All You Need To Know About Floor Space Index (FSI)

by Dynamix Group Writer

Also known as Floor Area Ratio, Floor Space Index is the ratio of the total floor area covered in a building to the total area of the plot on which the building is built. It helps to determine the total amount of area that can be built upon a plot. To calculate FSI, simply divide the total constructed area with the total land area. (FSI = total constructed area/ total land area)

In other words, if the authorities of a city set the FSI to 2 in a particular area, one can build a coverage area of 4,000 sq. ft. on a 2,000 sq. ft. plot. The FSI limit is not the same for all the cities. Depending on the development strategies of the authorities, it differs from city to city.

The Significance of FSI

According to Shahid Balwa of DB Realty, with the booming population in India, it is quite difficult to accommodate every resident without a meticulously designed strategy. Space is a limited resource, especially in metro cities. This calls for a strategy that can accommodate more people but occupy lesser space. Hence, the idea of vertical growth came into practice. Taller buildings in a city not only offer an aerial view of the city but allow more people to accommodate as well. As the population is growing at an alarming rate in the cities, vertical construction is one of the many paramount strategies of urban planning. Depending on the needs, the development authorities in cities set the Floor Area Ratio (FAR), or Floor Space Index (FSI).

Factors affecting FSI norms

Shahid Balwa says FSI is not always fixed. There are many factors that affect the FSI norms like:

• Transfer Development Rights (TDR)

• Additional FSI

• Premium FSI

• Transit Oriented Development (TOD) influence zones

• Redevelopment projects

Recent TN amendment

On October 26, a few amendments were added to the Second Master Plan for CMA, 2026:

• Ordinary building, special building, group development and multi-storey buildings are the only categories under residential developments where FSI is applicable.

• In Tamil Nadu, the uniform FSI increased to 2 FSI from 1.5 FSI earlier for residential developments.

• The residential plots with the minimum extent of 1,500 sq.m. and minimum road width of 18m are allowed FSI of up to 3.25.

• Premium FSI of 40%, 30% and 20% which was earlier for road widths of 18m and above, 12m to below 18m and 9m to below 12m have increased to 50%, 40% and 30% respectively.

• FSI for non-residential/other developments has remained the same.