The Urban Age conference is examining the wider issues raised by the provision of housing in mature cities such as New York, with a focus on the future of a number of key sites in the city. Each of these sites demonstrates an aspect of the pressures tending to squeeze the middle class out of the city centre, a movement which in turn puts pressure on other, more peripheral areas. Another apparently common tendency in every big city is for neighborhoods to become more locally homogeneous and segregated from the diverse social fabric of the wider city. It is a tendency represented in its most extreme and negative way by the gated community or walled city, and in a more positive ways by ethnic enclaves, or by creative artist districts, young singles and other communities of interest that cluster together.

The conference looks at how immigrant and minority populations fare in the New York housing market, a city with 65% of its people drawn from ethnic minorities, compared with 28.8% in London. Do negative neighborhood effects outweigh the positive effects of concentrations? What impact is this form of urban differentiation and fragmentation having on the cohesion of the city and the quality of urban life?

Assuming that such a tendency is not necessarily an entirely positive one, cities need to take steps to encourage the creation, or the safeguarding of built environments, that can support diverse neighborhoods and inclusive local communities. In particular, it is not only forms of tenure and questions of affordability that have a significant impact on these issues. The physical and spatial form of housing and urban design can serve to enhance the coexistence of various social groups – including families with children – that opt for “city life” over suburbanization.

The starting point in most discussions of urban design is the question of density. It has become something of a given that high density makes for vitality in a city, providing the sheer numbers of people in the concentrations needed to support everything from a mass transit system to schools, cinemas, public libraries and post offices. In New York City, gross residential density is 96 persons per hectare, while in London it is 45.6 persons. In New York 33.9% of households that have children under 18, compared with 28.6% in the latter.

High density cities are also regarded as better suited to reducing dependence on the private car, and thus bringing a range of environmental benefits. But it is not necessarily the case that all parts of a city should be equally dense. If high urban densities are considered a desirable goal, then so is homeownership and general housing affordability; these goals may not always be compatible. If that is the case, then we need to determine the best policy mix to achieve acceptable compromises between them. Is there such a thing as an optimum urban density? And how much variation in density should there be between dense urban cores and more sparsely developed peripheral areas?

In the context of a city with as dense an urban core as New York, and its competition for land between housing and industry, how much room is left for new or in-fill developments? This issue falls within the reach of local government to influence directly through re-zoning and by permitting the conversion of the city’s waterfront and industrial areas. The regulatory system in New York City certainly influences the city’s potential for growth. But what are its strengths in terms of providing city residents with the stability that communities need to flourish?

Authors: Deyan Sudjic and Miguel Kanai