What is FSI?

Floor Space Index (FSI), also known as Floor Area Ratio (FAR), is a crucial urban planning parameter that regulates the maximum permissible construction area on a given plot of land. As per the Tamil Nadu Combined Development and Building Rules, 2019, FSI is defined as the quotient obtained by dividing the total covered area (plinth) on all floors except the areas specifically exempted under these rules, by the Plot Area and is represented by this formula:

FSI = Total covered area (plinth) on all floors / Plot Area

This ratio determines how much floor area can be constructed on a plot. For instance, with an FSI of 2.0 on a 1,000 sq.ft plot, you can build up to 2,000 sq.ft of total floor area across all floors.

Current FSI Regulations in Tamil Nadu (2025)

Non-High Rise Buildings (Up to 18.30m height)

• Maximum FSI: 2.0
• Applicable throughout Tamil Nadu under the unified 2019 rules

High Rise Buildings (Above 18.30m height)

Maximum FSI varies by road width:

• 12m road width: FSI 2.0
• 15m road width: FSI 2.5
• 18m+ road width: FSI 3.25

Spaces Excluded from FSI and Coverage Computation

The following shall not be counted towards FSI and plot coverage computation:

On Terrace Level:

• In the terrace above the topmost storey, areas covered by staircase rooms and lift rooms and passages thereto, architectural features, elevated tanks (provided its height below the tank from the floor does not exceed 1.5 metres) and WC (with floor area not exceeding 10 sq.m).

Parking Areas:

• Staircase and lift rooms and passage thereto in the stilt parking floor or upper floors used for parking.
• Staircase and lift rooms and passage thereto in the basement floor or floors used for parking.
• Area of the basement floor or floors used for parking.
• Area of the stilt parking floor provided it is open on sides, and used for parking.

Service Areas:

• Servants or drivers' bathroom and water closet for each block in cases of Non High Rise Buildings and High Rise Buildings at ground floor or stilt parking floor.
• Watchman booth.
• Caretaker booth or room in ground floor or stilt parking floor.
• Area for water/sewage treatment plants (with TNPCB approval).
• Service ducts and utility areas.
• Balcony/service verandah (up to 5% of unit area).

Premium FSI: Additional Development Rights

Premium FSI allows developers to build beyond the normal FSI limits by paying additional charges:

Premium FSI Rates Based on Road Width:

Road Width	Premium FSI Allowed	Charges
18m and above	50% of normal FSI	50% of guideline value (Non-High Rise)
12m - 18m	40% of normal FSI	40% of guideline value (High Rise)
9m - 12m	30% of normal FSI	As per guideline value

Special Discount for Metro Corridors

Properties within 500 meters of Metro Rail corridors receive a 50% discount on Premium FSI charges, effectively paying only 25% of the guideline value for additional FSI.

Setback Requirements

For Non-High Rise Buildings:

Front Setback (Based on Road Width):

• Up to 9m road: 1.5m
• 9m-18m road: 3.0m
• 18m-30.5m road: 4.5m
• Above 30.5m road: 6.0m

Side and Rear Setbacks (Based on Building Height):

• Up to 7m height: 1.0m
• 7m-12m height: 1.5m
• 12m-16m height: 2.5m
• 16m-18.3m height: 3.0m

For High Rise Buildings:

• Minimum 7m setback all around for buildings up to 30m height
• Additional 1m setback for every 6m increase in height above 30m
• Maximum setback requirement: 20m

Areas of Special Character

Continuous Building Areas (CBA)

Buildings without side setback are permissible in a plot or site in continuous building areas set apart in the approved Master Plan or Detailed Development Plan or in the other areas as may be declared by the local body as CBA with the approval of the Directorate of Town and Country Planning or Government as the case may be from time to time. However in an approved layout area only in the plots classified for Continuous type of buildings it is permissible.

• Maximum FSI: 2.0
• Minimum 1m internal passage required

Economically Weaker Section Areas (EWS)

Areas declared as slum by Tamil Nadu Slum Clearance Board (TNSCB) are categorised as EWS areas for the purpose of these regulations. In addition it includes the areas developed as EWS plot in the Tamil Nadu Housing Board (TNHB) neighbourhood schemes, Sites and Services schemes, slum improvement schemes and approved layouts. For the purpose of application of these rules the Local body may declare areas as EWS Areas by council resolution and notify from time to time.

