Redwood City, CA Fire Regulations: Smoke Detectors (2026)
Key Facts
- Trigger
- Home has sprinklers under Fire Code 903.3.1.2/.3
- Requirement
- Interconnected smoke alarms activate with sprinklers
- Alternative
- Horn-strobe device, one per floor, all sleeping rooms
- Exterior alarm
- Audible device tied to sprinkler water flow
- Enforced at
- Final fire inspection / occupancy approval
Summary
Redwood City's amended Fire Code section 903.4.2 requires every home with a required automatic fire sprinkler system to activate all of its interconnected smoke alarms when the sprinklers go off, on top of an exterior water-flow alarm bell tied to the sprinkler system itself.
903.4.2 Alarms. One exterior approved audible device, located on the exterior of the building in an approved location, shall be connected to each automatic sprinkler system. Such sprinkler waterflow alarm devices shall be activated by water flow equivalent to the flow of a single sprinkler of the smallest orifice size installed in the system. In addition, for automatic sprinkler systems installed under Section 903.3.1.2 or 903.3.1.3, activation of all of the interconnected single station smoke alarms throughout the residence is required. An acceptable alternative to interconnection to the smoke alarms is the installation of horn strobe devices in locations that will provide adequate notification to all sleeping rooms with at least one notification device per floor. Where a fire alarm system is installed, actuation of the automatic sprinkler system shall actuate the building fire alarm system. Visible alarm notification appliances shall not be required except when required by Section 907.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Zoning Code: Supplement 29 | City Code: Supplement 61 Update 1).
Full Breakdown
2 to require one exterior approved audible device on the building, connected to the automatic sprinkler system, that activates when water flows equivalent to a single small-orifice sprinkler head. 18 requires most new and retrofitted residences to be equipped, activation of the sprinkler system must also trigger every interconnected single-station smoke alarm throughout the residence. Builders may substitute horn-strobe notification devices in place of interconnecting the smoke alarms, but only if at least one device is installed per floor and the devices give adequate notice to every sleeping room.
Where a separate fire alarm system exists in the building, sprinkler activation must also actuate that fire alarm system. The section limits when visible (strobe) alarm notification appliances are mandatory: they are required only where section 907 of the Fire Code separately calls for them, not as a blanket rule for every sprinklered residence.
Violations & Fines
A residence built or retrofitted with a required sprinkler system that lacks the interconnected smoke alarm activation, or an equivalent horn-strobe substitute reaching every sleeping room, fails final fire inspection and cannot receive occupancy sign-off. Because section 903.4.2 carries no standalone fine, a violation falls under Redwood City Code section 1.7's general penalty: a misdemeanor punishable by up to $1,000 in fines, six months in jail, or both.
Frequently Asked Questions
Does Redwood City require smoke alarms to activate when my sprinklers go off?
Can I skip interconnecting my smoke alarms?
Is a separate exterior alarm bell also required?
Sources & Official References
Other rules in Redwood City
California rules heatmap·Compare Redwood City to another location·View the California fire regulations overview
See something wrong?
Help us keep this page accurate. If you notice an error or outdated information, let us know.