Rocklin, CA Accessory Structures: ADU Rules (2026)

Rocklin Municipal Code Section 17.67.030 makes accessory dwelling units (ADUs) and junior accessory dwelling units (JADUs) a permitted use in all zones where residences are permitted or conditional, and allows one ADU per lot with an existing or proposed single-family residence, plus a JADU on the same lot if Section 17.67.050 is met. A JADU must sit entirely within the walls of the primary dwelling, while an ADU may be attached, built within existing walls, converted from an accessory structure, detached on the same lot, or carved from unused space in an existing multifamily building, up to twenty-five percent of that building's units.

A lot with an existing multifamily dwelling may add up to eight detached ADUs if unit counts are maintained, height stays at eighteen feet or less, and four-foot side and rear setbacks are held. Section 17.67.050(B) caps detached ADU height at sixteen feet generally, eighteen feet within a half mile of a major transit stop, and twenty-five feet if attached (or the primary dwelling's height, whichever is lower); interior livable area is capped at 1,200 square feet, with the city required to permit at least 850 square feet, or up to 1,000 square feet for a unit with more than one bedroom.

Standard setbacks apply except a four-foot minimum from rear and side lines, and none for conversions of existing structures. Section 17.67.020 requires the city to process a complete ADU or JADU application within sixty calendar days, or thirty days for a pre-approved plan, and to return an incomplete application with a written explanation within fifteen business days.