What is FSI (Floor Space Index) or FAR – Complete Information

We all come across FSI or Floor Space Index but many of us hardly know what it means. FSI is also referred to as FAR that is Floor Area Ratio. Read this for full post to understand the basic concept of FSI or FAR.

The construction industry has always been demanding hike in FSI, so that they can construct higher buildings and earn more profits. A higher value of FSI or Floor Area Ratio is also an indicator of the development and progress of that particular area.

FSI in simple terms is the permissible area available to construct house or building in your plot. Total plot area can not be used to construct, thus suitable value of land should be left in order to have air circulation and other important functions for any building.

What is Floor Space Index

Floor Space Index is given by the ratio of the total constructed area to the total land area on which construction is to be done. Note that total constructed area exclude certain area like exterior spaces, parking area, patios, balconies, etc.

You can find the list of area included and excluded in FSI from the list given below.

FSI in mathematical form is given by,

FSI = Total built up Area/ Total Plot Area

Built-Up Area in FSI

Total built-up are include only usable space in a building excluding certain area.

The list of area included in FSI and excluded are given below.

Other Terminology Used for FSI

Floor Space Index as said earlier is commonly referred to as Floor Area Ratio (FAR) but there are many other names which are interchangeably used. FSI is also referred to as Floor Space Ratio (As it is the ratio of spaces), Gross Plot Area (GPA) Site Ratio or Plot Ratio.

Scroll down or click to Read the list of countries and commonly used term for FSI.

Difference between FSI or FAR

Even though FSI and FAR are interchangeably used but they are not the same. The most prominent difference is the value of both of them.

From the naming convention it is clear that FSI is an Index value, whereas FAR is a ratio. As we know that index is represented as percentage of base figure. While ratio is division of two numbers.

For example,

Assume Plot area of 100 m², and permissible area to be constructed is 150 m².

Therefore FAR = Gross floor area/Total plot area

FAR = 150/100 = 1.5

FSI will be represented as a percentage and will be equal to 150%

Thus FSI = 150%

FSI in Parts of India

Depending upon the locality, plot size and road width FSI / FAR value can vary from place to place. Different city in India has different FSI value. The table shown below give the minimum and maximum value of FSI in a particular state are listed below.

FSI value shown below can vary from place to place according to the local municipality and authorities. Generally, redevelopment projects have higher FSI value.

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Factors Affecting FSI Value

FSI plays an important role for the development of an area. Higher or lower FSI value impacts the construction activity in a place.

The following are the main factors that affect the FSI value of any place.

• The locality of the plot whether it is in a rural or urban area.
• Width of the road adjoining the plot or property.
• Type of building or purpose of the project for example residential building, commercial building or industrial building.
• Availability of water, electricity, and sewer lines.
• Types of building also affect the FSI values:
  • Normal ordinary (maximum of two floors)
  • Special building (Minimum two floors and maximum 4 floors)
  • Multi-storied building (more than 4 floors)

Why is FSI important

FSI is used to indicate the density of construction in a given region. A higher value of FSI in a region indicates a denser construction.

Local municipal government’s appropriate authority regulates the value of FSI based on various factors like population density, open space availability, environmental impact and resiliency to a natural calamity.

After carefully analyzing all factors local government allows FSI accordingly. Based on the FSI the builder constructs the building abiding by the building bye-laws.

Higher FSI means the builder or developer takes more interest as they would be able to construct more and sell more. And if a lower FSI is allotted then lesser construction is allowed on the given plot.

Importance of FSI

• FSI helps in maintaining a balance between open space and built-up space.
• It helps in maintaining the city skyline.
• It helps in maintaining Sustainable and planned growth.
• FSI impacts the value of land.
• FSI helps the government to decide and plan the percentage of park and open space area.
• FSI controls unnecessary construction.
• FSI controls the vertical growth and living situation in metro cities.
• It keeps a check on the density of cities by controlling construction.
• It ensures a clear horizon for the area.
• Higher FSI value promotes better development of the area.

FAR or FSI practical example

Suppose in a particular area based on the density of the population and other factors a municipality gives FSI of 2. That means a developer or builder can construct area of two times that of the land area.

Suppose that developer wants to develop a property on a land of 100 m².

As FSI is 2, the total usable floor area that can be constructed on a plot of 100 m² is

Total usable floor area = 100 x 2 = 200 m²

The builder can construct 200 m² of floor area on a land of 100 m² by constructing multiple floor on building.

One thing to note here is that this 200 m² of floor area is only usable are excluding parking, balconies, garden, and other setback areas.

Suppose that 50m² of area is used in parking and other areas that are excluded from the window of FSI.

That means total area the builder will construct can be 250 m² but only 200 m² of area can be used by inhabitants.

