Accessory dwelling unit construction cost

Looking for accessory dwelling unit construction cost in Portland, OR? Call AccessoryDwellingUnit Pros 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 custom project, so costs vary based on your specific choices. Site conditions are the biggest factor; if your land requires significant grading, utility extensions, or foundation work, those expenses add up quickly. Choosing high-end finishes, custom cabinetry, or complex roof lines will also push the budget higher compared to a standard design. Prefabricated units often offer predictable costs, while custom site-built structures allow for more flexibility but can be harder to estimate upfront. Exact pricing confirmed free on the call.

About this service

Building costs vary based on the size of the unit, the quality of finishes, the complexity of the site foundation, and utility connections. You should consider these expenses when budgeting for a long-term property investment or home expansion. Exact pricing confirmed free on the call.

Frequently asked in Portland

What are the disadvantages of ADUs in Portland?

In Portland, disadvantages can include navigating specific neighborhood design guidelines and ensuring sufficient utility connections for the new unit. Permitting can also take time, particularly for complex projects. Discussing these potential challenges with local ADU professionals is advisable.

How much does an ADU cost in Oregon?

The cost of an ADU in Oregon, including Portland, depends on factors like size, foundation type, materials used, and any necessary site preparation. Attached ADUs are often less expensive than detached ones. For an accurate cost, a professional assessment is needed to provide a detailed quote.

What are the rules for ADUs in Oregon?

Oregon has state laws that promote ADUs, and Portland has specific zoning ordinances that govern their development. These rules typically cover lot coverage, setbacks, height limits, and parking requirements. Engaging with pros familiar with Portland's ADU regulations is essential for a smooth process.

Is an ADU allowed in Maryland?

Yes, ADUs are permitted in Maryland, with local regulations varying by jurisdiction. Maryland has been expanding ADU allowances to address housing shortages. If you need ADU services in Maryland, connect with local Maryland ADU experts.

This particular grant is not applicable in Oregon. When you call for a quote, ask about any available local or state incentives for ADUs in the Portland area.

What are the rules for ADUs in California?

California's ADU laws are generally very permissive, aiming to simplify construction and increase housing stock. Many cities have streamlined permitting and reduced parking requirements. For projects in California, consulting with California-based ADU specialists is recommended.

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: Pearl District, Hawthorne, Alberta Arts District, Sellwood-Moreland, West Hills, Downtown Portland — and every surrounding area.