Sonoma, CA Accessory Structures: ADU Impact Fees (2026)

040(J), Fees, sets the City of Sonoma's ADU fee structure in two parts. 040(J)(1)(a), "no impact fee is required for an ADU that is less than 750 square feet in size," a direct implementation of the state ADU statute's small-unit fee exemption. 040(J)(1)(b) requires any impact fee to be charged proportionately to the primary dwelling's floor area, calculated by dividing the primary dwelling's floor area by the ADU's floor area and multiplying by the typical fee for a new dwelling; the section specifically excludes water and sewer connection fees or capacity charges from this "impact fee" definition.

060(A)(1) does not need a new or separate utility connection to the ADU, and no connection fee or capacity charge applies unless the ADU or JADU is built together with a new primary dwelling. Any ADU or JADU not covered by that exception must have its own utility connection, subject to a connection fee or capacity charge proportionate to the burden it places on the water or sewer system, measured by floor area or drainage-fixture-unit values under the California Plumbing Code; that fee cannot exceed the reasonable cost of providing the service.

060(B)(2) lets the city charge an ADU permit processing fee, set by the planning and community services director and approved by city council resolution, to cover the cost of reviewing ADU permits and administering the ADU ordinance.