Benton County, OR Accessory Structures: Shed & Carport Rules (2026)

405(5), part of the Rural Residential zone's siting standards, carves out reduced setbacks for accessory buildings and other non-residential structures, covering most backyard sheds, detached garages and workshops. A non-residential structure still cannot be built within the setback abutting a road, but no setback at all is required for one of 120 square feet or less, roughly a 10-by-12 shed. A larger structure can still use a reduced 3-foot side or rear setback, instead of the zone's standard 8-foot side and 25-foot rear setbacks, if it meets three conditions together: it is detached from other buildings by 5 feet or more, it does not exceed 20 feet in height, and it does not exceed 500 square feet in area.

405(5)), so the 120-square-foot no-setback line and the 500-square-foot, 20-foot, 3-foot-setback combination apply broadly across the county's residential Development Code zones. A shed that exceeds 500 square feet, or that sits closer than 3 feet to a property line, falls back to the zone's ordinary side and rear setbacks and, depending on size, may need a building permit under the Benton County Building Code (BCC Chapter 11) and its adopted Oregon specialty codes. This standard applies in unincorporated Benton County; Corvallis and Philomath issue accessory structure permits under their own municipal codes within city limits.