The word “densification” conjures images of scores of city dwellers, all crammed into homes the size of rabbit hutches. But many urbanists argue that, done correctly, denser cities make better places to live and work. So, what exactly is “good” density, and how do planners and placemakers achieve it?
George Bull, Freelance journalist
10 May 2018
Denser cities have the potential to be more productive, more innovative and more energy self-sufficient than their sprawling, low-density counterparts. This is the view of a growing number of urban theorists, planners and policymakers who argue that designing for density is critical if we are to create liveable, prosperous cities.
But despite its merits, public advocacy for density is low: for many it brings to mind crowded tower blocks and a loss of privacy. Is there a “perfect density” ideal into which everyone can buy?
“Everyone in the built environment seems to be convinced about density,” says Lisette Van Doorn, CEO of Urban Land Institute Europe, “but there is still a lot of discussion about how it should look.” This is partly because density itself is not the goal, she adds. It is the means: whether to enable a growing city like London to meet the demands of the sharing economy, or a shrinking city such as Dresden to manage decline, integrate its populations and recapture its buzz.
A city’s approach to density really depends on what one is trying to achieve, says Vishaan Chakrabarti, founder of the Practice for Architecture and Urbanism in New York, and author of A Country of Cities: A Manifesto for an Urban America. “In my book, I talk about 30 units per acre, but that is based on one metric, which is to support mass transit.”
Most city-dwellers want good public transportation links and walkable neighbourhoods, but often decry density, assuming it means high rise. Currently, only 4% of Americans live at the kind of density Chakrabarti is proposing, compared to 61% who live in the equivalent of a detached house.
“Height and density are by no means the same,” he says. While a minimum density of 30 units per acre is necessary to support a rail-based mobility system – the Tube or a light-rail network, for example – people should not find that a very scary number: “It’s not big skyscrapers, it’s townhouses and brownstone buildings – the densest parts of Manhattan or Hong Kong are three, four, five times that.”
Another assumption that Chakrabarti rejects is that density is synonymous with the destruction of local character. Some of the densest urban cores in the world are places famous for their sense of place and “they’re only six stories tall”. These are the so-called high-density, low-rise urban areas such as the Eixample district of Barcelona and the West Village in New York. Or between the fifth and sixth arrondissements in Paris, which houses up to 26,000 people per square kilometre.
This is not to say that Chakrabarti thinks skyscrapers are inherently “bad density”. One of the reasons fewer high-rise, low-density developments are built today is because they don’t get a lot of light or views, he says. The packed skylines of east Asian cities are often lazily written off as examples of unchecked development by urban planners, ignoring their achievements with mass transit and environmentalism. For example, the Seoul Metro serves 7 million passengers a day, while Hong Kong has one of the lowest rates of energy consumption per capita in the world.
The important thing to focus on, Chakrabarti adds, is not how high to build, but how to better distribute density. “One of the solutions that we should be looking at more is the idea of a big city that has different villages within it – places where you can work as well as live.”
Until relatively recently, New York has been the opposite of this – a so-called hub-and-spoke city with just a few downtown areas. But it is now undergoing a resurgence in densification in smaller neighbourhoods. Business districts are starting to disseminate and high streets are proliferating across the city. People now go to work in downtown Brooklyn, or live in Lower Manhattan.
By creating different centres within one city – or even by connecting up smaller cities in a single metro area – this polycentric model acts as a brake on so-called peak density, where everything happens in one place. Instead, you get an average density, which keeps the city at the human scale.
Ensuring these centres are mixed-use, with good public transport links, is crucial if planners are to avoid the mistakes of the past, Van Doorn asserts: decades on, isolated, single-use developments, such as La Défense in Paris and London’s Docklands, are still to shake off their reputations as business ghettos. And creating 24-hour destinations that can cater to a mix of population groups also helps to build in resilience.
