(a) "Accessory dwelling unit" means a residential structure that is used in connection with or that is auxiliary to a single-family dwelling.

(b) "Area zoned for rural residential use" means land that is not located inside an urban growth boundary as defined in ORS 195.060 and that is subject to an acknowledged exception to a statewide land use planning goal relating to farmland or forestland and planned and zoned by the county to allow residential use as a primary use.

(c) "Historic home" means a single-family dwelling constructed between 1850 and 1945.

(d) "New" means that the dwelling being constructed did not previously exist in residential or nonresidential form. "New" does not include the acquisition, alteration, renovation or remodeling of an existing structure.

(e) "Single-family dwelling" means a residential structure designed as a residence for one family and sharing no common wall with another residence of any type.

(2) Notwithstanding any local zoning or local regulation or ordinance pertaining to the siting of accessory dwelling units in areas zoned for rural residential use, a county may allow an owner of a lot or parcel within an area zoned for rural residential use to construct a new single-family dwelling on the lot or parcel, provided:

(a) The lot or parcel is not located in an area designated as an urban reserve as defined in ORS 195.137;

(b) The lot or parcel is at least two acres in size;

(c) A historic home is sited on the lot or parcel;

(d) The owner converts the historic home to an accessory dwelling unit upon completion of the new single-family dwelling; and

(e) The accessory dwelling unit complies with all applicable laws and regulations relating to sanitation and wastewater disposal and treatment.

(3) An owner that constructs a new single-family dwelling under subsection (2) of this section may not:

(a) Subdivide, partition or otherwise divide the lot or parcel so that the new single-family dwelling is situated on a different lot or parcel from the accessory dwelling unit.

(b) Alter, renovate or remodel the accessory dwelling unit so that the square footage of the accessory dwelling unit is more than 120 percent of the historic home’s square footage at the time construction of the new single-family dwelling commenced.

(c) Rebuild the accessory dwelling unit if the structure is lost to fire.

(d) Construct an additional accessory dwelling unit on the same lot or parcel.

(4) A county may require that a new single-family dwelling constructed under this section be served by the same water supply source as the accessory dwelling unit.

(5) A county may impose additional conditions of approval for construction of a new single-family dwelling or conversion of a historic home to an accessory dwelling unit under this section. [2017 c.400 §2]