Salem, OR Accessory Structures: ADU Rules (2026)

007(a) sets the baseline standards that apply to every accessory dwelling unit in Salem, attached or detached. Only one ADU is allowed per lot, and it may not exceed 900 square feet or 75 percent of the main building's gross floor area, whichever limit is smaller. An ADU must sit within a lawfully built structure meeting building code; it cannot be placed in a recreational vehicle, travel trailer, similar structure, motor vehicle, or any building not intended for permanent occupancy. Ownership stays tied to the main house: an ADU cannot be split off in separate condominium ownership from the underlying lot, and an attached ADU cannot be separated in ownership from the house it is attached to.

On a townhouse lot, an ADU is allowed only if the lot is at least 2,500 square feet and no more than two townhouses are attached in a row. 007(a)(6) flatly bars using an ADU as a short-term or accessory short-term rental. In exchange for these limits, ADUs are exempt from citywide dwelling-unit density caps, from overlay-zone development and design standards, and from any requirement to build a garage. Detached ADUs carry additional standards under subsection (b): they must be located in a side or rear yard, meet the setbacks in Table 700-1, which requires a minimum 12-foot setback from a local street or 20 feet from a collector or arterial, a 3-foot interior side setback, and an interior rear setback that is waived entirely for units next to a townhouse or an adjoining ADU, drops to 1 foot next to an alley, and otherwise runs a minimum of 5 feet.

Total lot coverage from all buildings, accessory structures, and the ADU together cannot exceed 60 percent of the lot, and a detached ADU cannot rise above 25 feet in height.