• Relaxed setback norms
• Maximum FSI: 2.0

Coastal Regulation Zone (CRZ) Area

Developments in these areas shall be regulated with reference to the CRZ classifications and the regulations notified by the Government of India from time to time under section 3 of the Environment (Protection) Act, 1986 (Central Act 29 of 1986).

Conservation Zones in the Heritage Towns

Government may notify Heritage Towns, a list of Heritage precincts there in with metes and bounds and conservation zones around such listed Heritage precincts. Any new construction of building or use of premises in the conservation zones shall conform to the special guidelines relating to height, use etc., prescribed and notified by the Government from time to time.

Transit Oriented Development Areas

(i) In order to encourage Transit sensitive activities and to allow densifications in any mass rapid transit system in the state, the Govt. may prescribe such regulations, including premium FSI at concession rates as may be necessary from time to time.
(ii) In case of Metro Rail Corridors, Existing and Proposed properties located within a distance of 500m measured from the centre line of the corridor, Premium FSI shall be charged at 50% of the normal Premium FSI rate.
(iii) Proposed FSI up to 2.5 along metro corridors.

Natural Hazard Prone Areas

(1) Areas likely to have (i) moderate to very high damage risk zone of earthquakes, or (ii) moderate to very high damage by cyclones, or (iii) significant flood flow or inundation, or (iv) landslides proneness or potential, or (v) tsunami proneness, or (vi) one or more of these hazards, have been declared as natural hazard prone areas.
(2) The areas prone to natural hazards will be notified by Government from time to time. Structural design and aspects of building construction in these areas shall take into the account of the special provisions contained in these rules for hazard prone area.

Aquifer Recharge Areas

Restricted development zones for Chennai's water security:

• Maximum FSI: 0.80
• Maximum coverage: 40%
• Special rain water harvesting requirements

Important Considerations

Road Width Requirements:

• Minimum 9m for buildings exceeding 16 dwellings
• Minimum 12m for conference halls, AC cinema theaters
• Minimum 15m for kalyana mandapams, exhibition halls
• Minimum 18m for star hotels, multiplexes, malls

Mandatory Requirements:

• Parking: As per Annexure-IV standards
• Rain Water Harvesting: Mandatory for all developments
• Sewage Treatment: STP for >50 units or >2500 sq.m commercial
• Display Board: Project details must be displayed on site

Calculating Your Buildable Area

Example Calculation:

• Plot Area: 2,400 sq.ft
• Applicable FSI: 2.0
• Basic buildable area: 2,400 × 2.0 = 4,800 sq.ft
• With 30% Premium FSI: 4,800 + (4,800 × 0.30) = 6,240 sq.ft

Note: Actual buildable area depends on setbacks, road width, and other site-specific factors.

Latest Updates (2025)

1. Unified Rules: The Tamil Nadu Combined Development and Building Rules, 2019 apply uniformly across the state
2. Metro Corridor Benefits: 50% discount on Premium FSI charges near metro lines
3. Proposed Changes: CMDA has proposed increasing FSI to 6.5 for certain commercial areas (pending approval)
4. Digital Integration: Online submission through the Tamil Nadu Single Window Portal

These regulations are essential for urban planning and ensuring safe, sustainable development while accounting for various socio-economic and environmental factors. The Tamil Nadu Combined Development and Building Rules, 2019 have streamlined the development process by consolidating all regulations into a single comprehensive document.

*Disclaimer:

The FSI information provided on this website is based on the Tamil Nadu Combined Development and Building Rules, 2019, and subsequent updates. The calculations and outputs are based on the regulations and guidelines available at the time of use. However, the accuracy and applicability of the results may vary depending on specific circumstances, updates to regulations, and interpretations by relevant authorities.

Users are advised to consult with qualified professionals and verify the results with local regulatory bodies (CMDA, DTCP, or local municipal corporation) before proceeding with any construction or development projects. Site-specific conditions, heritage regulations, and environmental restrictions may apply additional limitations. Verified.RealEstate and its developers do not guarantee the accuracy, completeness, or reliability of the information provided and shall not be held liable for any discrepancies, errors, or omissions in the results.

For official documentation and updates, please refer to the Chennai Metropolitan Development Authority (CMDA), Directorate of Town and Country Planning (DTCP), or your local municipal corporation.

By using this FSI information, you acknowledge and agree to use it at your own risk and discretion.