CBD apartments, Brisbane (Source: wiki)

The pejorative term “vertical sprawl” is gaining currency in public discussion about cities. It’s been taken up with alacrity by those who oppose high-rise redevelopments in the centres of cities in Australia, Canada and the US.

It cleverly conflates distaste for suburban sprawl at the metropolitan fringe with aversion to high-rise infill development in the centre. If sprawl is obviously bad, so then are those high-rise residential towers in Brisbane, Sydney and Melbourne, right?

It might be a smart spin by critics of high-rise, but the idea of sprawl has little relevance to the sort of housing going up in the centre of Australian cities. There are important issues like over-shadowing, separation between towers, and the quality of ground level design associated with tall buildings, but the concerns related to suburban sprawl are quite different.

The downsides of sprawl are mostly a function of low density development. They relate to issues like displacing agriculture; destroying bushland; encouraging unsustainably large properties and houses (‘McMansions’); generating excessive car-based travel; breeding social isolation; and undermining social cohesion.

Towers however accommodate residents at very high densities. In Australian cities they’re almost always constructed in the inner city (especially in or close to the CBD) or in large suburban centres with good public transport access.

Consider a hypothetical high-rise building on the edge of the CBD housing 350 residents in 250 one and two bedroom apartments. It occupies a site of around 1,500 sq m with a street frontage of 40 metres (1).

The same number of residents in a sprawling fringe estate requires only 145 houses, but each one has a land area of around 550 sq m. That’s a total of 80,000 sq m (8 Hectares); plus kilometres of streets to provide direct access to each house.

The high-rise is much more sustainable. It’s mostly small 50 sq m one-bedroom and 75 sq m two-bedroom apartments so it’s easier to cool and can hold less “stuff”. Each apartment is insulated by its neighbours on two or three sides, as well as above and below.

Outer suburban houses are much larger. They each have an internal floor area upwards of 150 sq m, three to four bedrooms, and multiple living areas. Each one is completely detached from its neighbours.

High-rise residents live close enough to walk to many nearby services and facilities that cater to office workers and other apartment dwellers. They are only a short distance from the huge concentration of jobs in the CBD.

Since they live at the focal point of the public transport network, they’re able to access the entire metropolitan area without driving. Many fewer own cars compared to outer suburban households; that’s partly because there’s less point in having a car in the centre and partly because they’re expensive to park.

At the 2011 Census, 33.9% of workers living in the CBD-edge suburb of Southbank in Melbourne walked to work and 20.1% used public transport. Further, 27.9% of apartments had no motor vehicle (2).

Contrast that with the fringe suburb of Cranbourne East where less than 1% of commuters walked to work and 6% used public transport. Moreover, only 3.2% of houses had no motor vehicle.

Residents of high-rise have a mix of activities literally at their doorstep and ready access to many public and private venues where they can see and meet others. Most developments have common facilities and even those who drive see other residents in the elevator.

Of course tall residential buildings present a range of design issues. They include privacy (e.g. distance between neighbouring towers) and access to light, as well as overshadowing and wind effects at ground level.

But these are problems of how to manage large numbers of people living in a very small area. They’re problems of high density, not sprawl. What matters most for high-rise living is how well the building functions at ground level e.g. street activation and access to services and facilities.

The term “vertical sprawl” might make more sense if it were reserved solely for isolated residential towers in a suburban setting with poor infrastructure. In our cities, though, residential high-rise is almost always confined to the inner city or suburban activity centres (3).

Coincidentally, John Watson writes this morning on how a culture of hysteria hijacks our language. It’s worse than that: public debate has been “tea-partied”. Truth and plausibility seem to have been abandoned in the rush for the trenches of partisanship (see also Infrastructure: does getting the facts right matter anymore?).

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  1. There’re plenty of much denser developments. When completed, Melbourne Tower will have almost 600 apartments on 913 sq m.
  2. For Victoria, 3.3% of commuters walk to work and 9.4% take public transport. 8.4% of dwellings don’t have a motor vehicle.
  3. It would still be an imperfect analogy even for a tower located outside an activity centre, because any time very large numbers of people live in a very small area it’s bound to create some demand for local services and generate more interaction between residents than standard suburbia.