Everyone knows that smoke alarms are important and save lives, but many are confused about where they should be installed. It can be tricky, since the manufacturer’s recommendations, state, and local requirements often don’t agree. The advice given here is based upon the California Residential Code (CRC). Before buying your smoke alarms, please read THIS to learn the importance of photoelectric type smoke sensors.

Required Locations
For decades, smoke alarms have been required on all homes and dwelling units without exception. It doesn’t matter if you have a new home or an old home – they are required by California state law. So where do they need to be installed? Section R314 of the CRC requires smoke alarms:

  1. In each sleeping room
  2. Outside of each sleeping area in the immediate vicinity of the bedrooms
  3. On each additional story of the building, including basements and habitable attics
  4. At least 3 feet horizontally from a bathroom door (if possible)

While the above locations are the minimum required, you can always add them in more locations if you like.

Alarm Placement
The ceiling is always the preferred location for smoke alarms, as hot air rises. While most of the installation instructions allow placement on a wall, the ceiling is still preferred. The area right outside a bathroom should be avoided since the steam from bathing can cause false alarms. It is important to avoid putting alarms in the “dead space” at the wall / ceiling intersection, as the smoke may bypass this area initially. The same thing applies to the peak of a vaulted ceiling.

Immediate Vicinity
So while the residential code require alarms “outside of each sleeping area in the immediate vicinity of the bedrooms” – the question becomes: what is the immediate vicinity? No definition is given, so you’ll have to use your best judgement. If the sleeping areas are really far apart, or if there is a door that separates the sleeping areas, it’s best to have multiple smoke alarms.

Hardwired Alarms
Some buildings have hardwired alarms, which will make moving or replacing these alarms much more difficult. The process is not that different than switching out an electrical outlet or switch, but if you have any doubts, it’s always best to get an electrician.