SAINT JOHN – Many characteristics affect the look and feel of urban neighbourhoods. Two very important characteristics are building height and density. They can be related, but people often speak as if tall buildings and high density are the same thing. So what’s the difference?
Height is easy: a building is so many stories or so many feet tall. People easily understand how big a 16 storey building is. Density – the number of people or housing units in a given area – pardon the pun, is less concrete.
A common measure of density is units per hectare. Many people can’t picture a hectare, and the number of units in a 16 storey building isn’t always obvious. In addition, unlike height, many factors affect density: how much of the lot is built on, how tall the building is, how big the units in the building are, and how the units are layed out within the building. It’s hard to look at a building and know if it takes up 20% of its lot or 40%.
So with that in mind, here’s a simple question: which of the buildings pictured below is higher density?
If you guessed the high-rise, you’re right, but it’s a trick question. The two buildings have nearly the same density. The low-rise building, in Uptown Saint John, takes up most of its 1400 square metre lot. It has twenty units, on 0.14 hectares, for a density of 142 units/ hectare. The high-rise is in suburban Saint John, and the building’s footprint takes up a very small portion of its 8800 square metre lot. It has 129 units, on 0.88 hectares, for a density of 146 units /hectare.
Don’t worry if you fell for my trick question. A lot of people make the same mistake, including Harvard professor Edward Glaeser, who suggests in this article that the low rise, extreme density Mumbai ward, Dharavi, is in fact low density.
Why is this so important? Density is one of the most important characterisitcs of urban areas. High densities are important in creating vibrant streets, supporting main street commercial areas, and encouraging walking and transit ridership. Building at higher densities allows more people to live near workplaces, shops, parks and school. Increasing density is a common goal for cities that want to revitalize downtown neighbourhoods. Developers also like to build dense developments since they can be very profitable, especially when land prices are high. Unfortunately, density is often confused with height, making it difficult to have a conversation about what type of development is right for different cities and neighbourhoods.
Photos by Sean Gillis and Bill Lapp