Doing some research for a recently project had us looking up ADU regulations in Columbia County in Oregon. I’ve shared the actual code language below to make it easier for you to find the information you need. In general, this is one of the more restrictive ADU codes we have found . It sounds like the people who wrote this code either don’t want ADUs, or are listening to NIMBYs or others who are anti-ADU.

The actual zoning language:

224 Accessory Dwelling Units

1. One accessory dwelling unit is allowed in conjunction with a detached single-family dwelling on a lot zoned for single-family development within an Urban Growth Boundary (UGB) of a city. UGB areas have the following residential zoning districts: Single-Family Residential (R-10), Single-Family & Two-Family Residential (R-7), and Rural Residential (RR-5 and RR-2).

2. An ADU shall contain a kitchen, bathroom and a living/sleeping area that is completely independent of the primary dwelling. Recreational vehicles are not allowed as an accessory dwelling unit. Creation of a new Accessory Dwelling Unit may be accomplished through any of the following methods:

   1. A. Attached to the primary dwelling by converting a single-family dwelling’s existing living area, attic, basement or garage;

   2. B. Attached to the primary dwelling by adding floor area to the existing single-family dwelling;

   3. C. Constructing a detached accessory dwelling unit on the developed site including siting of a manufactured dwelling;

   4. D. Converting an accessory building, or portion thereof, to an accessory dwelling unit; or,

   5. E. Constructing a new dwelling with an internal accessory dwelling unit and, ~ 24 ~

   6. F. Constructing a new dwelling and converting the existing dwelling to a detached ADU, provided both dwellings meet the minimum zoning requirements.

3. The County will require the proposed Accessory Dwelling Unit to comply with the Gross Habitable Floor Area, and Owner Occupancy requirements as imposed by the City for the unincorporated portion of the City’s Urban Growth Boundary Area.

4. Domestic Water:
   Documentation shall be submitted to LDS that the ADU can be served by an existing public or community water district or by a private well that has been recorded with the State of Oregon Water Resources Department. LDS shall also require a Will Serve letter from the community/city water purveyor verifying the ADU can utilize the water system.

5. Sewage Disposal:
   The County Sanitarian shall review and approve the proposed method of onsite sewage disposal for the ADU for compliance with the applicable provisions in the Oregon Administrative Rules (OAR) 340-071-0205 for existing septic systems. If the ADU will utilize community sewer, documentation shall be submitted to the County that the affected city will provide sewer service.

6. Access:
   The road access to all ADUs shall be reviewed and approved by the County Public Works Department and the affected city for consistency with the applicable provisions of the County Road Standards Ordinance and the Urban Growth Area Management Agreements between the affected city and Columbia County.

7. Siting Requirements/Standards:
   The proposed ADU must comply with the underlying zone R-10, R-7, RR-5 and/or RR-2 Zones’ minimum yard setback requirements for primary dwellings. Height limitations and lot or parcel coverage requirements shall be the same as the underlying zone.

8. On Site Parking:
   The ADU shall provide one additional on-site parking space if the primary dwelling has less than three available on-site parking spaces (inclusive of garage and driveway).

9. Location of Entrances:
   For an attached ADU only one entrance to the residence may be located on the front of the dwelling facing the street, unless the primary dwelling contained additional door entrances before its conversion to an ADU. An exception is entrances that do not have access from the ground such as entrances from balconies or decks.

10. Exterior Design and Appearance:
    ADUs shall maintain consistency with the primary dwelling. For an ADU that is created by an adding floor area to the existing primary dwelling, the ADU shall have the same siding and roofing materials and exterior paint colors as the primary dwelling. For a detached ADU the County will require compliance with clear and objective design and appearance regulations adopted by the City where the UGB is located. ~ 25 ~

11. Divisions of Property:
    The division of a property containing an ADU shall comply with the minimum and applicable provisions of Zoning District and Subdivision and Partitioning Ordinance. Establishing a new ADU shall not allow the further division of RR-5 and RR-2 properties provided for in Sections 606 and 627 of the County’s Zoning Ordinance.

12. Alteration:
    If an existing authorized detached accessory structure, or portion thereof, is converted into an ADU, it is exempt from the minimum setback standards for primary dwellings. Any floor area that is added to this structure must not increase the setback non-conformity. Proposed expansions are not eligible to be approved with a Variance to the setback standards for single-family development.

13. Existing Non-conforming ADU:
    An existing, non-conforming second dwelling on a lot or parcel in any residential zone permitted by this section may be determined to be a conforming ADU through an approval process that includes the following:

    1. A. All necessary building permits and occupancy authorization is obtained to assure the ADU complies with the applicable fire, life & safety and building codes per the Oregon Residential Specialty Code and

    2. B. The ADU complies with other requirements of this section, such as size, floor area, water, sewerage, entry and access.

Commentary:

Their decision to impose style restrictions is terrible policy. In fact, I believe style restrictions should be illegal. It has nothing to do with protecting the health, safety, or welfare of the public and has no place in codes.

Further, the requirement to create an additional parking space is another sign that they don’t actually want to make building ADUs easy. In fact, this is an overreach by dictating how you can use your private property. Parking requirements make housing more expensive, directly lead to more traffic congestion, and have nothing to do with the health, safety, or wellfare of the public. Again, these types of regulations should be outlawed on the national level.

The only positive thing I can say about these ADU regulations is they at least allow ADUs. Other than that, this is an example of how to write a terrible ADU code that makes them harder to build and more expensive.