What is floor space index also known as FSI in construction work


Royal Member
Floor Space Index (FSI), also known as Floor Area Ratio (FAR), is the ratio of total floor area of a building (Built up area) with reference to the total Plot area (land). This numeric value indicates the total amount of area (on all floors) a building can be constructed on a plot.

How to derive the FSI for Building?
FSI regulates by Development control regulation authorities of a concerned municipal corporation , town planning department etc in line with the National Building Code of India.
They will regulate the FSI value based on city zone,( as defined as development control rules) type of building and other amenities. Construction can be done only on the basis of FSI.

Example for FSI Calculation:
Let us assume assume that you have a land of 10000 sq.ft and a building has to be constructed on that land.
First t, you have to know is what type of building you are going planning to construct.is it a Residential Building or a Commercial Building.
Classification according to the no. of floors, type of the building ( Institute, Healthcare, Hospitality)
based on your building type, one can find out the FSI. Normally different buildings have different FSI regardless of the location. For the same location, FSI can vary on the no. of floors of the building.

As per thane municipal the FSI is 1.5 for a building.
10000 x 1.5 = 15000 Sq.ft of floor covered area can be constructed on this land.
It can be either be 3 floors of 5000 Sq.ft or 2 floors of 7500 Sq.ft without affecting other municipal rules (Minimum plot extent area, setback, parking space etc).
Apart from the regular FSI premium FSI also available. Let me explain What is Premium F.S.I?
There are some allowable deviations, regardless of location and building type.

If you need to extend the allowable Floor Space Index (FSI), you have to pay a premium fee to the govt. To avail this FSI, the abutting road of the land must be at least 30 feet.

If the land location of the building has 30 – 40 feet next to a roadway, then you can make avail the premium FSI of 20% which means you can build 20% more than allowable FSI. Similarly, for 40 – 60 Feet Road Width – 30 % Premium FSI and more than 60 Feet Road Width – 40 % Premium FSI.( refer the concern d.c.rules of the municipal corporation)

Advantages :
FSI may be considered as a restriction but it has his own benefits in a city or a place where construction is progressing in a huge speed.It maintains the ratio of open space to built space.

It maintains the skyline line of the city A average FSI value ensures a good development of the project.

Hence, with average FSI one must turn it into an asset and design the end product that caters and solves all the requirement of the project.