In architecture and city planning, a terrace, rowhouse, or townhouse (though the latter term can also refer to patio houses) is a style of housing in use since the late 17th century, where a row of identical or mirror-image houses share side walls. The first and last of these houses is called an end terrace.

In the United Kingdom

The term terrace was borrowed from garden terraces by English architects of the late Georgian period to describe streets of houses whose uniform fronts and uniform height created an ensemble that was more stylish than a "row". The "row", as in the 16th century "Yarmouth Rows" in Great Yarmouth, Norfolk, was a designation for a narrow street where the building fronts uniformly ran right to the property line.

In England, the first streets of houses with uniform fronts were built by the Huguenot entrepreneur Nicholas Barbon in the rebuilding after the Great Fire of London, but Paris had led the way in the Place des Vosges (1605 ? 1612). In Parisian squares, central blocks were given discreet prominence, to relieve the fa?ade, but the Georgian idea of treating a row of houses as if it were a palace front, giving the central houses columned fronts under a shared pediment, appeared first in London's Grosvenor Square (1727 onwards; rebuilt) and in Bath's Queen Square (1729 onwards) (Summerson 1947).

Early terraces were built by the two John Woods in Bath and under the direction of John Nash in Regent's Park, London, and the name was picked up by speculative builders like Thomas Cubitt and soon became commonplace.

By the early Victorian period, a terrace had come to designate any style of housing where individual houses repeating one design are conjoined into rows either long or short. The style was used for workers' housing in industrial districts during the great industrial boom following the industrial revolution, particularly in the houses built for workers of the expanding textile industry. The terrace style spread widely in the UK, and was the usual form of high density residential housing up to World War II, though the 19th century need for expressive individuality inspired variation of facade details and floor-plans reversed with those of each neighboring pair, to offer variety within the standardized format.

In the UK terraced industrial district housing has enjoyed huge price rises since around 2001, with prices in most areas (outside London) having more than tripled by mid-2005. In affluent areas terraced houses are often called 'townhouses'. In the 1960s and 1970s areas of affordable terraced housing were often quickly colonised by artists, gay men and young professionals, this being the early stages of the gentrification that happened in parts of many British cities.

In 2005 the English Heritage report Low Demand Housing and the Historic Environment found that repairing a standard Victorian terraced house over thirty years is around sixty-percent cheaper than building and maintaining a newly-built house. In a 2003 survey for Heritage Counts a team of experts contrasted a Victorian terrace with a house built after 1980, and found that:

"The research demonstrated that, contrary to earlier thinking, older housing actually costs less to maintain and occupy over the long-term life of the dwelling than more modern housing. Largely due to the quality and life-span of the materials used, the Victorian terrace house proved almost ?1,000 per 100m2 cheaper to maintain and inhabit on average each year."

In Australia

Terraced housing was introduced to Australia from the United Kingdom in the nineteeth century. Large numbers of terraced houses were built in the inner suburbs of large Austalian cities, particularly Sydney and Melbourne, mainly between the 1850s and the 1890s. The beginning of this period coincided with a population boom caused by the Victorian and New South Wales Gold Rushes of the 1850s and finished with an economic depression in the early 1890s. Detached housing became the popular style of housing in Australia following Federation in 1900.

Terraced housing in Australia ranged from expensive middle-class houses of three, four and five-storeys down to cheaply built single-storey houses in working-class suburbs. The most common building material used was brick, often covered with stucco, but the cheapest houses, particularly the single-storey ones in Melbourne, were often built of weatherboards.

In the first half of the twentieth-century, terraced housing in Australia fell into disfavour and the inner-city areas where they were found were often considered slums. In recent decades these inner-city areas and their terraced houses have been gentrified.

In The US

In New York City, a large apartment building occupying a full city block, London Terrace, finished in 1930/1931 capitalized on the earlier, more stylish connotation. Terrace housing in American usage generally continued to be called townhouses in the United States, with a distinctive type found in New York City, among other cities, called a brownstone. In Philadelphia and Baltimore, they are simply called rowhouses, and are very common. In much of the Southern United States, particularly in Maryland, they are referred to as rowhomes. The oldest continuously occupied road in America, Philadelphia's Elfreth's Alley, is lined with rowhouses.