Mentmore Cottages

Built circa 1870 two semi-detached cottages at Mentmore, UK masquerade as one Mock Tudor style house.

Semi-detached housing (often abbreviated to semi in the UK, Canada and Australia, as in "three-bedroom semi") consists of pairs of houses built side by side as units sharing a party wall and usually in such a way that each house's layout is a mirror image of its twin. This style of housing, although built throughout the world, is commonly seen as particularly symbolic of the suburbanisation of the United Kingdom and Ireland, or post-war homes in Central Canada. Confusingly, this is sometimes colloquially called a duplex in New England, other parts of the United States, and most of Canada, a term used elsewhere for two apartments, one above the other.

This type of housing can be thought of as being a half-way state between terraced or row housing and single-family detached homes. Terraced housing is constituted by continuous row houses with open spaces at the front and back, while semi-detached houses have front, rear and any one side open spaces, and individual detached houses have open spaces on all sides.


During the 19th century, a father and son architectural partnership, the Shaws, drew up some of the very first designs for semi-detached housing in London. Examples of their work can be seen in Chalk Farm, North London. In the British housing boom of the 1920s and 1930s semi-detached houses sprang up in suburbs throughout the country, and were popular with middle class home owners who preferred them to terrace houses. The design of many of these houses, highly characteristic of the era, was heavily influenced by the Art Deco movement, taking influence from mock Tudor, chalet styles and even ship design.

In the immediate post-war years many council houses also followed the 'semi' format, giving many Britons a first experience of private garden space.



Edwardian Semi Detached Homes

Edwardian-era 'semis' in Dubbo, New South Wales. When new, the design of each side would have been identical. The embellishments on the right side of the building are more recent. The photograph offers a clear illustration of the separate title enjoyed by each property.

In Australia, a semi-detached house is a different form of real property title from a townhouse. A semi-detached house sits on a single property, owned in its entirety by the owner of the semi-detached house; a townhouse has a strata title or more recently known as a community title in South Australia. Semi-detached houses come only in pairs, whereas townhouses may number more than two, attached together. In Sydney, semi-detached houses still referred to as 'semis' were briefly popular at the beginning of the 20th century and many examples may be found in inner suburbs such as Drummoyne. However, this style quickly gave way to the 'modern' style of detached housing which allowed better motor vehicle access amongst other benefits.

United KingdomEdit

During the house price boom in the years to 2004 many UK property developers found they could create value by demolishing semi-detached houses and building two detached houses on the same site, often with a very narrow gap between the new units.[citation needed]


The semi-detached house was seen as a good fit for downtown Toronto's long, narrow lots early in the city's history, and their popularity was well established by the late 19th century. Victorian examples can be seen in areas such as The Annex, but the style was arguably most popular during the first few decades of the 20th century. They continued to be built well into the 1950s, often alongside detached types such as the bungalow. Red-brick semis are a common sight throughout downtown neighbourhoods and older suburbs; in fact, they are so typical of Toronto they could be seen as its answer to the New York City brownstone.

In Canada, some semi-detached homes have linked basements, such that the houses do not have individual basements. These are called linked semi-detached homes. This should not be confused with linked homes which appear detached, but there is a linkage below ground.

Cultural referencesEdit

  • "Semi-detached suburban Mr. James", written and performed by Manfred Mann, a song about a lost love marrying a philistine or babbitt living in a small suburban house, released in 1966 (Fontana TF 757), reached No. 2 in the UK charts.
  • "...semi by the sea" is part of a lyric from musician James Blunt in the song "Wisemen", released in March 2005; it was the second single off of his 10x platinum Back to Bedlam album.


es:Dúplex (vivienda) fr:Duplex (bâtiment) nl:Twee-onder-een-kap pt:Casa geminada sv:Parhus

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