Semi-detached

A semi-detached house (often abbreviated to semi or semi-D) is a single family dwelling house built as one of a pair that share one common wall. Often, each house's layout is a mirror image of the other.

Semi-detached houses are the most common property type in the UK. They account for 32% of UK housing transactions and 32% of the English housing stock as of 2008. Between 1945 and 1964, 41% of all properties built were semis, but after 1980 this fell to 15%.

Housing for the farm labourer in 1815 was typically a one-room shed with an outshot for a scullery and pantry, and two bedrooms upstairs. The house would be of brick, stone if it occurred locally, or cob on a wooden frame. They were unsanitary, but the biggest problem was they were simply too few. Population was increasing, and after the enclosure acts, labourers could not find spare land to build their own homes, so it fell to the landowner or the speculative builder.

Estate villages followed vernacular patterns, but this changed to adopting model designs from pattern books. By the turn of the 18th century the landowners chose a "picturesque" style. They built double cottages as a means of reducing cost. Smith in 1834 wrote "this species of cottage can be built cheaper than two single ones, and, in general, these double cottages are found to be warmer and fully as comfortable as single ones".

While there had been a huge increase in the population of the rural counties there was a greater shift in the population from the impoverished land to the large towns and London. At the same time, society was restructuring, with the labouring classes dividing into artisans and labourers. The cities offered labourers housing in tenement blocks, rookeries and lodging houses, and philanthropic societies turned their attention towards them. The rural "Labourers’ Friend Society expanded in 1844, and as a result of the various reports on the housing conditions of the urban working classes, it was reconstituted as the "Society for Improving the Condition of the Labouring Classes". The earlier designs they published had been for semi-detached dwellings but the first properties they build were tenements and lodging houses. In their 1850 publication 'The Dwellings of the Labouring Classes', written by Henry Roberts, there were plans for model 'semi-detached'cottages for workers in towns and the city. In 1866 the Metropolitan Association for Improving the Dwellings of the Industrious Classes, founded by Rev Henry Taylor, built Alexander Cottages at Beckenham in Kent, on land provided by the Duke of Westminster. This development initially comprised 16 pairs of semis but two years later they had built 164 semis.

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