Medford, OR Accessory Structures: ADU Rules (2026)

821 defines an ADU as either attached (sharing a wall or stacked above/below the primary home) or detached, and specifies that a single-family home with an ADU is never reclassified as a duplex or multi-family dwelling. Exactly one ADU is allowed per primary dwelling, and the primary dwelling must be a detached single-family home, an attached single-family home divided by a lot line such as a duplex or townhouse, or a manufactured home on an individual lot. The maximum gross floor area of the ADU is capped at 75 percent of the primary dwelling's floor area or 900 square feet, whichever is less; converting interior space of the primary home into an attached ADU is separately capped at 50 percent of the primary home's floor area or 900 square feet.

ADUs must meet the same lot coverage and setback standards that apply to the primary dwelling, but the property gets a 10 percent lot-coverage bonus reserved exclusively for the ADU. No additional off-street parking is required for the ADU itself, and where the existing primary dwelling doesn't meet the parking table, the required parking can be reduced by up to one space if the parcel sits in the Central Business overlay or a Transit Oriented District, within a quarter mile of a transit stop, within a half mile of a bike lane or multi-use path, has 24 feet of frontage with on-street parking, or the structure predates January 1, 2019.

Where an alley provides access, the ADU must take vehicle access from the alley unless off-street parking isn't required. 186 to become a legal nonconforming structure, provided all building, fire and life-safety codes are ultimately met.