Adu cost — Portland, OR | AccessoryDwellingUnit Services

Looking for adu cost in Portland, OR? Call AccessoryDwellingUnit Services 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 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

The final cost of your ADU is influenced by factors like utility trenching, site excavation, and the complexity of the architectural design. Larger units or those requiring extensive foundation work will naturally cost more than simple interior conversions or small studios. We help you prioritize your budget items to get the most value out of your square footage. Exact pricing confirmed free on the call.

Frequently asked in Portland

What are the disadvantages of ADUs?

Adding an ADU involves navigating Portland's complex permit process and meeting strict design standards. You might face limitations on parking or unit size depending on your specific zoning district. Managing a secondary rental space requires ongoing maintenance and landlord responsibilities. Consult with a professional to weigh these considerations against the potential benefits for your property value and long-term utility in Portland.

How much does an ADU cost in Massachusetts?

What are the rules for ADUs in California?

California regulations do not govern the construction of ADUs in Portland. You must adhere to the city of Portland's specific zoning codes and residential infill project rules. These local laws dictate everything from maximum unit size to setbacks. Always check with a local specialist to ensure your project complies with current Portland municipal requirements rather than out-of-state legislation.

Is ADU allowed in Maryland?

Maryland state rules do not apply to your property located in Portland. You are subject to Oregon state building codes and local city ordinances regarding secondary dwellings. Building an ADU in Portland requires following city-specific guidelines for safety and land use. Reach out to us today to get expert advice on the requirements for your specific site and project.

What are the rules for ADU in California?

The rules for California ADUs do not apply to your home in Portland. Our city has its own unique set of regulations regarding secondary units and accessory structures. It is important to focus on Portland-specific codes to ensure your project moves forward without legal issues. Call us to speak with a professional who knows the local Portland building landscape inside out.

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: Hawthorne, Alberta, Pearl District, Sellwood, Nob Hill, St. Johns — and every surrounding area.