Can I Build an ADU on My Property? Deschutes, Crook and Jefferson Counties, Oregon

In unincorporated Deschutes, Crook and Jefferson Counties, you can build an ADU on some rural residential lots of 2 acres or more. Crook County and part of south Deschutes County require 5 acres. Oregon’s ADU law, ORS 215.495, does not reach farm or forest zoned land, and each county sets its own rules. That is the finding of SiteFacts analysis of the three county codes as read on November 5, 2026.

An ADU is a second, smaller home on the same lot as the main house. This page covers unincorporated land only. Inside a city such as Bend, Redmond, Prineville or Madras, the city’s own code applies. This is general information, not legal advice. Confirm any number with the county before you buy or build.

How do the three counties compare?

Each column shows that county’s own numbers. The sections below name the code.

	Deschutes County	Crook County	Jefferson County
Zones	RR-10 and MUA-10 (DCC 18.116.355); UAR-10, SR 2½ and WTZ (DCC 19.92.160); confirm UAR-10 lots with Deschutes County	R-5 west of Hwy 27 and south of Hwy 370. Confirm R-10 and PBR-20 with Crook County	RR-2, RR-5, RR-10 and RR-20
Minimum lot	2 acres; 5 acres in the unsewered area of T19S to T22S, R9E to R11E	5 acres	2 acres
Size cap	900 sq ft useable floor area	900 sq ft usable floor area	900 sq ft usable floor area
Distance from house	Within 100 ft	Within 100 ft	Within 100 ft
Setback from farm or forest land	100 ft from lot lines abutting F-1, F-2 or EFU	100 ft from adjacent EFU or F-1	30 ft from EFU; 40 ft from Forest Management
Fire access	20 ft right of way plus a 12 ft driveway, asphalt or concrete or engineered for 75,000 lb; or a fire provider letter on a county form	20 ft right of way plus a 14 ft driveway with 3 ft shoulders, 48 ft curve radius, 75,000 lb; Oregon engineer’s letter before occupancy; turnout on driveways over 200 ft	Road within 150 ft of all parts of the building, at least 20 ft unobstructed width, 14 ft 6 in clearance, 75,000 lb, grade within the fire official’s limit (10%), unless the fire district approves an alternative plan
Vacation rental covenant covers	The ADU and the main house	The ADU only	The ADU and the main house
Review type	Permitted outright in RR-10 and MUA-10	Site plan review	Not stated in the sections we read. Confirm with Jefferson County

What does Oregon law allow?

Oregon lets a county allow one rural ADU. It does not require it. ORS 215.495 says a county “may allow” an owner of a lot or parcel in an area zoned for rural residential use to build one. The ORS chapter 215 text sets a floor for a county that opts in. The main conditions are:

• A lot of at least two acres, outside an urban reserve
• No part of the lot in an area of critical state concern
• A single unit dwelling already sited on the lot
• No more than 900 square feet of usable floor area, and no farther than 100 feet from the house
• Compliance with sanitation and wastewater laws
• Service by a fire protection provider with professionals trained or certified under ORS 181A.410
• No vacation occupancy of the ADU, no later division that separates it from the house, and no second ADU

Rural residential land, in the statute’s terms, is outside an urban growth boundary and zoned for residential use as a primary use. That leaves out farm and forest zones. The statute sets no number for fire access width or for setbacks from resource land, so those differ by county.

Can I build an ADU in unincorporated Deschutes County?

Yes, on some lots. Deschutes allows one ADU outright in the RR-10 and MUA-10 zones under DCC 18.116.355. The same standards apply in the UAR-10, SR 2½ and WTZ zones under DCC 19.92.160. Confirm UAR-10 lots with Deschutes County. SiteFacts analysis of both sections, as printed from the county’s code site on November 5, 2026, found these conditions:

• Lot: at least 2 acres, or 5 acres in Townships 19S to 22S, Ranges 9E to 11E, the unsewered area between Sunriver and the Klamath County line. Not in an urban reserve or the Metolius Area of Critical State Concern. An urban reserve here means a state-designated urban reserve area, which is separate from the UAR-10 zone name.
• House: one single family dwelling established onsite or applied for before the county issues any building or land use permit for the ADU.
• Setback: at least 100 feet from lot lines abutting land zoned F-1, F-2 or EFU.
• Septic: approval from a sewer authority or the Deschutes County Onsite Wastewater Division before you apply.
• Access: a continuous 20 ft right of way and a continuous 12 ft driveway, asphalt or concrete or engineered by an Oregon engineer for 75,000 lb, or written confirmation from the fire provider on a county form.
• Covenant: recorded before building permits, barring vacation occupancy of the ADU and the main house. The county describes vacation occupancy as rental for vacation only, to someone with another principal residence, for a stay of 45 days or less.
• Other: no guest house or other added dwelling on the lot, and no later land division or property line adjustment that separates house and ADU.

