The District’s Code of Regulations (Section 5.32.020A) states that Accessory dwelling units as defined in California Government Code § 65852.2(j)(1) (also referred to as in-law, residential secondary, or efficiency units) which will not require a separate connection to the water system, and which are either built outside the existing space of a single-family residence or accessory structure or are built in conjunction with a new single-family residence, are subject to the fees and charges specified in Section 5.08.040, which includes a Facility Reserve Charge that is proportionate to the additional burden these units place on the water system, and Section 5.56.060.
As used herein, “existing space” means the area within and including the original walls and roofline of the permitted single-family primary residence or permitted accessory structure.
District Title 5 Regulations (PDF)