The builder can construct building on 50 m² of plot area and leave 50 m² of plot for ventilation an air circulation. Four storey building of 50 m² area constructed on each floor will amount to 200 m² of floor area excluding certain area that are not accounted in FSI.

Floor area on each floor = 50 m²

4 storey building, Total area = 50 x 4 =200 m²

Thus if FSI changes to 3, the built up area will be 100 X 3 = 300 m².

Purpose of Floor Space Index

Every government want to have a control on the population of an area so that it can effectively provide basic amenities to its citizens. FSI is one of the tool to divide the land into appropriate zones to restrict density.

Local municipality gives FSI accordingly to control the population of a particular zone. If local government want to decrease density of a zone it can curtail or decrease the FSI so that less construction is done on a given plot.

For example, if FSI of an area is 0.5 then only half of the plot area can be constructed. Hence if 10,000 sqft of plot is to be constructed then only half of it can be constructed, which comes to be 5,000 sqft.

Accordingly, architects can plan to construct a single floor of 5000 sqft or 5-storey building of 1,000 sqft each. But in no case, it can surpass the value of the permissible area of 5,000 sqft.

Impact of Floor Space Index (FSI) on Property prices

As said earlier higher FSI indicates development and growth of a region. Thus FSI indices influence the price of a property.

Higher FSI means a developer can build greater flats and thus sell more unit of houses that will finally be sold for greater profits. If FSI values increase in a region then the Property prices also increase considerably. Read more about Floor Area Ratio here.

How is FSI referred to in other countries?

Although the basic function of FSI is to measure the density of construction in a particular area. But different countries are using different terms which you can find in the below table.

What is Premium FSI

The floor space index of a building can be extended more than the permissible FSI under certain conditions. But to extend the FSI you need to pay a premium fee to the government in order to avail of extra FSI.

Extra FSI is allowed only if the adjoining road that leads to the building or property is wider than 30 feet. If your access road is wider than 30 ft then by paying a premium fee to the government you are allowed to construct a larger floor area then that is permissible.

Premium FSI Calculation

Premium FSI is calculated above the normal FSI. The calculation of premium FSI can be understood by the example shown below.

Example 1

Suppose a plot of 1000 sqft on a 50 ft road and FSI available for construction is 2 FAR. With FSI of 2 one can build twice of the plot area which is 2000 sqft. But as the plot is available on a 50 ft road than a premium FSI of 30% is also available to avail by paying premium FSI fees.

30% premium FSI of 2000 sqft accounts to 600 sqft. Thus total carpet area that can be constructed on a plot of 1000 sqft is 2600 sqft.

Plot size = 1000 sqft
FSI = 2
Built Up Area = 2 X 1000 = 2000 sqft

Premium FSI = 30% (as the plot is available on 40 -60 ft road)

Extra Built up area = 30% of 2000 sqft = 600 sqft

Total Built Up Area = 2000 + 600 = 2600 sqft

Example 2

Suppose a plot of 5000 sqft on a 60 ft road and FSI available for construction is 3 FAR. With FSI of 3 one can build thrice of the plot area which is 15000 sqft. But as the plot is available on a 60 ft road than a premium FSI of 40% is also available to avail by paying premium FSI fees.

40% premium FSI of 15000 sqft accounts for 6000 sqft. Thus total carpet area that can be constructed on a plot of 5000 sqft is 21000 sqft.

Plot size = 5000 sqft
FSI = 3
Built Up Area = 3 X 5000 = 15000 sqft

Premium FSI = 40% (as the plot is available over 60 ft road)

Extra Built up area = 40% of 15000 sqft = 6000 sqft

Total Built Up Area = 15000 + 6000 = 21000 sqft

What is TDR in Construction? How to Get Extra FSI

TDR stands for Transferable Development Rights. It is another way to obtain additional FSI other than premium FSI. It is a mean by which developer can build over and above the permissible floor space index (FSI) allowed in that location.

Government undertakes land from individual owners of land for infrastructural development and other reasons. The rate at which government purchase land is usually lowered than the market rate. Thus to compensate the land owner government provides TDR certificates that the owner can trade in the market.

TDR certificates are traded just like the stock market shares for cash. TDR trading is a huge market for developers to build extra and earn money. TDR is transferred from fully developed zones to the suburban areas so that the latter can also be developed.

Types of TDR in Construction

Basically, there are 4 types of TDR, which are mentioned below:

1. Road TDR,
2. Reserved plots TDR,
3. Slum TDR and
4. Heritage TDR

In major cities construction FSI is increased with the aid of TDR based on slum TDR. TDR certificates are used to build more in the urban areas and thus leading to intense pressure on infrastructure.

Frequently Asked Questions (FAQ’s)

Some of the most frequently asked questions about Floor Space Index are given below: