ADU (accessory dwelling unit) Rules in Deschutes County, OR (2026)

In Deschutes County, the first two questions are who has jurisdiction over your address and whether your parcel sits in a zone that allows a rural ADU (accessory dwelling unit).

If your property is inside a city such as Bend, Sisters, La Pine, or Redmond, that city’s land-use code controls the local side, not the county. The county’s checklist tells applicants in those cities to contact the city’s planning department. If your property is in unincorporated Deschutes County, the county’s rural ADU rules may apply, but only in specific zones and only when several threshold conditions are met.

When rural ADUs became allowed

Deschutes County began permitting rural ADUs in unincorporated areas on December 1, 2023. The county’s program follows Oregon’s framework under Senate Bills 391 and 644. The state statute, now ORS 215.495, lets a county allow one ADU on rural residential land, and a county may add stricter local rules.

The standards for the RR-10 and MUA-10 zones are in Deschutes County Code (DCC) 18.116.355. The section was adopted December 1, 2023 and most recently amended in August 2025. The county’s research checklist lists both DCC 18.116.355 and DCC 19.92.160 as its ADU zoning code. If your parcel is in one of the other eligible zones, ask staff which section applies.

The rules only cover certain zones and parcels, and a parcel that meets the basics can still need more site-specific work.

Where rural ADUs are allowed

Per the county’s program, rural ADUs are eligible in these zones: RR-10, MUA-10, UAR-10, SR-2 1/2, and WTZ.

ADUs are not allowed in resource zones, including Exclusive Farm Use, Forest Use (F-1 or F-2), or Open Space and Conservation zones. They are also not allowed in the unincorporated communities of Tumalo, Terrebonne, or Sunriver.

The code also excludes parcels in an urban reserve area and any parcel with land in the Metolius Area of Critical State Concern.

Two neighbors on similar-looking rural land can end up on opposite sides of eligibility because of their zoning.

The eligibility basics

The county’s rural ADU path includes several threshold items that matter early:

• The property must be at least 2 acres in size, or 5 acres if located in certain areas of South Deschutes County. The code defines the 5-acre area as the unsewered unincorporated land between Sunriver and the Klamath County border in Townships 19S through 22S, Ranges 9E through 11E. The county publishes a map of it.
• Eligible properties are limited to a single ADU onsite.
• The ADU must meet the 100-foot siting limit, with different measurements for new construction and conversions as described below.
• The ADU is limited to a maximum of 900 square feet of usable floor area. Garages, carports, decks, and covered porches are excluded from that floor-area count.
• The ADU cannot be separated from the primary dwelling through a land division or a property line adjustment.
• The primary dwelling cannot be subject to a nuisance order or pending nuisance action.
• The property must be a verified legal lot of record. Many lots already qualify through a recorded partition or subdivision. The county’s FAQ says properties with unclear creation history may need a formal lot-of-record verification first.

For the 100-foot measurement, new construction is measured from the nearest portion of the primary dwelling to the nearest portion of the ADU’s usable floor area. For a conversion, it is measured to the nearest portion of the ADU, including non-usable components such as an attached garage. For conversions, the code treats a structure as existing if it was lawfully established on or before November 1, 2023. The county’s FAQ says it cannot grant variances to these state-based standards.

How the 900 square feet is measured

The county’s FAQ explains the measurement. For a one-story ADU, useable floor area is the footprint of the whole structure minus garages, decks, or porch covers. For a two-story ADU, it is the footprint plus the first-floor stair area, minus the same exclusions. No other components are exempt.

An attached garage is allowed in addition to the ADU and does not count toward the 900 square feet. It cannot contain separate rooms or partitions that look like extra living space, and it cannot have cooking facilities. The county considers garage size case by case.

Existing guest houses and the primary dwelling

The code requires one single-family dwelling on the parcel and no guest house, temporary dwelling, or other extra dwelling. An existing lawful guest house or temporary dwelling can be converted to the ADU if it meets the other criteria. Otherwise, it must be converted to a non-living accessory building. An existing house can also become the ADU while a new primary dwelling is built. The primary dwelling counts as sited if it is established, or applied for, before any ADU building or land-use permit issues.

Water, septic, and sewer

The county’s research checklist requires the septic site evaluation before the land-use application. The code says the same thing from the other direction: before you apply, the ADU needs wastewater approval from a sewer authority or the Deschutes County Onsite Wastewater Division. Establish the wastewater approval path with staff at the outset, including any proposed sewer service. Do not treat an existing connection as proof that an ADU is approved.

The county’s FAQ says an existing septic system was most likely sized for the existing house alone. The system must be upgraded or a separate new system installed. Modifying an existing system is often complicated and may not be feasible, so a separate system may be the better option. Site evaluations typically take about four weeks, depending on weather and staff capacity. Snow cover or frozen soil can delay them in winter.

For water, the code sets different rules depending on the source:

• Onsite domestic well: the ADU must keep the well setbacks the Water Resources Department requires. The house and ADU count as one unit for exempt groundwater use. If an exempt well serves the ADU or its gardens, no part of the parcel can be in a groundwater-restricted area. Talk to the Oregon Water Resources Department about the well before design.
• Any other water source: at application, provide a letter from the supplier confirming it is “willing and able to serve” the ADU.

