These Rules categories buildings as High Rise and Non-High-Rise buildings. Buildings with height up to 18.30 Meters are Non-High-Rise Buildings. For these Non-High-Rise Buildings, the maximum Floor Space Index or FSI allowed is 2

The Tamil Nadu Government has Notified the new Development and Building Rules, in 2019. It is applicable for the whole of Tamil Nadu. It’s known as Tamilnadu Combined Development and Building Rules, 2019. 

The floor space index, also known as FSI, helps us calculate the maximum floor area that one can construct in a Plot. 

Definition of FSI 

FSI is one of the tools under the Rules with which the Government regulates the construction activity. 

In the Rules the FSI is defined as under: 

FSI is the quotient obtained by dividing the total covered area (plinth) on all floors except the areas exempted under these regulations by the plot area which includes part of the site used as exclusive passage. 

What Are the Exemptions from FSI Norms? 

The exempted areas are also given in the Rules. According to the Rules, the following shall not be counted towards FSI and plot coverage computation:  

1. In the terrace above the top most Storey, areas covered by stair-case 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 meter) and WC (with floor area not exceeding 10 sq.m) 

2. Staircase and lift rooms and passage thereto in the stilt parking floor or upper floors used for parking 

3. Staircase and lift rooms and passage thereto in the basement floor or floors used for parking. 

4. Area of the basement floor or floors used for parking 

5. Area of the stilt parking floor provided it is open on sides, and used for parking. In cases where upper floor or floors over a stilt parking floor is proposed for parking. 

6. Servants or drivers bath room and water closet for each block in cases of Non-High-Rise Buildings and High-Rise Buildings at ground floor or stilt parking floor 

7. Watchman booth 

8. Caretaker booth or room in ground floor or stilt parking floor 

Achievable FSI Affects Value of the Property 

The market value of properties of the same size, in the same locality with different abutting Road Width, and different shapes, will differ. Higher the Abutting Road Width, higher the rate the property will fetch. 

Also, properties with good width or frontage. This is so because higher FSI could be achieved in a property having a wider Abutting Road, Frontage, and proper shape. This means more income by way of increased Floor Area that can be constructed and sold. 

For example, consider a plot of 2400 sq.ft on a narrow road of say, 15′ width. Further the property has got a small frontage. In this case full FSI 2 may not be possible.

This is because of the need to provide Set Back Spaces. Since the total constructible area may low, the profitability from the construction venture will also below. So, the price the Land will fetch also will below. 

What Are the Benefits of Increased FSI? 

Apart from allowing new constructions to build more floor area, as a result of this higher FSI, (earlier the FSI was 1.5 only), redevelopment activities are on the increase.

Buildings/apartments constructed years ago, with old FSI norms are being redeveloped now. This is a win situation both for the occupants/owners as well as for the promoters. 

How Constructable Area Is Calculated? 

FSI allowed is 2. This means, the total plinth area one can construct is twice the area of the plot. For example, if the plot area is 2400 sq.ft, the total plinth area of all floors that can be constructed in that plot can be up to 4800 sq.ft.

There are exemptions for some constructions while computing the Floor Area. Later in this Article we give the list of exemptions. 

The calculation of FSI is not that simple. The road width, plot width and height of the buildings also decide the constructable area. This is so because of the need to provide Set Back Spaces around the building. 

As a result, achieving the allowed FSI may not be possible many times. 

What is Setback Spaces? 

Set Back Spaces for Building Plan Approval mean the open space around the building. It’s the Space across front or sides or rear of a plot between the building and street alignment or boundary. The height of a proposed building, width of the plot, and abutting road width govern the Set Back Spaces. 

Why Setback Spaces? 

Set Back Spaces are essential for Building Plan Approval for a healthy and organized community living. It will provide light, ventilation, and privacy to the proposed building under consideration.

Neighbours also will continue to enjoy light, ventilation and privacy. Set Back Spaces will provide space for parking of vehicles. In times of emergency, the open space around the building will help movement of fire tenders.

Also, Set BackSpace may prevent the fire from spreading to neighboring buildings. 

Most importantly, Step Back Spaces have a bearing on the floor area that can be constructed. 
Because, though Floor Space Index (FSI) of 2 is allowed for Non-Residential Buildings, it (FSI) can be achieved only after providing for Set Back Spaces. 

Norms for Set Back Spaces 

The Tamilnadu Combined Development and Building Rules 2019, has put in place new guidelines on Set Back Spaces for Approval of Building Plans. The norms are different for Non-High-Rise Buildings and High-Rise Buildings.  The Non-High-Rise Buildings have two sets of guidelines. 

• For Buildings up to 16 dwelling units or 300 square meters of commercial buildings.  
• For Buildings exceeding 16 dwelling units or 300 sq meters of commercial buildings. Given below are the details. 

Set Back Spaces for Non-High-Rise buildings up to 16 dwellings or up to 300 square meters of commercial building:   

Front Set Back Space 

Abutting Road Width	Front Set Back
Up to 9 Meters	1.5 Meters
More than 9.0 Meters up to 18 Meters	3.0 Meters
More than 18 Meters up to 30.5 Meters	4.5 Meters
More than 30.5 Meters	6 Meters

Side Set Back Space 

Height of the Building	Plot Width	Side Set Back
Up to 7 Meters	Up to 9 Meters	1 Meter on one side
	Above 9 Meters	1 Meter on Either Side
More than 7 Meters Up to 12 Meters	Up to 6 Meters	1 Meter on One side
	Above 6 Meters Up to 9 Meters	1.5 Meters on One Side
	Above 9 Meters	1.5 Meters on Either Side

Rear Set Back Space 

Height of the Building	Rear Set Back
Up to 7 Meters	Nil
More than 7 Meters Up to 12 Meters	1.5 Meters

Set Back Spaces for Non-High-Rise buildings up to 18.30 Meters in height exceeding 16 dwelling units and exceeding 300 square meters of commercial building: 

Front Set Back Space 

Abutting Road Width	Front Set Back
From 9 Meters Up to 18 Meters	3 Meters
More than 18 Meters Up to 30.5 Meters	4.5 Meters
More than 30.5 Meters	6 Meters

Side Set Back Space/Rear Set Back Space 

Height of the Building	Side Set Back/Rear Set Back
Up to 7 Meters	1 Meter
More than 7 Meters Up to 12 Meters	1.5 Meter
More than 12 Meters Up to 16 Meters	2.5 Meter
More than 16 Meters Up to 18.30 Meters	3 Meter

Structures that are allowed in the Set Back Spaces in the case of Non-High-Rise Buildings 

1. Sun-shades not exceeding 0,6m. 

2. Motor room of area not exceeding 2 sq.m. each and height not exceeding 1.8m, without affecting parking and driveway requirements. 

3. In case of Non-High-Rise Buildings with height up to 9.0m, open single flight or spiral staircase or open double flight staircase so long as such structure do not fall within 0.50 m from the side boundary or 1m. from the rear or front boundary of the site or street alignment. 

4. A compound wall of height not exceeding 2.0m 

5. Watchman booth not exceeding 2.5m.x 2.5m. in size at each gate and height not exceeding 3m. 

6. Gate pillars without or with arches with a min. headroom clearance of 5.50m available at least to a width of 3.5m. 

7. Meter Rooms for meter boxes or electrical panels along the boundary wall or external walls of the building with the projections not exceeding 0.60 meters from the abutting walls and the open Transformer without affecting parking and driveway, subject to the safety measures stipulated by Tamil Nadu Electricity Board 

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