Getting the Density Right

Density is the most useful urban design tool and yet the least understood measurement in residential masterplanning. Getting it right is essential because getting it wrong can spell disaster.


Funnily enough we still measure in hectares and well as acres, metres as well as feet, inches as well as millimetres. We also measure density as gross and net. We measure density as units (houses) per hectare and units per acre. We also measure density as the number of habitable rooms per hectare or acre. That adds up to six different ways of measuring density. There is also another, less widely used way, and that is inhabitants per hectare or acre.


So even before we start to discuss density, there is confusion!


During my twenty years in the residential development industry I have observed, with relentless frequency, the same mistake being made over and over again. That is working our how many units can built on a given site by measuring the GROSS site area and applying a density to generate a number of units per hectare – or acre.


This does not work.


The density must be applied to the NET site area only. Now herein lies the problem. How can you determine the net area when you have no details about the constraints and you have no layout? It is perfectly reasonable to assume that you would not have this information when considering a site for development and it is fair to assume that you do not want to spend any money on architects or masterplanning fees. So you need to have a ‘rule of thumb’ for establishing the % difference between a gross and net site area.


In addition you need to know what various densities will look like and what density will trigger the need for apartments. You should be interested in the density of the surrounding areas so that your proposed development will fit into the urban grain appropriately. You need to know how the unit mix will affect the density and whether wide fronted houses take up more space than narrow fronted houses over the whole site.


Fortunately we have worked on over fifty residential developments and have all the necessary data to create some ‘rule of thumb’ calculations, backed up by real examples, you can use to understand and determine density and ensure there are no surprises down the line.


All you need to do is keep a look out for:


The Bluepencil Designs DENSITY MANUAL which will be available soon!

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