The State of California amended their Accessory Dwelling Unit (ADU) handbook. As part of this, local jurisdictions are no longer allowed to limit, by ordinance, the minimum square footage of ADUs. In addition, they cannot set a maximum square footage of the ADUs.
The State also says jurisdictions cannot put restrictions on ADU percentages as they relate to the existing primary dwelling. They also cannot put limits on lot coverage or floor area ratio or open space.
So, as long as your ADU meets the minimum 800 square feet, is a maximum 16 feet in height, and is set back 4 feet from the side and back of your lot, then you are good to go so long as it’s constructed in compliance with all other local building codes.