The future of Mumbai’s skyline may resemble that of Manhattan’s today. In a decision that could have far-reaching implications for the city, the state government is taking a relook at the present restrictions on the vertical limit for buildings in Mumbai.

The Mumbai Transformation Support Unit (MTSU), state government advisory body, has undertaken a World Bank-funded study that would ultimately lead to a Floor Space Index (FSI) mapping for the city.

Explaining the concept, MTSU project director UPS Madan said, “Unlike Mumbai, most developed cities of the world do not have the concept of uniform FSI. An exercise in FSI mapping would be a more rational approach wherein different areas will be granted varying FSI. It would depend on factors such as whether the area is residential or commercial, its proximity to business districts, public transport corridors or green areas.”

The report, which is being prepared by a team of planners and economists led by World Bank appointed urban planner Alain Bertaud, will be ready in another couple of months. According to Madan, the World Bank team will submit the basic formula for area specific FSI and mapping while local planners with knowledge of the situation on field will carry out the detailing.

The Floor Space Index (FSI) — the permissible built up area on a plot — is 1.33 for most of Mumbai. Over and above this, constructions in suburbs can load transfer of development rights and can consume a maximum FSI of 2. The concept of additional FSI in Mumbai at present is scheme-specific rather than area-specific. For instance, projects under the Slum Rehabilitation scheme, Urban Renewal scheme, the proposed cluster redevelopment scheme, townships, MHADA colonies and redevelopment of old buildings under Development Control Regulation 33/7 enjoy higher FSI than other areas.

“Depending on how the study reviews FSI use in the city, we will make necessary amendments to the Development Control Rules,” said TC Benjamin, principal secretary for the state Urban Development department.

Madan added that the study will take a look at FSI usage in cities such as Singapore, New York and Seoul. “The norm for residential FSI across most cities if 0.5 to 4 depending on factors such as size of apartments. In case of bigger apartments, more FSI is granted considering low density in the area. For commercial districts the FSI is as high as 10 to 25,” said Madan.

Developers in Mumbai have for long being demanding higher FSI in order to correct the demand-supply mismatch.

“Where even cities like Chennai and Hyderabad have a high FSI of 2.5, Mumbai was too conservative in its FSI policy. A differential FSI hand in hand with infrastructure development is a good idea. However with most projects in Mumbai being redevelopment projects, there won’t be an immediate decrease in prices unless there is government intervention on resettling existing tenants or clear land titles as in the case of Dharavi,” said developer Mayur Shah from the Marathon group.

Urban planners have welcomed the move albeit with some reservations. “Cities should be planned with varying FSI, like high FSI for low density higher income group colonies or low FSI to protect historic areas like Khotachiwadi. But any such study on FSI should also address the issue of affordable housing and infrastructure development through some regulatory mechanism,” said Anirudh Paul, director, Kamala Raheja Vidyanidhi Institute of Architecture.