Accessory Structures in Marion County, OR (2026)
4 county-level rules, plus city-specific rules for 1 city in Marion County, Oregon.
Verified from official government sources
ADU Rules
Oregon law requires Marion County and its cities to allow at least one accessory dwelling unit (ADU) for each detached single-family home in urban-growth-boundary residential zones, subject only to reasonable siting and design rules. Owner-occupancy and extra off-street parking cannot be required.
ADU Rules in Marion County, OR: State-Mandated ADUs
Few RestrictionsORS 197.312(5)(a)
A city with a population greater than 2,500 or a county with a population greater than 15,000 shall allow in areas within the urban growth boundary that are zoned for detached single-family dwellings the development of at least one accessory dwelling unit for each detached single-family dwelling, subject to reasonable local regulations relating to siting and design.
Shed & Carport Rules
A carport is a residential accessory structure in Marion County. Its peak height is nine feet at the lot line, increasing with setback to 35 feet, and it counts toward the 25 percent rear-yard accessory-coverage cap under the Rural Zoning Code.
Carport Rules in Marion County, OR: Accessory-Structure Limits
Some RestrictionsMCC 17.117.030
The maximum peak height of any residential accessory structure shall be nine feet at the lot line. Such maximum height may be increased one foot for each one foot of distance from the lot line to a maximum height of 35 feet. Roof drainage shall be accommodated within the confines of the property.
Garage Conversions
In Marion County, an attached garage converted to living space is treated as part of the dwelling and must meet the same zoning and building-code standards. A detached garage turned into a living unit is regulated as an ADU or separate dwelling.
Garage Conversions in Marion County, OR: Treated as Dwelling
Some RestrictionsMCC 17.117.070
Covered or enclosed accessory buildings which are attached to the dwelling shall be considered as a portion of the dwelling and shall observe the same requirements as the dwelling. Accessory structures shall be considered as being attached to the dwelling when any portion of the accessory structure is located within five feet of the dwelling.
Tiny Homes
Marion County has no tiny-home-specific ordinance. A permanent tiny house on a foundation is regulated as a dwelling or accessory dwelling unit under state law and county zoning; a tiny house on wheels is generally treated as a recreational vehicle.
Tiny Homes in Marion County, OR: Classified by Type
Some RestrictionsORS 197.312(5)(b)(A)
“Accessory dwelling unit” means an interior, attached or detached residential structure that is used in connection with or that is accessory to a single-family dwelling.
Accessory Structures by City in Marion County
1 cities in Marion County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
All Marion County ordinances
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