Density
The layout and density of urban districts are two of the most important parameters to consider in the early design
phase. The density of the urban fabric is expressed by the Floor Space Index (FSI), Plot Ratio or Floor Area Ratio
(called FSI in the rest of this article). Formerly defined, the FSI is the ratio of a building's total floor area in relation
to the size of the plot on which it is built, see Figure 1. A plot with no buildings on it has a FSI of 0. Building the
same amount of floor area as the plot area results in a FSI of 1; two floor slabs covering the entire plot results in
FSI=2 etc. The same FSI can thus be reached by adjusting the ground floor area and the amount of floors in a
building, as shown in Figure 1. Also, a site with a large unoccupied space and a high FSI will results in tall
buildings. Table 1 shows the FSI of different cities. Note that in some cases, the maximum allowed FSI is per plot,
and that the FSI is only per building plot, not including streets, which explains why some cities are known to be very
spread (like e.g. San Francisco compared to Amsterdam or Paris). Note that is difficult to provide an overview of
FSI of cities in the world due to differences in calculation methods.