ADUs are allowed in Forest GroveTypes:DetachedInternal
Types:DetachedInternal
Accessory Dwelling Unit (ADU) Rules for Forest Grove, OR
Is your property eligible for an ADU?
# of Properties
7,113
Owner-occupied
78%
Zoning districts
18
Avg Home Value
$514,568
Median Lot Size
0.16 acres
Avg Income
$109,331
Residential Types:
7,113 housing units
Apts (4+ units)
1%
Other
99%
Zoning Districts:
7,793 parcels · 18 districts
R-7
37%(2,850)
RMH
18%(1,397)
R-5
12%(964)
R-10
11%(873)
Other
22%(1,709)
ADU Rules
What can you build in Forest Grove, OR?
Forest Grove, 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 720 sq ft
Detached ADU Size Limits
- –Maximum detached ADU size of 720 sq ft (gross floor area)
Max Units
- –1 ADU per single-unit detached dwelling
Parking
- –0 spaces/ADU; no max; applies citywide (Zones A & B)
Rental Restrictions
- –Short-term/vacation rentals prohibited; tenancy must be longer than one month.
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.
Washington County