San Jacinto, CA Building Safety: Fire Sprinkler Requirements (2026)

Subsection F.3 of § 17.405.060 ties the sprinkler question for every accessory dwelling unit and junior accessory dwelling unit to the primary residence. If sprinklers are required in the primary residence, they are required in the ADU or JADU. The reverse does not apply: constructing an ADU or JADU does not trigger a requirement to install sprinklers in the existing primary dwelling, so an owner adding a unit to an older house is not forced to retrofit the house.

The sprinkler rule sits inside a package of building and fire safety conditions. Under Subsection F.9.a, all ADUs and JADUs must comply with all local building code requirements. Under F.9.b, building an ADU is not a Group R occupancy change under Section 310 of the California Building Code unless the building official makes a written finding, based on substantial evidence in the record, that the ADU could have a specific, adverse impact on public health and safety. A Class 1 ADU converted within existing space must have side and rear setbacks sufficient for fire and safety, as dictated by applicable building and fire codes. Where landscaping screens a Class 2 ADU from the street, plants with a mature height of four feet or more must sit at least three feet from the building to ensure adequate fire access.

Every ADU and JADU needs an ADU permit and a building permit, so the sprinkler question is answered through those permits. The City has 15 business days to determine completeness and 60 days from a complete application to approve or deny. No certificate of occupancy for an ADU or JADU can be issued before the certificate for the primary dwelling, with a limited exception for a detached ADU after a state-declared emergency proclaimed on or after February 1, 2025 that substantially damaged or destroyed the primary dwelling, once the ADU has passed all required inspections.