<P> Houses commonly have only one or two floors . Buildings are often classified as low - rise, mid-rise and high - rise according to how many levels they contain, but these categories are not well - defined . A single - storey house is often referred to, particularly in the United Kingdom, as a bungalow . The tallest skyscraper in the world, Burj Khalifa, has 163 floors . </P> <P> The height of each storey is based on the ceiling height of the rooms plus the thickness of the floors between each pane . Generally this is around 10 feet (3.0 m) total; however, it varies widely from just under this figure to well over it . Storeys within a building need not be all the same height--often the lobby is taller, for example . Additionally, higher levels may have less floor area than the ones beneath them (e.g., the Willis Tower). </P> <P> In English, the principal floor or main floor of a house is the floor that contains the chief apartments; it is usually the ground floor, or the floor above . In Italy the main floor of a home is usually above the ground level, and may be called the piano nobile ("noble floor"). </P> <P> The attic or loft is a storey just below the building's roof; its ceiling is often pitched and / or at a different height than that of other floors . A penthouse is a luxury apartment on the topmost storey of a building . A basement is a storey below the main or ground floor; the first (or only) basement of a home is also called the lower ground floor . </P>

What is the first floor of a building
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