A storey (or story in American English) is any level part of a building that could be used by people (for living, work, storage, recreation, etc.). The plurals are "storeys" and "stories" respectively.
The terms "floor", "level", or "deck" can also be used in this sense, except that one may use "ground floor" and "ground level" for the floor closer to what is considered the ground or street level.〔(【引用サイトリンク】title=Story | Define Story at Dictionary.com )〕 The words "storey" and "floor" also generally exclude levels of the building that have no roof, even if they are used by people—such as the terrace on the top roof of many buildings.
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. The tallest skyscraper in the world, Burj Khalifa, has 163 floors. , the tallest planned skyscraper, Sky City, is planned to have 202 floors.
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 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 more spacious, for example. Additionally, higher levels may be smaller in area than the ones beneath (a prominent feature of the Willis Tower).
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").
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.
Split-level homes have floors that offset from each other by less than the height of a full storey. A mezzanine, in particular, is typically a floor halfway between the ground floor and the next higher floor. Homes with a split-level entry have the entire main floor raised half a storey height above the street entrance level, and a basement that is half a storey below this level. In Macy's Herald Square, there is a "one and a half" floor between the first and second, this can be considered a split level floor.
There are also multi-storey car parks, also known as parking garages.
Floor numbering is the numbering scheme used for a building's floors. There are two major schemes in use across the world. In one system, used in the majority of Europe, the ground floor is the floor on the ground and often has no number or is assigned the number zero. Therefore, the next floor up is assigned the number 1 and is the first floor. The other system, used primarily in the United States and Canada, counts the bottom floor as number 1 or first floor. The next floor up then becomes the second floor and so on.〔(Rick Steves' Europe through the back door 2011 )〕 In both systems, the numbering of higher floors continues sequentially as one goes up, as shown in the following table:
Each scheme has further variations depending on how one refers to the ground floor and the subterranean levels. The existence of two incompatible conventions is a common source of confusion in international communication, sometimes even between communities who speak the same language.
In all English-speaking countries, however, the storeys in a building are ''counted'' in the same way. Thus, for example, the phrase "a seven-storey building" would mean the same thing in Britain and in the US—namely, a building with seven covered floors, including one at ground level and six at higher levels, even though the topmost of those levels would be called "6th floor" in Britain and "7th floor" in the US. Some count mezzanines as storeys while some do not.〔(sameish - Which Floor is Which? )〕
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