Aliso Viejo, CA Accessory Structures: ADU Impact Fees (2026)

Subsection (J) of § 15.14.080 applies to all Class 1 ADUs and JADUs and to Class 2 ADUs approved through the building permit or development review permit routes. Under (J)(1)(a), no impact fee is required for a JADU or for an ADU that is less than 750 square feet of interior livable space. The code defines "impact fee" as a fee under the Mitigation Fee Act (Government Code Section 66000(b)) and a fee under the Quimby Act (Government Code Section 66477), and states that it does not include any connection fee or capacity charge for water or sewer service.

Subsection (J)(1)(b) adds that a JADU or ADU with less than 500 square feet of interior livable space does not increase assessable space by 500 square feet for purposes of Education Code Section 17620(a)(1)(C), so it is not subject to school fees under Education Code Section 17620.

For an ADU of 750 square feet or more, any impact fee that is required must be charged proportionately in relation to the square footage of the primary dwelling unit. The code gives the formula as the floor area of the ADU, divided by the floor area of the primary dwelling, times the typical fee amount charged for a new dwelling.

Utility charges follow subsection (J)(2). JADUs and converted ADUs on a single-family lot are not required to have a new or separate utility connection, and no connection fee or capacity charge is required for them. When an ADU is built with a new single-family home, a separate utility connection and the normal connection fee and capacity charge for a new dwelling can be required. For other ADUs, any connection fee or capacity charge must be proportionate to the burden on the water or sewer system, measured by floor area or drainage-fixture units under the Uniform Plumbing Code, and the city's portion cannot exceed the reasonable cost of providing the service. The development review permit processing fee is set by city council resolution.