Ask the county whether your lot needs a lot of record verification under DCC 22.04.040(B). The ADU code lists no wildfire condition. Separately, the Oregon Building Codes Division lists Deschutes County among the places that have adopted R327 wildfire standards, a section of the Oregon Residential Specialty Code, and says to check with the local building department where the requirements apply. Ask Deschutes County whether R327 applies to your ADU.

Can I build an ADU in unincorporated Crook County?

Yes, but only in part of the county. CCC 18.88.010(10) allows one ADU in the R-5 zone west of Highway 27 and south of Highway 370, subject to the standards in CCC 18.124.140(2), which require site plan review. Ask Crook County Planning whether R-10 or PBR-20 land qualifies and whether your parcel is inside that boundary. SiteFacts analysis of Crook County Chapter 18.124, downloaded from eCode360 on November 5, 2026, found these conditions:

• Lot: at least 5 acres, outside an urban reserve.
• House: one single family dwelling that is “sited,” which Crook’s code defines as existing or approved by the planning department. Deschutes and Jefferson accept a house that has been applied for.
• Setback: 100 feet from adjacent EFU or F-1 land.
• Driveway: a 14 ft driveway with 3 ft clear shoulders each side, 13.5 ft clearance, a 48 ft minimum curve radius, built for 75,000 lb, with an all weather surface of asphalt, gravel or concrete. A licensed Oregon engineer’s letter is due before the ADU occupancy permit. Driveways over 200 ft need a 20 by 40 ft turnout.
• Evacuation plan: a staged evacuation area of at least one quarter acre, kept clear of flammable material, with written authorization from its owner.
• Covenant: bars vacation occupancy of the ADU only. Deschutes and Jefferson also bind the main house.

Can I build an ADU in unincorporated Jefferson County?

Yes, in the RR-2, RR-5, RR-10 and RR-20 zones. JCZO 17.435 allows one ADU on rural residential land outside urban growth boundaries. SiteFacts analysis of 17.435 (Ordinance O-124-25), downloaded November 5, 2026, found these conditions:

• Lot: at least 2 acres, not in an urban reserve.
• House: one single family dwelling that is “sited,” which Jefferson’s code defines as “established onsite or applied for prior to or concurrently with the issuance of any building or land use permits for an accessory dwelling unit.”
• Setback: 30 feet from EFU land and 40 feet from Forest Management land.
• Access: a road within 150 feet of all parts of the building, at least 20 feet unobstructed width, 14 ft 6 in clearance, built for 75,000 lb, with grade within the fire official’s limit (10%), unless the fire service district approves an alternative plan.
• Septic: adding the ADU to an existing system needs County Sanitarian authorization, a separate 1,000 gallon tank unless the agent approves otherwise, and an existing drainfield built after January 1, 1974, with an as-built of record. A separate system for the ADU needs a site evaluation.
• Covenant: bars vacation occupancy of the ADU and the main house.

The county code, at 17.435.5.B, still lists a requirement to meet any applicable minimum defensible space requirements of the State Fire Marshal under ORS 476.392. The 2025 edition of ORS 215.495 no longer lists a defensible space condition. Confirm with Jefferson County how the code applies to your lot. Separately, JCZO 17.426 applies fire safety standards to all new construction in unincorporated Jefferson County, including Class A or B, tile or metal roofing, emergency access to within 50 feet of all buildings, and a 30 foot primary fuel break. Confirm the current text with the county.

Can I build an ADU on farm land?

