According to New York City’s Building Code, a story is the portion of a building between the “upper surface” of one floor all the way up to the upper surface of the floor above it (or, for the top story, from the upper surface of the floor to the top of ceiling joists or roof rafters).
That being said, it’s not always so simple figuring out what counts as a story and what doesn’t.Mezzanines, for instance, which are intermediate levels between the floor and the ceiling that take up less than 1/3 of the space’s area, aren’tconsidered stories. Additionally, while most people use the terms basement and cellars interchangeably, they couldn’t be more different as far as the Building Code is concerned, especially when it comes to counting stories. A basement, which has at least half of its clear height above ground, is counted as a story. Cellars, however, which have more than half of their clear height below ground, are not considered stories (and also aren’t considered habitable).