FSI (Floor Space Index)
last updated 2026-07-21
Floor Space Index (FSI), also called Floor Area Ratio (FAR), is the ratio of total buildable floor area to plot area. In Tamil Nadu, non-high-rise buildings up to 18.3 m are generally allowed an FSI of about 2 — so a 2,400 sq ft plot permits roughly 4,800 sq ft of construction, subject to setbacks.
What FSI means
FSI (or FAR) is the total covered floor area you may build across all floors, divided by the plot area. An FSI of 2 on a 2,400 sq ft plot allows about 4,800 sq ft of floor space in total. It is set by the development rules and is the single number that caps how much building a plot can carry.
The Tamil Nadu position
For ordinary non-high-rise buildings (up to about 18.3 m in height), Tamil Nadu generally permits an FSI of around 2 under the Tamil Nadu Combined Development and Building Rules, administered by CMDA in the Chennai metropolitan area and by DTCP elsewhere. The exact permissible FSI varies with the building type, road width and zone, so treat 2 as a common benchmark, not a universal figure.
Why it affects value
Two plots of the same size can be worth different amounts if their permissible FSI differs — more FSI means more saleable floor area, which is why FSI feeds directly into what a plot is worth to a builder. And the headline FSI is only achievable after leaving the required setbacks, so the usable build is always a little less than the raw number suggests.
The bank-auction angle
For a plot or a redevelopment-minded purchase at auction, the permissible FSI shapes what you could do with it — and therefore what it is worth. It is not stated in the sale notice, so it is a check to run against the local rules for that zone. AuctionScope helps you weigh a listing's price and location; confirm the buildable potential with the planning authority. This is general information, not professional advice.
Frequently asked questions
What is FSI or FAR?
Floor Space Index (FSI), also called Floor Area Ratio (FAR), is the total buildable floor area divided by the plot area. An FSI of 2 means you can build twice the plot area in total floor space.
What is the FSI limit in Tamil Nadu?
For non-high-rise buildings up to about 18.3 m, Tamil Nadu generally allows an FSI of around 2, under the Combined Development and Building Rules. The exact figure varies with building type, road width and zone.
Why does FSI matter when buying a plot?
Because it caps how much can be built, and therefore what the plot is worth to develop. More permissible FSI means more saleable floor area — though the required setbacks mean you rarely build the full headline figure.
Related terms
Sources
Rates, fees and procedures change — confirm the current position on the official portals below before you act.