Anyone interested in the development of towns and cities has probably come across the concept of density. You might be an architect, planner, developer or landowner, maybe you are someone that works for government or, as most of us are, a resident that cares about their neighbourhood. In any case, you probably have an image in your head of the kind of place that you would like to live in and some idea of whether that is low, medium or high density. But is measuring density actually as straightforward as we assume it is? Key documents would suggest so.
Internationally the United Nation’s New Urban Agenda states:
“We commit ourselves to promoting the development of urban spatial frameworks, including urban planning and design instruments that support sustainable management and use of natural resources and land, appropriate compactness and density, polycentrism and mixed uses, through infill or planned urban extension strategies, as applicable, to trigger economies of scale and agglomeration, strengthen food system planning and enhance resource efficiency, urban resilience and environmental sustainability.” 1
The United Kingdom’s National Planning Policy Framework (NPPF) makes multiple references to density. This example is from chapter 11, “Making effective use of land”, in a section called “Achieving Appropriate Densities”:
“Where there is an existing or anticipated shortage of land for meeting identified housing needs, it is especially important that planning policies and decisions avoid homes being built at low densities, and ensure that developments make optimal use of the potential of each site.” 2
But what is an ‘appropriate density’, what is a ‘low density’? Both of these documents discuss density as if it is an entirely unambiguous concept. Neither document makes any attempt to define it. The word ‘density’ doesn’t even appear in the NPPF’s Glossary.
At one level of course, density is straightforward. You count or measure something and divide it by the area of land that it occupies. For example, to calculate residential density you count the number of homes and divide that by the area of the land that they sit on. Thirty houses on two hectares of land? Fifteen dwellings per hectare (15 d/ha). Sixty houses on two hectares of land? Thirty dwellings per hectare (30 d/ha.). Double the quantity of houses, double the density. However, there is an important caveat to this:
An architect whose work I admire wrote a piece titled “Density is just a number. What counts is quality of place”.3 It is an excellent article, there is however one key issue that needs to be addressed. Density is not just a number - density is a ratio. It is equally affected by the things counted or measured as it is by the area that they are counted or measured against.
What I aim to do in this series of blog posts is to investigate the impact of this singular issue on planning and urban design and to illustrate why density is not the simple measure that we often assume it is. The very way we measure it impacts the urban environments that we end up creating. The focus will largely be on London and the UK but comparisons will be made with other cities and countries where appropriate.
Footnotes
- United Nations Conference on Housing and Sustainable Urban Development (Habitat III). (2017). Resolution 71/256: New Urban Agenda. (23 December 2016). A/RES/71/256. Available from http://research.un.org/en/docs/ga/quick/regular/71 [Accessed 28 April 2020].
- Ministry of Housing, Communities and Local Government. (2019). National Planning Policy Framework. Available from https://www.gov.uk/government/publications/national-planning-policy-framework–2 [Accessed 2 May 2020].
- Park, J. (2018). Density is just a number. What counts is quality of place. Building Design. Available from https://www.bdonline.co.uk/opinion/density-is-just-a-number-what-counts-is-quality-of-place/5091732.article [Accessed 2 May 2020].