ADUs are allowed in Unincorporated ColumbiaTypes:DetachedInternal
Types:DetachedInternal
Accessory Dwelling Unit (ADU) Rules for Unincorporated Columbia, OR
Is your property eligible for an ADU?
# of Properties
6,920
Owner-occupied
76%
Zoning districts
34
Median Lot Size
1.95 acres
Avg Income
$98,841
Residential Types:
6,920 housing units
Apts (4+ units)
97%
Other
2%
Zoning Districts:
16,009 parcels · 34 districts
PF-80
33%(5,286)
RR-5
33%(5,255)
FA-80
9%(1,396)
RR-2
7%(1,084)
Other
19%(2,988)
ADU Rules
What can you build in Unincorporated Columbia, OR?
Unincorporated Columbia, OR follows state and local rules for Accessory Dwelling Units. Here is a concise overview of the local rules.
Eligibility
- –Internal / Attached ADU: By Right
- –Detached ADU: By Right
Owner Occupancy
- –Owner-occupancy required per city rules for the unincorporated area.
Parking
- –1 additional on-site parking space per ADU if the primary dwelling has fewer than 3 on-site spaces (garage and driveway included); no maximum; applies within Urban Growth Boundaries in zones R-10, R-7, RR-5, RR-2.
ADU State Law
What can you build in Oregon?
- –In urban growth areas, Oregon law requires cities and counties to allow at least one ADU on lots zoned for detached single-family homes.
- –Local jurisdictions cannot require owner occupancy for ADUs, but may regulate short-term or vacation rentals.
- –There are no statewide limits on ADU size, height, setbacks, lot size, or floor area ratio. Local zoning rules apply.
- –Parking requirements, if any, are set by the local jurisdiction, subject to state limitations.
- –Some cities may allow more than one ADU per lot, depending on local code.
- –Oregon law does not require counties to allow ADUs in rural residential zones. Whether an ADU is allowed depends on county zoning.
- –ADUs in rural residential areas cannot be used for short-term or vacation rentals.
- –Additional requirements may apply related to wildfire risk, water supply, septic capacity, and fire access.
- –Counties may impose additional restrictions beyond state law or choose not to allow ADUs at all.
- –If a county allows ADUs, state law imposes strict limits, including a minimum 2-acre lot size, a maximum ADU size of 900 sq ft, a location within 100 ft of the primary dwelling, and a limit of one ADU per parcel.
What's allowed on your lot?
These are the municipality-wide rules. What's allowed on a specific property also depends on state laws, setbacks, floor area ratio, lot coverage, environmental constraints, topography, and other property-specific factors. Search your address on FutureLot to see what's allowed on your property.
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ADU rules in other Oregon municipalities
Rules change at the town line. Check the municipality your property is actually in.
Columbia County