ADU laws in Oregon

In plain words

Oregon was one of the first states to require cities to allow ADUs. An ADU (accessory dwelling unit) is a second, smaller home on the same lot as a house. It can be inside the house, attached to it, or a separate backyard cottage. Since 2018, cities with more than 2,500 people must allow at least one ADU with each detached house. Counties with more than 15,000 people must do the same. The rule applies inside an urban growth boundary, the line drawn around a city where urban building is planned. Cities can still set reasonable rules about where an ADU sits and how it looks. Since 2020, they cannot make you live on the property, and they cannot make you add a parking space. One exception: they can add those rules if the ADU is a vacation rental. Rural land works differently. A county may choose to allow one small rural ADU, up to 900 square feet, on a lot of at least 2 acres. Not every county has opted in, so ask yours. A deed restriction is a rule written into a property's deed. An HOA (homeowners association) also sets rules for its neighborhood. Deed rules signed since 2021 and HOA rules adopted since 2020 already cannot ban ADUs. Starting January 1, 2027, older ones lose that power too. For deeds, this applies only inside urban growth boundaries. Size limits, height limits and fees still differ by city. Portland, for example, caps most ADUs at 800 square feet and waives some fees if you agree not to run a short-term rental. You still need permits, and your lot may have limits of its own. Check your city's code before you design anything.

The rules at a glance

What to do next

1. Confirm whether your property is inside a city over 2,500 people or a county's urban growth boundary; your city or county planning counter can tell you your zone.
2. Read your city's ADU code for size, height, setback and design limits, and ask for its pre-approved ADU plans if it has them (Bend and Eugene do).
3. Ask about system development charges and any waiver before you budget; in Portland the waiver comes with a 10-year no-short-term-rental covenant.
4. If you are on rural land, ask the county whether it has adopted rural ADU rules under ORS 215.495; if not, a rural ADU is not allowed.
5. If your HOA rules or deed ban ADUs, note that state law voids most such provisions starting January 1, 2027 (deed restrictions only inside urban growth boundaries); talk to a real estate attorney about your documents and timing.
6. If a city refuses or stalls an application you believe meets state law, you can contact the state Housing Accountability and Production Office.

Grants, loans and tax breaks

• ADU community pilot program (HB 3335, 2021): The state housing agency granted money to a nonprofit to help homeowners at or below area median income build ADUs and rent them to lower-income tenants for at least 10 years. This was a one-time pilot; whether it still takes applications is unconfirmed. Program page

What your town still decides

Cities write their own ADU code within the state floor, so size caps, height, setbacks and fees still vary city to city. Since 2019, covered cities cannot demand owner occupancy or extra parking. A state office, the Housing Accountability and Production Office (run by DLCD and the Building Codes Division), answers questions and takes complaints about cities that do not follow state housing laws. Outside urban growth boundaries, ADUs depend entirely on whether the county has opted in to rural ADUs.

Examples of local rules

• Portland: One ADU with a house in most residential zones, two on some larger lots that meet frontage and lot-size conditions. Size cap is 75% of the house's living area or 800 sq ft, whichever is smaller (basement units in houses at least five years old are exempt). No extra parking. The city waives system development charges if the owner signs a 10-year covenant not to use the property as a short-term rental. Source
• Bend: Up to two ADUs per lot, each up to 800 sq ft. No minimum on-site parking. Detached ADUs need 6 ft of separation from the house. System development charges apply. The city offers a pre-approved plans program. Source
• Eugene: Runs a pre-approved ADU plans program: twelve designs sold for $500 each plus one free city design. Using a pre-approved plan skips plan review fees; the owner still needs a site plan and permit. Source

What we’re still confirming

• Whether the 2021 state ADU pilot (a grant run through Hacienda CDC) still accepts homeowners isn't confirmed.
• State law doesn't require cities to approve ADUs without a hearing; ask your city whether a building permit alone is enough.

Laws, bills and citations

This is general information, not legal advice. Your town, village, city or county decides what can be built on your property. If something here looks out of date, email the team.