Plot Coverage and Set Back Rules

The normal permissible FSI (Floor Space Index) for a special buildings, whether it is intended for residential or commercial use, is 1.5 which means that the maximum extent of construction in any plot cannot exceed one and half times the area of the plot. The factors that are related to achieving the prescribed FSI are governed normally by the extent of Plot Coverage and Set Back Rules.

Plot coverage is the extent of plot covered by the building(s) or structure and this is expressed in terms of percentage. It is actually a ratio of the built-up area over plot area. As per the rules of CMDA (Chennai Metro), for special buildings, the normal permissible Plot Coverage is 65 percent. It means that the plinth area of the construction proposed should not exceed 65 percent of the plot area. By this, it is implied that at least 35 percent of the plot area is to be left open to the sky permanently. The concept behind imposing a ceiling on the footprint of the proposed construction is to ensure that every plot gets sufficient sunlight, air, privacy and rainwater. Rain water harvesting will facilitate recharge of aquifer and help in promoting greenery around. The plot coverage is computed by taking into account all the projections at upper levels. Broadly speaking, it is the area of the shadow of the proposed building at noon, which is expressed in percentage of the plot area. It is to be noted that the plot coverage restriction has no bearing on the profile of a building.

For a special building, there are mandatory regulations in terms of the spaces to be left between the proposed construction and the boundary of the plot. They are known as Set Back Rules. The setback spaces ensure sufficient light, air and privacy not only for the occupants of the proposed building but also to the immediate neighbours. They also facilitate movement of vehicles around the building including fire tenders in case of an emergency. Besides, they provide spaces for parking vehicles. In some cases, they promote landscaping around the building. In addition, sewer lines with necessary inspection chambers are normally laid out in the open spaces around the building.

As per Development Control rules of CMDA the set backs are classified as Front Set Backs, Rear Set Backs and Side Set Backs. 

Side Set Backs are spaces to be left at the sides of a building and are governed by the height of a building proposed. The rules stipulate that they shall be a minimum of one-third the height of the building subject to a minimum of 3.5m. The Side Set Back need not be necessarily the same on both sides. CMDA permits a minimum of 3.5m on any one side provided the remainder of the total two-third of the building is left on the other side. 

Ex: For a building of 15m height, the side Set Back can be 3.5m on one side and 6.5m on the other side. By this option, a developer would be able to accommodate vehicles parking on the side having more width.

Set Back space is computed by taking into account the space left between the outer surface of the building proposed and the edge of the plot boundary. However, unsupported sunshades and wardrobes up to 0.6m and non-continuous balconies up to 1.0m projection are permitted in the Set Backs.

Structures in set backspaces

Unless or otherwise specifically provided for elsewhere in these regulations, no structure shall be constructed within the minimum prescribed set back spaces except the following:

In cases of non-multistoreyed buildings (including ordinary buildings) -

A.Unsupported sunshade, wardrobes, balconies, and other projections from the main walls, stated below so long as such structures do not fall within minimum prescribed set-back spaces more than what is prescribed below -

• Sun-shades 0.60m
• Non continuous wardrobes or built- in cub boards above ground floor 0.60m
• Open non-continuous balconies (above ground floor) 1.20m
• Open service verandah to kitchen (above ground floor) 1.20m
• Architectural projections above ground floor 1.00m
• Staircase open landing projections (not affecting driveway) 1.00m
• Cantilevered portico so long as it does not fall within 1.5m from the street alignment or boundary of the site whichever is closer.

The points 3-5 above shall be permitted in the setback spaces provided a minimum clearance of 0.5m for an ordinary building and 1.50m for a special building / group development and for any other non-MSB from the property boundary or street alignment whichever closer is made available.

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

C.In case of ordinary buildings, 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 1 m from the rear or front boundary of the site or street alignment. In case of residential buildings, structures like toilet, change room, garbage etc. not intended for human habitation and servant quarters are permissible provided it doesn't occupy more than one third of the plot width, 6m from rear boundary and 4 metres in height from ground level.

D.A compound wall of height not exceeding 2.0m.

E.Watchman booth not exceeding 2.5m. x2.5m. in size at each gate and height not exceeding 3 m.

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

G.Meter rooms for meter boxes / electrical panels along the boundary wall or external walls of the building with the projections not exceeding 0.60m from the abutting walls and the open Transformer without affecting parking and driveway, subject to the safety measures stipulated by TNEB.

The concept of premium FSI was introduced in the second master plan by CMDA, and is meant only for specific areas. The master plan permits a premium FSI of 0.5 over and above the normally permitted FSI would be given to special buildings (ground-plus-three floors or stilt-plus-four floors). For multi-storeyed buildings, the premium FSI was fixed at 1.

As per CMDA norms, the builders will have to pay guideline value of the virtual land to enjoy premium FSI. In simpler terms, if a builder gets normal FSI of 1.5 on a 100 sqft piece of land and if he wants to enjoy premium FSI of 0.5, he will have to pay the guideline value (fixed by the registration department) of 33.33 sqft of virtual land to construct the additional built-up area of 50 sqft.