ADUs are allowed in PortlandTypes:DetachedInternal
Types:DetachedInternal
Accessory Dwelling Unit (ADU) Rules for Portland, OR
Is your property eligible for an ADU?
# of Properties
206,495
Owner-occupied
73%
Zoning districts
29
Avg Home Value
$250,736
Median Lot Size
0.11 acres
Avg Income
$109,677
Residential Types:
206,495 housing units
Single Family
77%
Other
23%
Zoning Districts:
232,842 parcels · 29 districts
R5
32%(74,760)
R7
14%(33,081)
R2.5
12%(27,907)
RM1
8%(19,729)
Other
33%(77,365)
ADU Rules
What can you build in Portland, OR?
Portland, 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
Interior / Attached ADU Size Limits
- –Maximum size of 800 sq ft
- –Maximum size of 75% of the gross living area of the primary dwelling
Detached ADU Size Limits
- –Maximum size is the lesser of 800 sq ft or 75% of the primary dwelling’s gross living area (use the larger dwelling if a duplex).
Max Units
- –Max 2 ADUs if principal is a house/attached/manufactured: R20–R2.5 (min lot size+frontage) or RM1–RM4, RX, RMP, CR, CM1–CM3, CE, CX, EX (≥1 detached). Otherwise 1 ADU.
Owner Occupancy
- –Owner occupancy is not required.
Parking
- –1 space per 2 units (including ADUs); EX has no maximum
Rental Restrictions
- –Type B accessory short-term rentals allowed only if the property does not alter the development of an existing conditional use.
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.
Multnomah County
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