.

Frequently asked in Portland

What's the process for hiring an accessory dwelling unit contractor in Portland?

What do 'accessory dwelling units ADUs' mean for Portland homeowners?

For Portland homeowners, accessory dwelling units (ADUs) represent a way to add independent living spaces to their properties. These can be detached backyard cottages, garage conversions, or basement apartments. ADUs are a practical solution for accommodating family, housing guests, or generating rental income within the city's neighborhoods. They increase property utility.

What are the steps for an emergency ADU in Portland?

An 'emergency ADU' isn't a standard term, but if you need a rapid solution for housing, the pros can expedite the process as much as possible. This might involve pre-designed ADU plans or specific construction methods. They will assess your situation and discuss the fastest, most compliant way to add living space. The focus is on efficiency and meeting urgent needs.

What is the typical accessory dwelling unit construction cost in Portland?

The typical accessory dwelling unit construction cost in Portland varies based on size, design complexity, and site conditions. Factors like foundation type, materials, and finishes play a significant role. While we don't provide exact figures here, the pros can offer a detailed breakdown during your consultation. They help you understand what influences the final price.

What permits are needed for ADU construction in Portland?

Can you recommend an ADU company in Portland?

Where can I find ADU services near me in Portland?

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

All cities in Oregon →

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, Sellwood-Moreland, Pearl District, Hawthorne District, Laurelhurst, Mississippi Avenue — and every surrounding area.