Calaveras County, CA Accessory Structures: ADU Rules (2026)

040 of the Calaveras County Code governs every accessory dwelling unit (ADU) built in the unincorporated county, which is nearly the whole jurisdiction outside Angels Camp. An ADU does not count against the lot's allowable density, and the parcel must already carry, or be building, a primary single-unit or multi-unit dwelling before a building permit for the ADU is accepted. Lots with an existing single-unit dwelling may add one detached ADU or one unit built within the existing house, plus a junior accessory dwelling unit (JADU) of up to 500 square feet carved out of the house or an attached garage.

Lots with existing multi-unit buildings may add two detached ADUs, or convert up to twenty-five percent of the units in a multi-unit structure into ADUs. Attached and detached ADUs are capped at 1,200 square feet of floor area. Interior side and rear setbacks fall to a minimum of four feet, and an ADU built above a garage needs no more than a five-foot setback from interior lot lines. An ADU built inside an existing structure can add up to 150 square feet just for a dedicated entrance.

090(B) of the county code, before the ADU can be approved. No fire sprinklers are required for the ADU if the primary residence does not need them. 2 allows, and short-term or transient occupancy under thirty days is prohibited outright. The county's Planning Department must approve or deny a complete, code-compliant application ministerially, with no discretionary hearing, and no automobile parking is required for the unit itself.