Due to the sheer number of construction and development projects being carried out simultaneously, often the deciding factor for the question “Which project is better?” is dependent on whether these projects meet Chennai Metropolitan Development Authority (CMDA) guidelines. Though the CMDA guidelines for developmental projects are quite extensive, let us look into one of the most important highlights that buildings should meet in order to receive CMDA approval.
The rules laid down by the CMDA divide buildings into three types, ordinary buildings, special buildings and multi-storeyed buildings. This classification is based on the height of the buildings, number of households in a plot and extent of commercial activity. The ‘ordinary’ buildings are the buildings that do not exceed a height of 9 m (30’) in height. These are generally low ground plus one-storeyed building. The ‘special buildings’ cannot exceed a height of 15 m (50’). These are generally residential or commercial buildings with more than two floors. The ‘special buildings’ are, as the name suggests, a special type of multi-storeyed buildings. These consist of residential buildings with more than four dwelling units and commercial buildings exceeding 300 meter square (3228 sq. ft.) of plinth area. When it comes to these buildings, the height of 15 m matters more than the use to which they are put, be it residential or commercial.
However, most of the buildings, nowadays, fall under the ‘special category’ section and hence, this is the topic we will take forward here.
The Floor Space Index (FSI), also known as Floor Area Ratio (FAR), Floor Space Ratio (FSR) and Plot Ratio, is the index by which the total constructible area can be calculated. This index is used by the authorities to control the density of development.
Constructible area = Land Area * FSI Index
The FSI for ordinary and special buildings (residential and commercial) is 1.5. This means that the plinth area should not exceed 1.5 times the area of the plot where construction is being projected. If the area of the plot where the construction is proposed is 9600 sq.ft, with a 1.5 FSI, the total plinth area is 14,400 sq.ft. However, there are a few exemptions to the this calculation like parking area, electrical transformer room, garbage area, caretaker's room, etc., provided the plinth area of such service areas does not exceed 10% of the total plinth area. Staircase headroom and the lift machine room in the topmost floor are also excluded from this calculation.
FSI can be availed on all plots that abut on a road that has a minimum width of 30 feet. The premium FSI for plots that meet roads that have a width of 30 feet or more and lesser than 40 feet is 20% of the normal FSI. The buildings on plots that abut roads that have a width more than 40 feet and lesser than 60 feet, have a premium FSI of 30% and the plots that abut a road with a width of 60 feet or more have a premium FSI of 40%. However, premium FSIs are allowed for specific regions only and are also accompanied by additional premium fees.
To find out more about Floor Space Index (FSI) in Chennai, visit "Floor Space Index"
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