Under the Statewide Building Code, all new dwellings, all residential additions and alterations involving living space, must have smoke detectors wired directly into the electrical system of the house and they must have a battery backup. Smoke detectors are required in each bedroom and on each level of the home, including the basement.
In new home construction, the detectors must be interconnected, so that they all sound simultaneously. Any alteration of an existing house, such as a family room addition or finishing a basement, will require the smoke detectors to be installed in these areas as per code. If an alteration of an existing house is to the entire house, then the smoke detectors must be installed in the same manner as new construction requirements.