Bonus room

Bathrooms, technical rooms, laundry rooms or storage rooms/wardrobes do not typically satisfy requirements for permanent residence according to building codes

A bonus room, flex room, multiuse room or spare room (though the latter often means an extra bedroom) is a room created by remodeling or adding an addition that does not meet local building code definitions for traditional rooms, or is designed for multiple possible uses. For example, codes will typically require that a bedroom have a window and a certain number of electrical outlets. Such a room might actually be intended for sleeping, but will be described as a "bonus room" in rental and sales listings.