PREVI-Proyecto Experimental de Vivienda-an experimental district collectively designed by a generation of radical avant-garde architects who converged on Lima (Peru) in the late 1960s, was a pioneering attempt to reconcile the conflicting forces of informal growth and top-down planning.

In 1965, Peru's architect-president Fernando Belaunde Terry began consultations for a social housing program that would regulate the unstoppable flow of people seeking an urban destination (in the mid-1960s, the informal city, with its barriadas, seemed to have overwhelmed the "urbanized" part of Lima). Under the leadership of Peter Land, and with the support of the United Nations, the project for an experimental neighborhood was born; it involved the best radical avant-garde international architects chosen from among those who had a solid reputation for social housing. These architects were invited to participate in the creation of this dense urban college. All of them had been involved in the most interesting experiments in social housing in the early '60s, for example, Runcorn New Town Housing by James Stirling, the house-capsule for Nippon Prefabrication Co. by the Metabolist group, Tube Housing by Charles Correa, which became a model for the Indian region of Gujarat, or Cite Horizontal in Casablanca by Georges Candilis, who had collaborated with Le Corbusier at the L'Unite d'Habitation, Marseille.

Development

In PREVI, 13 internationally renowned architects, along with as many Peruvian architects, were commissioned to develop a model neighborhood of 1,500 dwellings to develop prototypes of urban housing that would internalize programs for any future transformation. Thus each unit contained the terms of its own growth. This was perhaps the first act that recognized the value of the dynamics of growth adopted in the informal slums. In contrast to a growth model based on large, out-of-scale gestures-from megastructures to gigantic superblocks-the PREVI experiment fielded new dynamics based on a model of low-rise, high-density housing. When, in October 1968, a military coup led to the overthrow of the president-architect who had promoted the PREVI project, the involvement of the United Nations prevented the project's cancellation. The jury met in 1969 and, while having chosen the winning projects (the international groups selected were Kikutake-Kurokawa-Maki, Atelier 5 and Herbert Ohl), resolved to initiate the construction of all but two of the proposals. In 1974, the first phase of 500 units was finally built and left to its fate of growth and progressive oblivion. In the north of Lima is a housing estate that could have changed the face of cities in the developing world. Its residents go about their lives feeling lucky that they live where they do, but oblivious to the fact that they occupy the last great experiment in social housing. If you drove past it today, you might not even notice it. And yet the Proyecto Experimental de Vivienda-or PREVI for short-has a radical pedigree. Some of the best architects of the day slaved over it. Now it is largely forgotten.

PREVI was the product of exceptional conditions. In the 1960s, the population of Lima was growing so fast that government housing schemes were proving woefully inadequate. Instead, people were building their own homes in informal barriadas, which today account for more than half of the city. In 1966, President Fernando Belaunde, who was also an architect, held an international competition in conjunction with the UN to devise a solution to the city's housing problem. The list of participants reads like a roll call of the 1960s' avant-garde: James Stirling, Aldo van Eyck, the Metabolists, Charles Correa, Christopher Alexander and Candilis, Josic and Woods. These are only the most famous. There were 13 international teams and 13 Peruvian-it was a housing Olympiad of sorts. Never again did so many prominent architects weigh in on the issue of social housing. The profession disengaged, eventually to discover the museum as the pinnacle of its ambitions.

Impact and consequences

That was the genius of PREVI: it was designed as a platform for change. The houses were not the end but the beginning, a framework for expansion. It was revolutionary. Of course, there was a tradition of the working class modifying their modernist offerings, as Le Corbusier discovered to his chagrin in Pessac, but it was never intended. The prevailing solutions to mass housing, the tower, and megablock, were singularly inflexible, and they simply couldn't be built fast enough or cheap enough. The barriadas, however, were starting to impress architects with their home-grown ingenuity, and PREVI was conceived as a formal version. The competition was geared towards low-rise, high-density concepts, and the architects were flown in to study the tvvv. Come 1970, after choosing three nominal winners-the Metabolists, Atelier 5 and Herbert Ohl-the judges decided to build all of the entries (except, ironically, Ohl's, which turned out to be too difficult to realize). The first pilot scheme would consist of 500 houses so that the designs could be fully tested on the ground, and in the second phase, the best would be rolled out by the thousand. Except the second phase never happened.For that reason, many considered PREVI a failure. Imagine investing in 24 different designs and construction methods-from brick to prefabricated concrete panels-in the hopes that the economies of scale would make up for it when the scheme was standardized. In the end, PREVI became an anomaly: a housing laboratory containing so many design ideas, that was so diverse and adaptable that it can probably never be repeated.

PREVI may have been largely forgotten but the lessons have not been lost. It just took 30 years to learn them. Today, there is a new orthodoxy emerging, at least in Latin America, that says housing should be built with a view to expansion and adaptation. Chilean practice Elemental's "half a house" model, deployed at the Quinta Monroy housing in Iquique, is the descendant of PREVI. Although in many ways it is not fair to compare PREVI with the much humbler Quinta Monroy, the comparison is rather eloquent on the situation in which architects engaged in social housing now operate. While building someone "half a house" is an ingenious solution to an extreme problem, it also reveals the lack of wholehearted government support that architects have today compared to that idealistic moment in Belaunde's Peru. The pragmatic compromises made by dedicated architects such as Elemental reflect a weakening of ideology and the failure of the state. And as governments have neglected their social responsibilities, architects have courted private patronage. The closest we have come in recent times to a generation-defining housing competition is Ordos 100, a vanity project by a Chinese billionaire in an uninhabited patch of Mongolian desert.

There are signs, however, that the tide may be turning. If PREVI marked the shift from a dogmatic modernist approach to housing the poor to one that capitalizes on the evolutionary, organic nature of informal settlements, that ethos has now been mainlined by a new generation of socially motivated architects such as Urban Think Tank, Jorge Mario Jauregui and Elemental of Alejandro Aravena. And in them, Aldo van Eyck, and Georges Candilis, and Shadrach Woods et al finally have their successors.