Fresno County, CA Building Safety: Fire Sprinkler Requirements (2026)

The rule is a single, direct sentence inside the county's general accessory dwelling unit standards. 030(B)(6)(c) states: "Fire Sprinklers. 030, whether attached, detached, or converted. Because most existing single-family homes in the unincorporated county were built before automatic fire sprinklers became a standard California Residential Code requirement, most ADUs added to those older homes are not required to add sprinklers solely because of the new unit. The determining factor is whether the specific primary dwelling on the parcel is required to have sprinklers, which turns on the edition of the building code in effect when that primary dwelling was permitted, not on the ADU's size or configuration.

This mirrors state ADU law's intent to avoid using fire-code retrofits as a barrier to ADU construction, while still requiring sprinklers in an ADU built alongside a new primary home whose own permit already requires sprinklered construction.