IRC R314: Smoke Alarms
IRC R314 says where smoke alarms go in a house: inside every bedroom, outside each sleeping area near the bedrooms, and on every story including the basement. In a new home the alarms must be hardwired with battery backup and interconnected so when one sounds, they all sound.
Smoke alarms are the cheapest life-safety system in a house and the one that saves the most lives. IRC Section R314 spells out exactly where they go and how they have to work, so a fire that starts while you sleep wakes you in time to use the exits. The rule is not "put one in the hallway." It is a specific set of locations plus an interconnection requirement that most homeowners do not realize their house needs.
Where R314 requires alarms
The code requires a smoke alarm in three kinds of locations: inside each sleeping room (every bedroom), outside each separate sleeping area in the immediate vicinity of the bedrooms (the hall outside the bedrooms), and on each additional story of the home, including basements and habitable attics. Here is the location language:
Smoke alarms shall be installed in each of the following locations: In each sleeping room. Outside each separate sleeping area in the immediate vicinity of the bedrooms. On each additional story of the dwelling, including basements.
How the alarms must work
Location is only half of R314. In new construction the alarms must be interconnected, so that when any one alarm detects smoke, every alarm in the house sounds. A fire that starts in a far bedroom has to wake a sleeper at the other end of the house, and a single beeping unit cannot do that. The alarms also draw primary power from the building wiring (hardwired) with a battery backup so they keep working in a power outage. Interconnection can be a hard wire between units or a listed wireless link.
There is one placement carve-out worth knowing: an alarm has to sit at least 3 feet from a bathroom with a tub or shower, because steam triggers nuisance alarms that get people to disable them.
What it means in practice
For example, a four-bedroom single-story custom home in Cave Creek needs a smoke alarm in all four bedrooms, one in the hallway serving them, and one in any additional living area that reads as a separate story or level, all wired together. Add a second story and you add at least one alarm for that level. The cost is small, but the interconnection wiring has to be planned during rough electrical, not added later.
How it connects
R314 is the early warning that makes the rest of the life-safety chain work. It pairs with IRC R315 carbon monoxide alarms , which often share a combination device, and with IRC R311 means of egress , the safe path the alarm sends you to. The fire separation in IRC R302 fire-resistant construction slows the fire while the alarm gets everyone moving.
Edition note
The required locations (each bedroom, outside each sleeping area, each story) and the interconnection rule are stable across the 2018, 2021, and 2024 IRC. The 2024 edition adds provisions around alarm replacement age and certain listing standards, but the placement and interconnection numbers above do not change. Confirm your city's adopted edition on the Arizona building code editions by city page.
Source
Read the section on the official ICC site: 2021 IRC R314.3 on codes.iccsafe.org . The I-Codes are copyrighted; only the short location clause is quoted here.
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