The county’s checklist also says to confirm with the water, electric, and gas providers that they can serve the ADU.

Wildfire access and fire protection

Deschutes County ties rural ADU eligibility to fire service. The parcel must be served by a fire protection service provider whose professionals have the training or certification described in ORS 181A.410.

The ADU also needs adequate access for that provider. The code gives two ways to show it:

1. Meet the physical standard: a continuous right-of-way at least 20 feet wide with at least 13.5 feet of vertical clearance, plus a continuous onsite driveway at least 12 feet wide with 20 feet of horizontal clearance and 13.5 feet of vertical clearance. The driveway must have an all-weather surface such as asphalt or concrete, or be designed to support 75,000 pounds gross vehicle weight as certified by an Oregon-registered professional engineer.
2. Get written confirmation from the fire protection service provider, on a county form, that access meets the district’s minimum requirements for emergency service.

The county publishes a fire district access form and ADU driveway access requirements. These are separate from the driveway permit. Access can drive site cost and feasibility, so we look at it before anyone picks a model.

The code also requires the ADU structure to be set back at least 100 feet from any lot line that borders F-1, F-2, or EFU-zoned land, in addition to the underlying zone’s setbacks. On a rural parcel next to farm or forest land, that setback and the 100-foot distance limit can leave a small buildable area.

Rental and occupancy rules

Long-term rental of an ADU is permitted. Vacation rental is not. The county prohibits using either the primary dwelling or the ADU as a vacation rental.

The county defines a vacation rental as a unit rented for vacation purposes where the occupant has another principal residence and the authorized occupancy does not exceed 45 days. Before building permits are issued, a restrictive covenant reflecting these limits must be recorded at the County Clerk’s office.

The county’s FAQ also says an ADU needs its own address for emergency services. Property taxes are handled by the Deschutes County Assessor’s Office.

The permit path

Depending on your parcel, a rural ADU project may involve several permits, including a Site Evaluation Permit, a Planning ADU Permit, an Onsite Permit, a Driveway Access Permit, and a 1 and 2 Family Dwelling or Structural Permit.

The research checklist lays out the order:

1. Preliminary checks: acreage, eligible zone, the county’s Basic Zoning Checklist, utility service, and fire district access. The site evaluation must be completed before the land-use application.
2. Contact planning staff to confirm the property can qualify. A pre-application meeting is optional but can help.
3. Apply for permits: the septic site evaluation, then the Planning ADU Permit, with the onsite installation permit at the same time if applicable. Next come a driveway permit if the property lacks one, and the building permit.

For the building permit, the county’s matrix calls for a 1 and 2 Family Dwelling permit for a new detached or attached ADU. Conversions, including garage conversions, interior units, and above-garage units, use a Structural permit. Building a new primary residence and a new ADU at the same time takes two dwelling permits.

Typical required documents include a plot plan, the deed, construction plans, and written responses to the applicable standards and criteria. The county advises homeowners to contact staff before applying.

What Wolf checks first

For a Deschutes County project, we usually want to know:

1. Is the parcel inside a city or in unincorporated county?
2. What is the zone, and is it on the eligible list (RR-10, MUA-10, UAR-10, SR-2 1/2, WTZ)?
3. Does the parcel meet the 2-acre minimum (or 5 acres in parts of South Deschutes County), and is it a verified lot of record?
4. Is there an existing primary dwelling, and can the ADU sit within 100 feet of it while staying 100 feet from any adjoining farm or forest zone?
5. Has the required site evaluation been completed before the land-use application, and are wastewater and water service confirmed?
6. Do the road and driveway meet the county’s access standard, or will the fire provider sign the access form?
7. Is there a guest house, hardship dwelling, or RV dwelling on the property that would have to be converted?

The answers decide whether the project can happen at all, so we work through them before finish selections.

Modular homes in Deschutes County

Wolf builds modular homes and ADUs to residential building code in our Battle Ground factory. They are not HUD code (the federal standard for manufactured homes) manufactured homes, even though the county’s FAQ says a manufactured home can also serve as an ADU. Building modular can simplify parts of construction, but the structure still goes through the applicable state and local review, and the property still needs local placement, foundation, utility, and inspection approvals. The BCD guide for local building departments notes that the Oregon insignia is not a certificate of occupancy.

Deschutes County, or the city with jurisdiction, still approves the site-specific pieces.

Wolf also serves Bend. Madras is in Jefferson County, so the Deschutes County rules here do not apply there.

For delivery routes, snow, and how Deschutes compares with other mountain counties, see mountain cabins and ADUs in the Cascades.

Start with the address

If you are planning an ADU in Deschutes County, send us the property address and intended use. The free property evaluation starts with jurisdiction, zoning, acreage, utilities, and model fit.

For statewide background, read our Oregon ADU rules guide. For model fit, compare the Wolf model lineup. For budgeting, see ADU costs and the Oregon ADU cost guide.

Ready to find out what your parcel can support? Get a free Wolf property evaluation and we will check your exact address against Deschutes County’s rural ADU rules.

This is general information, not legal advice. Confirm current rules, fees, and application requirements with Deschutes County or the city that has jurisdiction over your property.