‘My pink half of the drainpipe keeps me safe from you’: so sang the Bonzo Dog Doo-Dah Band about the ambiguous pleasures of the semi-detached house. This type - the Doppelhaus in German, or the duplex, as it is known in much of North America - is England’s great gift to world architecture, and to comedy. A symbol of middle-class aspiration, conservatism and compromised individualism, it is the British modern domestic type par excellence, even though it has more frequently appeared in Tudorbethan fancy dress than high-tech garb. This may make our metropolitan readers wince, but it is undeniable that the semi is the dream (and actual) home of vast numbers of people: it is the most common dwelling in the UK, where it houses one third of the population. Why should this be? Where did the semi come from? And, in the midst of an acute housing crisis and widespread calls for ‘sustainability’, what can we - should we - do about this bipolar beast that gobbles up space and people’s hearts along with it?

The first semis were born a world away from the bypass road with which they are associated today: some of the earliest examples were built in the countryside by 17th-century landowners wishing to house their labourers cheaply while making their estates look as grand as possible. There is something in this deceptiveness, present right from its inception, that makes the semi an uncomfortable proposition to architectural moralists; it is mass housing in manorial masquerade, built false consciousness, feudal atavism. But why shouldn’t people live as if they were better off, in a house pretending to be something it isn’t - and why not stick blackened beams on the front while you’re at it? Why not, so long as it makes you happy? But then, you may ask, is this half-happiness enough?

From its rural birthplace, the semi was smuggled into town disguised as a Georgian villa - so although we associate Georgian design with the acme of tasteful British vernacular housing, it is also the origin of its vilified Siamese twin. But then the Georgians were great speculative volume builders, so it should come as little surprise to find that they invented this enduringly marketable commodity. When John Claudius Loudon published his own design for a semi in his widely read 1838 book The Suburban Gardener, and Villa Companion, the idea spread. Loudon included neurotically detailed advice on making two more modest homes appear as one: the two front doors were hidden down opposite sides, to complete the illusion of wholeness. But semis only fell subject to widespread odium further into the 19th century, as the type was adapted to the age of the railway and the expanded middle classes. In the London suburb of Bedford Park, much mocked at the time for its artistic pretensions, Richard Norman Shaw dressed the semi in vernacular clothes (from 1877). In doing so he prepared it for the developers of the interwar years, and their customers, the lower-middle classes. Bedford Park was also the semi’s launch pad to the wider world (if we are to follow Pevsner’s argument), via Muthesius’s influential 1904 book Das englische Haus. Norman Shaw had solved the problem of the small, middle-class house, Muthesius averred - in his opinion the crucial issue in housing of the day. And indeed, with his light-filled bay windows and economical, repeatable, yet individual-looking types, he had helped develop a form of mass housing which eminently served the requirements of a new class.

Across the Channel, the semi was regarded as a valid type by even the most austere Modernists. Le Corbusier’s famous house at the Weissenhofsiedlung was semi-detached, although it looks more like an escaped segment of mass housing - a polar-opposite example of the British semi’s dissembling tendencies. Gropius’s 1925 Meisterhäuser for the Bauhaus teachers were all Doppelhäuser (his own being the only single-family dwelling); Gropius took the unusual step of rotating the second dwelling, which had an identical floor plan to the first, by 90 degrees, thus returning by a circuitous route to the Georgian semi that looks like one villa, even if his version didn’t look like much else that had come before. Further afield, several of Frank Lloyd Wright’s ‘American System-Built Homes’ in Milwaukee (1917) are duplexes, the only examples of the type in his oeuvre. The greater availability of space made single-family homes more affordable and more prevalent in suburban USA.

Meanwhile in Britain the car spread the suburbs ever further from the city, and with them marched the semis. These came in a variety of Shavian Artsy-Craftsy styles. ‘All over the country the latest and most scientific methods are being utilised to turn out a stream of old oak beams, leaded window panes and small discs of bottle-glass, all structural devices which our ancestors lost no time in abandoning as soon as an increase in wealth and knowledge enabled them to do so.’ This is of course the voice of Osbert Lancaster, the funniest critic of the semi (‘bypass variegated’ as he called it) and the most self-revealing, for it is often the fear of the established, educated and embattled middle class that speaks in their ridicule of the aesthetic preferences of the rising lower-middle. Lancaster was, to be fair, explicitly arguing from a Modernist position of truth-to-materials; nevertheless he was equally scathing about Modernist houses, of which there were an increasing number in Britain at that time. Well-known pioneering settlements such as Thomas Tait’s houses for Crittall employees at Silver End (1927-28) and the Bata factory estate in East Tilbury (1932-35) included several white, cuboid semis. These are unusual in that they attempt to adapt the type - which caters to the same Modernist desires for light and air as Zeilenbauten - to the needs of the proletariat, rather than the petit bourgeoisie, by clothing the semi in workers’ overalls. A similar union was attempted in the form of Herbert Welch’s ‘suntrap semis’ on the Portsdown Estate at Edgware (1932), albeit to different ends. These houses, with their hipped roofs plonked onto Deco bodies, were intended by the developer to embody the values of Modernism, but with public appeal, and their visual distinction from the Tait or Bata houses can be attributed to the fact that they were commissioned by a speculative builder and not a paternalistic industrialist. More aesthetically satisfying compromises have since been found along the road to Postmodernism: in Eric Lyons’ many estates for Span Developments, for instance.

The semi continues to appeal, both to volume builders and to more autonomous architects, such as Stephen Taylor (AR May 2014). Most importantly, it still appeals to the public. There are countless people who can’t or don’t want to pay for a freestanding home, and yet wish to partake of the very real material advantages of semis over terraced houses or flats: they offer access to their (usually larger) gardens without having to pass through the house (this space also comes in handy for parking or lean-to garages), and they have natural light on three sides. They are easily modified, and therefore offer the satisfaction that comes from having visibly made your house your own. But although semis cater to our individualism, there is something questionable about the way they occupy space; their effects on planning (few developers are as sensitive to this issue as Eric Lyons); and their energy-inefficiency. The latter problem is not intractable and, periodically, sensitive attempts have been made to rework the semi for current needs, for instance, Sergison Bates’ winning entry for a competition held by a housing association to design a prototype for mass production. Nevertheless, as the housing crisis deepens, higher-density types than the semi are necessary if we are to house growing urban populations within the extant perimeters of our cities.

The cleavage of the semi exposes the tension at the heart of housing, which is at once commodity and dream; an ontological need for dwelling-in-the-world, and an excuse to go shopping at IKEA. It expresses both the desire for individual freedom, ostensibly protected by the privacy of the family circle, and the inescapability of socio-economic bonds; we may dream of castles in the sky, but back down on earth we can only afford half a plot carved out by a volume builder next to a roaring motorway. Nietzsche called wit ‘the epitaph of an emotion’, and perhaps that’s where the genuine humorousness of the semi is located: it expresses with painful clarity the irreconcilability of dream life and real life under present conditions.