Petaluma, CA Accessory Structures: ADU Rules (2026)

030 lets an accessory dwelling unit be created within any residential or mixed-use zoning district, including planned unit developments, under subsection A. 1; a homeowner may add both an ADU and a junior ADU together only if one of the two sits within the existing or proposed single-family home or an existing accessory structure, any addition beyond the existing footprint is 150 square feet or less and limited to ingress and egress, and the unit has exterior access and complies with fire setbacks. 2. Living area is capped at 1,000 square feet, or 50 percent of the primary home's living area if attached, unless the unit is 800 square feet or smaller with a 16-foot height limit and four-foot side and rear setbacks, in which case lot coverage, floor area ratio, and open-space limits do not apply at all under subsection J.

Standard setbacks are four feet from the side and rear lot lines under subsection G, with no setback required for in-kind reconstruction of an existing noncomplying structure. No additional parking is required for a new ADU under subsection H. Any ADU permitted after September 7, 2017, must be rented for terms longer than 30 days and can never be used as a short-term vacation rental under subsection P. 2) set a statewide floor for ADU approvals, any Petaluma requirement here that is more restrictive than current state law does not control.