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

Placer County regulates ADUs in unincorporated areas through Placer County Code Section 17.56.200 (Accessory and junior accessory dwelling units), implementing California's state ADU law (Gov. Code Sections 66310 et seq., the chapter that replaced former Section 65852.2 effective January 2025). Every residentially zoned parcel may have one primary dwelling, one ADU and one junior ADU (JADU). A detached ADU may be up to 1,200 square feet regardless of the size of the primary structure; an attached ADU is limited to 50% of the existing primary dwelling. A JADU is capped at 500 square feet and must be created within the walls of the proposed or existing primary dwelling. There is no minimum parcel size, though adequate water and sewer or septic must be demonstrated. The required setback is four feet from side and rear lot lines, and the height limit is set by the zone district but cannot be less than 16 feet. Parking may not exceed one space per ADU, and parking is exempt where the ADU is within one-half mile of transit or part of a conversion. A building permit is always required. JADUs require owner-occupancy of either the primary dwelling or the JADU (PCC 17.56.200). Renting an accessory home for 30 days or less is prohibited. ADUs in the Lake Tahoe portion of the county are subject to additional Tahoe Regional Planning Agency (TRPA) coverage and permit rules.