1.) Floor Area Ratio
Floor Area Ratio (FAR), in some countries also known as Floor Space Index (FSI) is the ratio between the sum of floor area and the size of the development plot. We can calculate it by simply dividing the total Gross Floor Area (GFA) of all buildings and the Plot Area. GFA includes private units and common areas and is assembled from the floor area, including the structure of the building. FAR is a number that is always positive, 0 means there are no buildings on plot.
FAR is key parameter that regulates density of the city. It is important in order to control the bulk of buildings and intensity of surrounding activities.
There is no good or bad FAR because the final design solution depends on different factors, such as the density of surrounding development, urban growth patterns, population dynamics, mix of uses, etc. Floor Area Ratio is among the most commonly used instruments of regulation by municipalities. It sets maximum or minimum development potential of a certain plot or area.
2.) Site coverage
Site Coverage tells us how much of the parcel or development area is built. We can calculate Site coverage by dividing Built-up Areas (building footprins) of all buildings of the plot with Plot Area. The result is relative number from 0 to 100%. For example, 20% Site Coverage would tell us that 20% of the site is covered by buildings.
Site coverage is used to make sure there is enough space for other areas, besides buildings on site, such as Green Areas. Usually, in the regulation process, the municipality declares that a particular plot can only cover up to n% with buildings and n% has to be green areas, etc.
3.) Green Area Ratio
Green areas are an important part of new developments. Quality, sustainable and livable cities can only be achieved if there are enough green areas, based on density, number of inhabitants, apartments and more.
The Green Area Ratio tells us what % of the plot should be green. It is calculated by dividing the Floor Area of the plot or parcel with the green areas. Green Area Ratio is different, depending on city regulations and land use of a certain area, as well as density. This ratio prevents serves as a guidance for a balanced ratio between build and non-build environment. It is a way for the city to make sure new developments work well for all citizens, even those with lower income.