Oregon ADU Rules — Statewide Basics

Oregon law requires most cities to allow at least one ADU per single‑family house within urban growth boundaries. Cities can use reasonable siting/design rules, but cannot mandate owner‑occupancy or extra off‑street parking (with limited exceptions).

See Portland Rules Permit Steps Find Builders
Modern detached ADU behind an Oregon home
TL;DR: Oregon requires ADUs in most cities (within UGBs). Cities can set clear, objective siting/design rules—but not owner‑occupancy or extra parking requirements. Check your city page for size, height, and setback numbers.

At‑a‑Glance: Statewide Rules

Must allow ADUs
Cities ≥2,500 pop. & counties ≥15,000 within UGB must allow at least one ADU per house.
DLCD guidance
Owner‑occupancy
Local codes may not require owner occupancy (except limited vacation rental contexts).
HB 2001 update
Off‑street parking
Local codes may not require extra off‑street parking for ADUs (limited exceptions).
DLCD guidance
Max size
Set locally. Many cities use ~800–900 sf or 75–85% of the house. {{verify locally}}
Height & setbacks
Usually same as other accessory buildings. {{verify locally}}
Building code
Permitted under the Oregon Residential Specialty Code (ORSC).
ORSC

Tip: City pages have the exact numbers. Start with Portland, then check your city’s planning portal.

Typical Size & Height (Illustrative)

Many cities use maximum ADU size of 800–900 square feet or 75–85% of the primary dwelling. Heights often align with accessory buildings. Verify locally. Max size (sf) 800–900 (typical) Percent of house 75–85% (typical) Height Accessory‑building rules

These are common patterns—not statewide mandates. Always confirm your city’s code. {{verify locally}}

Permit Steps (ORSC)

1) Confirm Zoning

Call or check your city planning portal to confirm ADU allowance on your lot (UGB, zone, overlays) and get the exact size/height/setbacks.

2) Choose ADU Type

Detached, attached, interior conversion, or garage conversion. Sketch a basic site plan with utility routes.

3) Plans & Submittal

Prepare drawings that meet the Oregon Residential Specialty Code (ORSC). Include structural, energy, and life‑safety details.

4) Apply for Permits

Submit to your building department. Pay plan review and permit fees; some cities assess or waive/reduce SDCs for ADUs.

5) Build & Inspect

Follow inspection milestones (foundation, framing, mechanical, plumbing, electrical). Coordinate utility connections or sub‑metering.

6) Final & Occupy

Obtain final inspection/CO. Check any local rules for rentals (long‑term vs short‑term) and parking/driveway use.

Resources: DLCD ADU Guidance • ORSC (Building Codes Division)

Oregon ADU FAQ

Can my city require me to live on the property?
No. State law bars local owner‑occupancy mandates for ADUs (limited exceptions for vacation rentals). See DLCD guidance linked above.
Do I have to add off‑street parking?
No, cities generally may not require additional off‑street parking for ADUs (limited exceptions). Check your city page for any nuanced cases.
Are there statewide size or height limits?
No. These are set locally. Many cities use maximums around 800–900 sf or 75–85% of the primary dwelling, and apply accessory‑building height/setbacks. {{verify locally}}
Can I build two ADUs on one lot?
Some cities allow two (e.g., one detached plus one interior/attached), consistent with state guidance encouraging more housing. Check your city’s code.
Do I need separate water/sewer meters?
Not always. Separate connections can add cost; some cities allow shared connections. Confirm with your utility and building department.
Are ADUs required everywhere in Oregon?
Mandate applies within urban growth boundaries for cities ≥2,500 and counties ≥15,000 population. Rural areas outside UGBs may differ.

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