ADUs and RVs as options for secondary dwellings

Second dwelling options: Accessory Dwelling Units (ADUs) in rural residential areas and Recreational Vehicles (RVs) in rural and urban residential areas

To help support access to more affordable housing in unincorporated Clackamas County, on May 8, 2024, the Board of County Commissioners approved amendments to the county’s Zoning & Development Ordinance (ZDO) that will allow for county residents to:

1. Construct an accessory dwelling unit (ADU) on certain properties in rural residential areas, and
2. Use a recreational vehicle (RV) as a second dwelling on certain urban and rural residential properties.

These rules are not yet in effect. The formal adoption of these rules is expected to occur at the Board’s business meeting on June 6, and, if adopted, they will go into effect later in the summer.

See video below for an overview of the proposed rules as presented to the Planning Commission in February 2024.

Meetings and public hearings

Requirements for rural ADUs

An accessory dwelling unit is a second (usually smaller) dwelling unit located on the same lot as a detached single-family home or manufactured home. It may be attached or detached from the single-family home or manufactured home.

Historically, state law has not allowed ADUs in rural areas. State legislation in 2021 and 2023 changed these rules, however, and now counties can allow ADUs in certain areas zoned for rural residential use, as long as the site is both outside of an urban growth boundary (UGB) and outside of an urban reserve.

Construction of ADUs in these areas will have to meet the standards described below.

Property requirements:

• Be at least two acres in size;
• Have only one single-family dwelling (could be a manufactured dwelling); 
• Not be subject to an order or pending action declaring it as a nuisance property;
• Be served by a fire protection service provider, and
• Cannot be subdivided to separate the primary dwelling and the ADU.

ADU requirements:

• No larger than 900 square feet;
• Located within 100 feet of the single-family dwelling;
• Comply with all applicable state laws relating to water supply, sanitation and wastewater disposal;
• Comply with all applicable state laws relating to wildfire mitigation standards, including:
  • Fire hardening of structures
  • Defensible space surrounding structures
  • Adequate access for emergency services, firefighting equipment, safe evacuation
• Would not have access to public sewer, and would need to connect to an existing or new septic system; 
• In some cases, would not have access to public water and would need to rely on a well, and
• Could not be used as a short-term rental.

Once the new rules are in effect, construction of ADUs may be permitted in the areas identified in blue on the map below.

Requirements for RVs

A recreational vehicle is a vehicle licensed by the state that:

• Is designed for human occupancy
• Is designed to be used temporarily for recreational, seasonal, or emergency purposes, and
• Has a gross floor area not exceeding 400 square feet when set up. 

RVs include park trailers, travel trailers, pick up campers, motor homes, fifth-wheel trailers, and camping and tent trailers.

Historically, state law has not allowed using an RV as a residence on private property except in limited circumstances, such as temporary dwellings for care or while building a permanent dwelling. However, based on state legislation in 2023, SB 1013, counties now may allow property owners to place one RV on certain property to use as a second dwelling.

Once the new ordinance is in effect, RVs may be permitted as second dwellings on land zoned for residential use, as shown on the following map, that is:

1. Inside the Portland Metro UGB (shown in orange) or
2. Both outside of an urban growth boundary (UGB) and outside of an urban reserve (shown in blue).

Property requirements

• Only one RV may be sited as a second dwelling on a property
• The primary dwelling (which may be a manufactured dwelling) must be the only other dwelling on the property, and: 
• Must be owner-occupied
• No part of dwelling is rented
• The property may not contain a guest house

RV requirements

While RVs are not subject to building codes, as second dwelling on properties described above they must meet the following requirements:

• Subject to rental agreement between the owner of the primary single-family dwelling and the occupant of the RV
• Property owner must provide “essential services” to RV space - water, sewage disposal, electrical supply, and, if required by state law, any drainage system 
• RV cannot be used as a short-term rental
• Minimum distance of RV from primary dwelling – 10 feet
• Maximum distance of RV from primary dwelling – 100 feet
• RV must meet same property line setbacks as primary dwelling
• Must contain working toilet and sink