ADULocal ADU Guide

Portland region / Oregon

Portland ADU rules
& permit guide.

Portland permits several forms of ADUs, including conversions and detached homes. Its zoning guide explains how lot type, primary dwelling size and the number of units affect your options.

Editorial review 2026-09-07 · View sources

The local detail to check first

Before you choose a design

The ordinary size cap is the smaller of 800 sq ft or 75% of the main home’s living area. A qualifying basement conversion in a primary structure at least five years old has an exception.

Portland also extends into Washington and Clackamas counties. This city guide follows Portland’s permitting authority; the initial provider grouping uses Multnomah County. Short-term rental and development-charge-waiver conditions require separate review.

Local requirements at a glance

Min/max ADU size

Generally the smaller of 800 sq ft or 75% of the main structure’s living area; an exception applies to a basement ADU in a primary structure at least five years old.

Height

Detached ADUs: generally 20 ft outside required setbacks, 15 ft within them.

Setbacks

Check placement, lot coverage and base-zone setbacks together in the city guide.

Parking

No additional on-site parking is required for an ADU.

Process

Identify the project type and applicable zoning conditions before preparing the permit submission.

Your next three steps

  1. Look up the base zone and constrained-site or historic overlays in PortlandMaps.
  2. Compare a conversion with detached construction and check size, lot coverage and access requirements.
  3. Confirm the permit package and any development-charge waiver conditions with Portland Permitting & Development.

Oregon / Local requirements

Use the rules for your location

Portland’s zoning and building requirements determine the local approval path. Review short-term rental restrictions separately, especially when using a development-charge waiver.

Read the current city guidance ↗

Questions for your first planning conversation

  • Which approval path applies to my building and ADU type?
  • Do easements, trees, slope, access or fire conditions affect placement?
  • Which utility upgrades and agency reviews should be included in my budget?
  • Are preapproved plans available, and what site work still needs review?