Riverside County, CA Accessory Structures: ADU Impact Fees (2026)

070 of the Riverside County Code sets the fee framework for accessory dwelling units, junior ADUs, second units, guest quarters, MOG units and ranchets built in the unincorporated county. 22 and County Ordinance No. 659, the fee ordinances that fix the county's permit and inspection charges. On utility hookups, the code draws a line by unit type: an attached or interior ADU or junior ADU is not required to install a new or separate utility connection directly between the unit and the utility, unless the unit is built at the same time as a new one-family dwelling, as determined through the permitting process.

Guest quarters are barred outright from getting a separate utility connection. Detached ADUs, second units, MOG units and ranchets, by contrast, can be required to provide their own connection. 100 of the county's MSHCP local development mitigation fee chapter exempts accessory dwelling units and junior accessory dwelling units from that fee, but only to the extent the exemption is required under state law; second units and guest quarters get the same conditional exemption. 060. That fee is remitted to the Western Riverside County Regional Conservation Authority and must be paid before a certificate of occupancy or final inspection is issued on a non-exempt project.