No. Oregon’s ADU law covers rural residential land, not farm or forest zones. No ADU use appears in Deschutes’ EFU, F-1 or F-2 use lists or in Crook’s EFU use table. A second dwelling on farm land goes through other paths under ORS 215.283, each with its own tests:

• A relative farm help dwelling, for a listed relative whose help the operator needs in managing the farm use.
• An accessory farm dwelling, with farm income tests.
• A temporary medical hardship dwelling, for the term of the hardship, removed within three months after it ends.

In a July 2025 case we worked, the online map showed one farm zone for a 100-plus-acre Range Land (RL) parcel in Jefferson County, and county planning confirmed another. The parcel came from a partition after 1993. Under the county’s rules as we read them in July 2025, new nonfarm parcels were allowed in the EFU A-2 zone only, so that path did not reach this parcel. The lot of record path failed because the parcel did not exist in its current form before 1985. County planning wrote in July 2025 that it appeared a dwelling would not be allowed. The paths still open were farm dwellings, for example one with a farm income test. Staff said the language might be revised, so these rules may have changed since. On farm and range land, the question can be whether any house is allowed, and the answer can turn on when and how the parcel was created, not its size. Confirm the zone and the current rules with county planning, not only the map.

Crook’s farm rules are in Chapter 18.16.

Is a guest house or bunkhouse an ADU?

Deschutes defines a guest house in DCC 18.04.030 as living quarters in a detached accessory building for temporary guests, not rented or used as a separate dwelling unit, with no kitchen. A guest house cannot sit on the same lot as a rural ADU, though an existing lawful guest house can be converted to the ADU.

Jefferson allows a lot one ADU or one habitable accessory structure, not both. Under 17.434, that structure has no cooking, one bathroom plus one fixture, and 900 square feet at most. South of the Feather Drive Bridge in Juniper Butte, habitable accessory structures are paused until the bridge can carry 75,000 lb. Whether that affects an ADU there, confirm with Jefferson County.

What about land inside an urban growth boundary?

The rural standards on this page do not apply there, because ORS 215.495 covers land outside urban growth boundaries. Crook has its own rule for county zoned land inside the Prineville boundary, under CCC 18.124.140(1): one ADU per legal house, up to 900 square feet of habitable space, through site plan review, sharing the house’s road approach. For other unincorporated land inside a growth boundary, confirm the zone and code with the county.

What should I check before I buy for an ADU?

In our experience, the driveway standard and the septic answer are the two items to price first. Check these before you make an offer:

• Septic: ask for the permit and as-built records. Deschutes wants approval before you apply. Jefferson asks for an existing drainfield built after January 1, 1974, with an as-built of record, if the ADU would share it.
• Driveway: compare the table row. Crook asks for an engineer’s letter before occupancy.
• Fire district: for a rural ADU, ORS 215.495 requires service by a provider trained or certified under ORS 181A.410.
• Wells: under ORS 215.495, the house and ADU count as one unit for exempt wells. Deschutes and Crook ask for a “willing and able to serve” letter if water comes from a source other than the house’s own well.
• Vacation rental: Deschutes and Jefferson bar it in the house too.

If you are buying or building in one of these counties, our Due Diligence page covers SiteFacts Reports, which look at zoning, access and other site questions the county label leaves open. Our permitting service covers filing the application once you are ready. Building permit package submittals: from $750. The city or county that issues the permit approves it. See our Deschutes County page, Crook County page and Jefferson County page for local detail. SiteFacts is a product of Sand & Sage Solutions LLC.

Quick answers

Can I build an ADU on less than 2 acres?

Not under the rural ADU rules we read. The state floor in ORS 215.495 is two acres, and Crook and part of south Deschutes County ask for 5. Confirm other options with the county.

Can I rent an ADU as a vacation rental?

No. ORS 215.495 says a county may not allow a rural ADU to be used for vacation occupancy. Deschutes and Jefferson extend the covenant to the main house. Crook’s covers the ADU only.

Can I build an ADU on farm land?

Not as a rural ADU. Oregon’s ADU law covers rural residential land, not farm or forest zones. A second dwelling on farm land goes through farm dwelling or hardship paths. Forest zones have their own tests. Confirm with the county.

Can I add an ADU to a lot with a guest house?

In Deschutes, no, though an existing lawful guest house can be converted to the ADU. Jefferson allows one ADU or one habitable accessory structure, not both.

This guide is general information from Sand & Sage Solutions, not legal advice. For a question about what your lot allows, confirm with the county planning department.