A robust public transport system is necessary to facilitate the polycentric model, giving cities nodes around which to densify. This requires a level of public investment that is beyond some cities. Here Van Doorn praises London’s approach to financing infrastructure by offsetting the cost against land values, as it has done with Crossrail. To fund the cross-city rail link, the government calculated the potential increase in value to existing and new developments along the route and is capturing the uplift through business rates, Stamp Duty Land Tax and other development taxes and contributions. “Essentially densification pays for it,” says Van Doorn. “Lots of cities are now looking at that approach.”
Building good density also requires good public relations. The ULI’s Density Dividend report, published in 2015, found that for nearly all cities, “failed 20th-century densification projects linger in the collective public memory as places of danger, overcrowding, anxiety or boredom”. Those cities that have been successful in changing perceptions have a compelling story about their future – such as Stockholm’s “Capital of Scandinavia” brand and London’s strategic vision to become “the best big city in the world”.
For Chakrabarti and Van Doorn, designing for denser cities, not expanding them at their edges – where 90% of America’s housing stock has been built since the 1940s – is the 21st-century planner’s raison d’etre. But not everyone shares this view. “I call them the density lobby,” says Joel Kotkin, author and fellow in urban studies at Chapman University, California, referring to what he sees as a convenient narrative for a coalition of interests.
“If we give people a choice [of where to live], then that’s perfectly legitimate. But the problem is that densification has become a religion – everything is judged on it versus the reality of what people want. And the reality is that most people over the age of 30 want a single-family home or a townhouse; most don’t want to be perpetual apartment dwellers” - Joel Kotkin, author and fellow in urban studies, Chapman University, California.
He points to US census data that shows the population of 20- to 29-year-olds in core areas of Chicago and Portland has been in decline since 2010, while Boston and Los Angeles have been losing millennials since 2015.
In Kotkin’s view, the only people in this demographic able to get the most out of dense city living are those who also have the money to escape it on a regular basis. In this way, pro-density arguments cannot be decoupled from income. “The class bias is huge. It’s fine if you can afford to have a place in [New York] city and a house in the Hamptons.”
Chakrabarti would counter that this argument misses some of the more holistic cost savings of denser living, such as the reduced heating and cooling costs that come from people living more closely together in smaller spaces. “Low-density areas are actually quite expensive. For example, they tend to be car dependent, but for a person on a lower income, the running costs of a car alone can be a costly albatross.”
Ultimately, though, Kotkin has a point: the economics of Chakrabarti’s 30 units per acre provides enough density to support a subway, but to build affordable housing in a society where most development is done by the private sector, it would need to be higher. Possibly a lot higher. Cities that want the benefits of good density, of train riders and tax receipts that support public transport systems and green spaces, have to think deeply about what they want to achieve. As Van Doorn says: “You cannot seek density if you are pushing people out of the city.”
Whether it is a shrinking city that needs to consolidate or a fast-growing city that needs to accommodate more people, businesses and demographics, there is a pressing need to use limited land and energy resources more prudently. The case for denser cities seems obvious – but putting theory into practice will not be easy.
The Urban Land Institute has identified four common typologies of world cities according to density at the metropolitan, city (urban core) and neighbourhood level. These are:
Atlanta, Melbourne, Dresden, Nashville - Many North American and Australasian cities are the classic example of low-density urban areas. They have expansive suburbs, high levels of car dependence and spacious downtown zones.
Toronto, Oslo, Hamburg, Chicago - These are cities that have made conscious efforts to densify certain neighbourhoods or districts, while retaining a low-density urban area overall.
Paris, Vienna, Freiburg, Montreal - Many European cities fit this typology. They are characterised by high-density cores, but much lower-density suburbs, which significantly reduces the density of the overall metropolitan area.
Seoul, Shanghai, Tokyo, Mumbai - The pace of growth in many developing cities means they often fall into this typology. They are both sprawling and dense, with crowded informal housing on the peripheries and pockets of very high density, particularly around transit hubs.
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