Question regarding what the code is on smoke/CO alarms is on additions.  As part of a minor addition to a 1950s home, my sparky says that he needs to install hardwired/interconnected smoke alarms everywhere (in bedrooms, halls, basement, etc) and I’m questioning him.  Is there any thing in the code regarding grandfathering this in or using interconnected, battery operated (bluetooth/Next type) alarms so we’re not running wires all over the house? The addition is less than 300 sf and is only a kitchen, half bath and pantry/laundry.  The rest of the dwelling (single floor ranch) won’t be touched. Seems like overkill. Anybody know the code on this one?