Who issues the permit in Unincorporated Multnomah County?

The local building department for Unincorporated Multnomah County handles permitting. This page lists its contact details and online portal. Your mailing city is not always the permitting authority, so confirm the jurisdiction before you apply.

How do I find out the exact requirements for my project?

Run the free PermitRoadmap check for your specific project and answers. It returns the likely permits, documents, inspections, and next steps, each linked to its official source.

Do I need a permit for accessory dwelling unit (adu) in Unincorporated Multnomah County?

Permit required

Yes. In Oregon, accessory dwelling unit (adu) generally requires a permit, and Unincorporated Multnomah County is no exception.

Oregon cities over 2,500 people and counties over 15,000 must allow at least one accessory dwelling unit for each detached single-unit dwelling in areas inside the urban growth boundary zoned for detached single-unit dwellings, subject to reasonable siting and design rules; they may not require owner occupancy or extra off-street parking (ORS 197A.425, formerly ORS 197.312). Under Oregon's middle housing law (ORS 197A.420, formerly ORS 197.758), larger cities and Metro-area cities must allow duplexes through cottage clusters on residential lots, and cities of 2,500 to 25,000 outside Metro must allow duplexes. These laws change zoning only; an ADU is a new dwelling and always needs a building permit plus electrical, plumbing, and mechanical permits (ORSC R105.1 and R105.1.1).

Get the checklist for your accessory dwelling unit (adu) in Unincorporated Multnomah County. A free check first, then a free printable Permit Prep Pack.

Local detail for Unincorporated Multnomah County: Multnomah County handles zoning only. Building permits for unincorporated areas are issued under agreement by the City of Gresham (most of unincorporated east Multnomah County), the City of Portland, or the City of Troutdale, depending on the address. The office listed is Gresham Permit Services; confirm which city serves your address.

Documents you may need

Local land-use or zoning approval for the ADULikely required
Building permit applicationRequired
Site plan with setbacks, utilities, and accessRequired
Construction drawings and ORSC Chapter 11 energy complianceRequired
Separate electrical, plumbing, and mechanical permitsRequired

Possible inspections

Footing and foundation inspection
Framing and rough-in electrical, plumbing, and mechanical inspections
Insulation inspection
Final inspection before occupancy

Frequently asked questions

Do I need a permit for accessory dwelling unit (adu) in Unincorporated Multnomah County?: Yes. In Oregon, accessory dwelling unit (adu) generally requires a permit, and Unincorporated Multnomah County is no exception. The documents and inspections sections on this page list what the building department typically asks for.
Who issues the permit in Unincorporated Multnomah County?: The local building department for Unincorporated Multnomah County handles permitting. This page lists its contact details and online portal. Your mailing city is not always the permitting authority, so confirm the jurisdiction before you apply.
How do I find out the exact requirements for my project?: Run the free PermitRoadmap check for your specific project and answers. It returns the likely permits, documents, inspections, and next steps, each linked to its official source.

PermitRoadmap is an independent informational service and is not affiliated with any city, county, state agency, or permitting authority. Results are informational and do not replace confirming requirements with the local permitting authority.