ADU rules in Deschutes County

One detached ADU is permitted outright, but only in five rural residential zones and only above a hard acreage floor. DCC 18.116.355(B) allows one ADU on a lot or parcel zoned RR-10 or MUA-10, and DCC 19.92.160(B) does the same in the UAR-10, SR-2 1/2 and WTZ zones governed by Title 19. The lot must be at least two acres, or at least five acres in the unsewered South Deschutes County area between Sunriver and the Klamath County border. ADUs are not available in Exclusive Farm Use, Forest (F-1, F-2) or Open Space and Conservation zones, nor in the unincorporated communities of Tumalo, Terrebonne or Sunriver. The county opted into the state's rural ADU authorization (SB 391, ORS 215.495) with Ord. 2023-014, and applications opened December 1, 2023.

Attached and internal ADUs clear the same zone and acreage gates as detached ones; the code does not distinguish by form. DCC 18.116.355(A)(1) defines an ADU simply as a residential structure used in connection with or auxiliary to a single-family dwelling, and the 100-foot separation standard in (B)(8) is satisfied trivially by an attached or interior unit. The county's ADU Research Checklist publishes a building permit matrix covering six ADU types: Detached, Attached, Interior (Upper Level), Interior (Lower Level), Above Garage and Garage Conversion. New construction is listed for detached and attached units (1 & 2 Family Dwelling permit); interior, above-garage and garage-conversion ADUs appear only in the conversion column (Structural permit). Read the definitional wrinkle before drawing plans: DCC 18.116.355(A)(4) defines the primary single-family dwelling as sharing no common wall with another residence of any type, yet the county's own permit matrix treats attached ADUs as permitted, so confirm an attached design with planning staff.

DCC 18.116.355(B)(7) caps the ADU at 900 square feet of useable floor area, and (A)(5) excludes garages, carports, decks and porch covers from that measurement. The county measures a one-story unit as the whole structure footprint minus those exempt components, and a two-story unit as the footprint plus the first-floor stair area. An attached garage may be added on top of the 900 square feet with no separate size cap, but it may not contain cooking facilities or partitioned rooms that read as living space. Height is set by the underlying zone, 30 feet in RR-10 under DCC 18.60.060(B), and the unit must sit within 100 feet of the primary dwelling. The county cannot grant variances to the 900-square-foot or siting standards because they come from state statute. The separate historic-home path in DCC 18.116.350 is capped instead at 120 percent of the historic home's square footage.

No owner-occupancy condition appears anywhere in DCC 18.116.355 or DCC 19.92.160, and the county's ADU planning application (rev. 8/25) walks an applicant through 17 supplemental zoning requirements without ever asking where the owner lives. The state authorization for rural ADUs, ORS 215.495, never contained one either, and for the county's Title 19 land inside the Bend urban growth boundary ORS 197A.425(1)(b)(B) affirmatively forbids owner-occupancy requirements as a condition of ADU approval. The only recorded restriction on the property is the covenant barring vacation occupancy, which binds the use rather than the owner's address, so both dwellings may be rented long term to unrelated tenants.

Neither DCC 18.116.355 nor DCC 19.92.160 imposes an off-street parking standard on ADUs, and the county's ADU planning application asks no parking question (the plot plan simply has to show existing parking along with structures and landscaping). The general parking chapter, DCC 18.116.030(D)(1), lists only Single-Unit Dwelling, Duplex and Three-Unit Dwelling at 2 spaces per dwelling unit and never names accessory dwelling units, so no ADU-specific count is spelled out; on the two-acre-and-up rural lots where ADUs are allowed, ordinary driveway parking satisfies it in practice. Inside the Bend urban growth boundary, ORS 197A.425(1)(b)(B) independently bars requiring additional off-street parking for an ADU. What the county does police is vehicle access for firefighting: DCC 18.116.355(B)(11) requires a continuous 20-foot right-of-way and a 12-foot all-weather onsite driveway, or a signed fire district form confirming adequate access.

A residential accessory dwelling unit subject to DCC 18.116.355 is a use permitted outright in the RR-10 zone (DCC 18.60.020) and the MUA-10 zone (DCC 18.32.020), and DCC 18.116.355(B) states that one ADU 'is permitted outright' where the listed standards are met. Review is administrative against clear standards, with no public hearing and no discretionary criteria. It is still a multi-permit sequence in practice: an approved septic site evaluation must exist before the land use application is filed, then the Planning ADU permit, then an onsite wastewater installation permit, a driveway access permit if the property lacks one, and finally a building permit (1 & 2 Family Dwelling for a new detached or attached unit, Structural for conversions). Properties must also be verified as legal lots of record, and combining zones such as Landscape Management or Wildlife Area can add a separate land use review on top.

The county states plainly that an ADU may be used as a long-term rental. But DCC 18.116.355(B)(18) requires the owner, before building permits issue, to sign and record with the County Clerk a restrictive covenant stating that neither the ADU nor the primary dwelling may be used for vacation occupancy. Vacation occupancy is defined in DCC 18.116.355(A)(6), consistent with ORS 90.100, as renting to an occupant who rents for vacation purposes only, keeps a principal residence elsewhere, and stays no more than 45 days. Adding an ADU therefore permanently retires short-term rental use of the whole property, which otherwise requires a county Certificate of Authority and 8 percent transient lodging tax under DCC Chapter 4.08. The ADU also cannot be sold off: DCC 18.116.355(B)(13) makes the lot ineligible for any subdivision, partition or property line adjustment that would place the ADU and the primary dwelling on different lots, and for any additional dwelling unit, guest house or temporary hardship dwelling.