Last edited 15 Oct 2020



The term ‘apartment’ refers to a self-contained housing unit that occupies only part of a building, typically, on a single level. It is generally associated with North American real estate, although apartments have been common as far back as the Roman times. The term itself is thought to have originated in the mid-17th century, from the French word ‘appartement’ derived from the Italian ‘appartamento’ in turn derived from ‘appartare', meaning ‘to separate’.

In North America, apartments are typically leased. Residential blocks in which the residents own their accommodation are generally referred to as ‘condominiums’.

The term ‘apartment’ is sometimes considered to be synonymous with the term ‘flat’ commonly used in the UK. However, Approved document B, Fire Safety, Volume 1 Dwelling houses, defines a flat specifically as; 'a separate and self-contained premises constructed or adapted for use for residential purposes and forming part of a building from some other part of which it is divided horizontally.' and suggests that this '...includes live/work units, i.e. a flat intended to serve as a workplace for its occupants and for persons who do not live on the premises.’

For more information see: Flat definition.

In the UK, the term ‘duplex’ refers to an apartment (not a house) that includes two floors of accommodation, joined by an internal staircase. Historically, this would have been referred to as a maisonette, but the term duplex has become increasingly popular because of its perceived Americanism, and is generally applied to apartments with a more modern design, whereas a maisonette might be more traditional.

For more information see: Duplex.

The term 'penthouse' is used to describe an apartment on the top floor of a high-rise building. According to the New York City building code, a penthouse is ‘ enclosed structure on or above the roof of any part of a building, which is designed or used for human occupancy.’ Penthouses are frequently the largest, most luxurious, and therefore the most expensive, apartments in a building.

For more information see: Penthouse.

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