Urban density matters – but what does it actually mean?

Shove up: London's Oxford Street, looking crowded. Image: Getty.

In debates about urban density we often find comments about buildings being too tall or not tall enough, about too many people in a neighbourhood or too few, about streets and buildings being overcrowded or empty.

We are told that Melbourne is building at four times the density of Hong Kong, or that density is good and will make us happy.

But as these debates over density in cities continue, what is most often missing is any clear understanding of what people mean when they use the word “density”.

Is it the volume or height of buildings? Or is it the numbers of people? One person’s high density may be another’s sprawl; the same tall building may be experienced as oppressive or exhilarating; a “good crowd” for one can be “overcrowded” for another. One is reminded of Humpty Dumpty’s logic in Through the Looking Glass:

When I use a word it means just what I choose it to mean – neither more nor less.

What such debate most needs is greater density literacy.

Density is a concept borrowed from physics where the meaning is clear – mass divided by volume. Yet when transferred to the city, nothing is so simple.

Are we talking about buildings or people?

First, we need to clarify whether we are talking about concentrations of people or of buildings. If we take population densities first, these are generally measured as residents per hectare based on census data.

But we also need to distinguish between “internal” and “external” densities – the numbers of people in a room or apartment versus those in an urban precinct. If you look at new high-rise housing in the evening, you can find many apartments unoccupied. At the other extreme, internal crowding largely defines a slum. Building density does not mean population density.

Building density does not necessarily mean population density, an example being low-occupancy housing in Melbourne Docklands. Image: Kim Dovey/author provided.

Population densities cannot be based on residents alone, since the numbers of people in a given neighbourhood at a given time include those who work there or are visiting. In a mixed-use neighbourhood, residents may be a small proportion of the population density.

There are also population density rhythms, as people move from place to place throughout the day and week. The same urban precinct can be densely populated during work hours and empty on weekends. Population density is not only the number of residents but fluctuates over time and with functional mix.

And how do you measure building density?

When we shift attention to building densities, we soon encounter some unavoidable jargon. The most common measure of building density is the “floor area ratio” (known variously as FAR, FSI, FSR and plot ratio) – the ratio of floor area to land area. This is the most widely used measure for limiting the bulk of development on any given plot.

However, it does not control the building height, “footprint” (the area occupied by the building) or “coverage” (the proportion of land covered by buildings). Thus it is quite possible to build high-rise low-density (with very low coverage or small footprints) or low-rise high-density (with high coverage or large footprints).

Most high-rise public housing from the 1960s and 70s is roughly the same FAR as the low-rise housing that was demolished to build it.

Building height is not a measure of density, although sometimes the two align. Confusions here abound; press reports (such as here and here) regularly equate FAR with height control.

Areas of different heights but similar building density in Fitzroy, Melbourne. Image: Kim Dovey/Google Earth.

Another common measure of density is dwellings per hectare. This is often used as a means of assessing population and building densities at the same time. But it does neither, unless we know the size of dwellings and of households. Thus dwellings per hectare is a very blunt measure of density, although a useful proxy for comparing housing projects.

Then there is the distinction between gross and net densities. Urban planning controls are focused on the net density on a particular site – yet such measures are of little use in understanding how cities work, because they do not include the public space of streets and parks.

The gross density is always lower than net density and it is the one that matters in debates over urban density. While we might be packed in on a particular site, the street network of a car-based city tends to keep us apart. Net density is not an effective measure of urban density.

As we measure densities of people or buildings at larger scales, we also incorporate water bodies, freeways and unbuildable sites, so the average density diminishes. Where one draws the boundary is a crucial decision in measuring urban density, or in getting the answer one wants.

Even urbanists such as Paul Mees can be guilty of this when using broad metropolitan density measures to advocate for public transport at suburban densities. Elizabeth Farrelly, a vocal proponent of higher density, compares it to the thread-count of luxury sheets (her minimum is 1,000), yet her only measure for urban density is “dwellings per hectare” – whatever the scale, net or gross.

Here we encounter the politics of density literacy and return to the logic of Humpty Dumpty:

The question is which is to be master – that’s all.

There is no single scale at which to measure urban density, but the larger the scale, the lower the density. The best approach is to understand density as multi-scalar: for any location there is an internal density, a net density, a walkable density and a metropolitan density.

High density is no guarantee of urban buzz

Finally, there is the question of streetlife density – of people in public space, of crowds and crowding. Here the complexities multiply. While we can measure the outcomes in pedestrians per minute or per square metre, we are far from understanding the ways in which streetlife is geared to building and population densities.

These connections depend at least on numbers of jobs and visitors, functional mix, car dependency, access networks and walkability. Yet this is where density delivers its greatest benefits in social and economic encounters – what we often call the urban “buzz” or “intensity” – along with disbenefits such as congestion.

Density without intensity in the car-dependent city – in this case, Tampa, Florida. Image: Author provided.

In Australian cities we have become quite good at generating high density without intensity. Think of car-dominated high-rise districts where few people use the street. Yet we also have good inner-city examples of intensity without high density.

For many people, density has become a negative word. Those who want more of it often use other words and phrases: the “compact city”, “urban intensification”, “transit-oriented development” and the “30-minute city”.

This can be useful language but the question of what it means remains. The challenge is to raise the standard of urban density literacy – not to make density mean one thing but, as Alice might put it, to understand the ways it is made to mean so many different things.The Conversation

Kim Dovey is professor of architecture and urban design, and Elek Pafka a research fellow, at the University of Melbourne.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

Transport for London has banned short term letting ads

STILL no idea. Image: Generation Rent.

Back in June, Generation Rent won a moral victory. After 8,000 londoners signed an online petition, we were able to force short terms lets company Hostmaker to pull down their offensive adverts, which encouraged landlords to kick out their tenants.

But it wasn’t just Hostmaker that was at it. Rival firm Nestify launched a campaign of disgusting adverts, which used almost the exact same messaging and data analysis as Hostmaker to send the same message: landlords, ditch your tenants. It felt like where one dodgy ad was defeated, another popped its ugly head to replace it.

But this week we’ve got cause to celebrate again. Behind the scenes, we’ve been working on going one step further – and now Transport for London has announced brand new guidelines banning all short term let adverts. 

The new policy, which can be found here, states that any adverts seen to do the following would be banned from the network:

  • imply that removing properties from the private rental market for other rental purposes, such as short term lets to tourists, can be financially or materially advantageous to property owners;
  • promote companies or services which appear to rely on property owners removing their properties from the private rented sector; 
  • appear to conflate short term lets with lettings in the private rented sector – the type of lettings the advert is promoting should be unambiguous;
  • advertise services for both types of lettings;
  • Use phrases or terms associated with short term lets where they are ostensibly advertising services relating to lettings in the private rented sector, or vice versa.

So what’s the problem with short term let advertising? Well, besides the obvious incitement to evict your tenants to make more money, the short term let industry has been notoriously hard to regulate in large cities like London. Whilst the capital has a ban on renting out your home for holiday lets longer than 90 days, Hostmaker was caught out in February deliberately trying to break the 90 day limit on short term lets. And in a city like London with sky high rents and more people than ever living in cramped house shares, it’s crucial that long term homes are available for all.

It feels nice to be right…

Georgie Laming is a campaigner at Generation Rent, which represents 11 millions renters across the UK.