Laguna Niguel, CA Accessory Structures: ADU Impact Fees (2026)

Section 9-1-35.26(h)(1) exempts a junior accessory dwelling unit, and any accessory dwelling unit with less than 750 square feet of interior livable space, from impact fees entirely. The section defines 'impact fee' for this purpose as a fee under the state Mitigation Fee Act, Government Code § 66000(b), and a fee under the Quimby Act, Government Code § 66477, while excluding utility connection fees and capacity charges, which are addressed separately. A related exemption in subsection (h)(1)b keeps a JADU or an ADU under 500 square feet from counting as added assessable space under Education Code § 17620(a)(1)(C), so those small units are not subject to school impact fees either.

Only an ADU of 750 square feet or more triggers an impact fee at all, and even then the fee cannot be charged at the full new-dwelling rate: subsection (h)(1)c requires it be prorated by the ratio of the ADU's floor area to the primary dwelling's floor area, multiplied by the typical fee charged for a new dwelling. Utility connection fees follow a separate rule in subsection (h)(2): an ADU or JADU converted from existing space on a single-family lot generally needs no new utility connection or connection fee at all, while an ADU that does require a new connection is charged proportionately based on floor area or drainage-fixture units rather than the standard new-dwelling rate.