Since there are not much changes in the rules, there is hardly any scope to raise the building height, says Suresh Kuppuswamy 

     Is the skyline of Chennai all set to change? Are we to soon have a Shanghai or a Manhattan make over for the city? If one has to go by the various reports published following the notification of the new Master Plan, then the answer is yes. What gives rise to this anticipation if not myth is the new rule that the permissible height of buildings can now exceed 60 meter. However, the rules as detailed in the master plan and the fine print point otherwise. Chennai’s skyl ine may not drastically change.

     A multi-storeyed building is defined as a building exceeding four floors or 15.25M height. The old rules allowed Multi-Storied Buildings only within Chennai city on plots having an area of 1500 m.sq. and abutting roads with a minimum width of 18 M. However, multi-stored buildings constructed as IT offices are permissible anywhere within Chennai Metropolitan Area (CMA). The maximum permissible height in the case of non-IT buildings within Chennai city was 60M or 1.5 times the width of the abutting road, whichever is higher. For IT buildings, it was 60M or twice the width of the road, whichever is higher.

     None of this has changed in the new Master Plan. Height restrictions for both the types of multi-storeyed buildings have been retained. Exceptions have been made only in the case of plots abutting 30.5 M wide roads where they can exceed 60 M.

     Even when the height restriction of 60M existed not many buildings in Chennai were built to reach this height. A 60M building could have at least 16 floors with an average floor height of 3.6M. There are not many buildings that are 16 floors and above in Chennai. Why did not the developers and individual property owners capitalise the existing provision of 60M height?

Inversely proportional

     One reason is that the height of the building does not automatically grant more buildability. The maximum buildability, which is Floor Space Index- FSI, is inversely proportional to the plot coverage factor. In other words, lesser the plot coverage more is the FSI . Plot coverage is the extent to which the building occupies the site on the ground floor, in short its foot print.

     To achieve the maximum FSI of 2.5, the building has to occupy only one third of the plot. When the ground coverage is 30 per cent, then it is possible to achieve permissible FSI of 2.5 with just 9 floors. Hence most of the MSBs in Chennai are in the range 9 to 11 floors or 40M in height. If one has to go further tall then the plot coverage or the foot print of the building has to reduce further which will result in lesser floor plate area in typical floors. This may not be preferred by all end users. Barring an increase in the open-to-sky area around multi-storeyed building there is no direct benefit to the owner or developer for increasing the height of buildings.

Setback requirement

     In addition, as the building becomes taller, the setbacks required all around also increases considerably. The setback requirement for Multi-storeyed building has been retained as 7M all around for buildings with 30M height and for every additional 6M in height, 1M extra needs to be added to the setback. Therefore for a 60M tall building, the setback requirements would be 12M. This means only plots with large area and wide frontage can reach the sky. Such plots are a rarity within city limits. In other words, smaller properties will not go for the height and will try to achieve the FSI within the heights available.

     Another possible reason for the relative lack of tall MSBs in Chennai is that they are also costlier comparatively. As the building becomes taller, they have to adhere to stricter structural safety and fire safety standards. Also the construction cost increases on account of higher lifting charges of building materials and labour. The owners of tall buildings have to pay more maintenance cost as well.

     The plot extent, plot frontage and the desired floor plate area are greater determinants of the skyline when the permissible FSI is limited. It is a myth that by simply removing the height restrictions beyond 60M on 30.5M wide road would automatically change Chennai’s skyline. As such there is no special incentive for taller buildings beyond 60M. The only beneficiaries of the new rule would be owners of large plots or projects where image-making by means of the greater height is important.

     However, the newly introduced concept of premium FSI of 1.0 for Multi-storeyed buildings would increase the height of MSBs by at least 3 floors. Normally the builders try to maximise the ground coverage or foot print for many reasons. Another factor that may have moderate effect is that the Multi-storey buildings would be henceforth allowed on roads of 12 M and 15M. However, the FSI for such buildings have been restricted to 1.5 and 1.75 respectively.

     One of the important factors that will deter any change in skyline is the available width of roads. There are hardly many roads within Chennai city limit that has more than 30M width. Hence the anticipated skyline change to fit an imagined international image is only wishful thinking. However, it is likely that the skyline in the outskirts of Chennai city and within CMA limits would change. MSBs are now permitted in any place within CMA. Given the fact that many layouts and access roads to the plots are narrow it is also not likely to happen.

The author is Professor and Head of the Department of Architecture, Anna University, Chennai.