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Permitted Is Not Buildable: How FSI, Setbacks and Road-Width Rules Shape Housing Supply in Kerala, Tamil Nadu and Andhra Pradesh

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Permitted Is Not Buildable

Permitted Is Not Buildable: How FSI, Setbacks and Road-Width Rules Shape Housing Supply in Kerala, Tamil Nadu and Andhra Pradesh

Floor Space Index (FSI) is usually treated as the main lever for increasing urban housing supply, but this CPPR study shows that the floor area a plot can actually deliver depends on how FSI interacts with coverage limits, setbacks, road-width requirements and height thresholds. The study reviews the residential building rules of Kerala, Tamil Nadu and Andhra Pradesh provision by provision and applies a buildable-unit model to a common 2,500 sq m plot. The results show that stated FSI is a poor guide to how many homes can be built. Although stated FSIs range from 2.0 to 5.0, the number of buildable EWS units on the same plot ranges only from 153 to 263. Kerala and Tamil Nadu can build all the floor area their FSI allows, but Andhra Pradesh, with the highest FSI of 5.0 in Amaravati’s S3 zone, loses 31 per cent of it to height-graded setbacks and open-space rules and ends up only 14 per cent ahead of Kerala. Each state is constrained by a different rule: Kerala by a uniform FSI that is used up at five floors and offers no reward for building taller, Tamil Nadu by a higher FSI that is unlocked only above 18.30 m on wide roads, and Andhra Pradesh by setbacks that shrink the footprint as height increases.

The study also finds that smaller plots, where much affordable housing is built, lose the most, because fixed-width setbacks take up a far larger share of their area. On a 500 sq m plot, Andhra Pradesh can build only a third of its permitted FSI. Drawing on Indian and international evidence from cities such as Singapore, Tokyo, Copenhagen, São Paulo and Houston, the report argues that reform must look beyond the FSI figure itself. It recommends that states:

  • publish effective development capacity alongside nominal FSI,
  • remove step changes at height thresholds,
  • scale setbacks to plot size,
  • make density charges cost-based and transparent, and
  • move towards performance-based standards for daylight, ventilation and fire access.

For Kerala, it specifically proposes raising the high-rise threshold with fire-safety safeguards, extending the fee-free FSI of 5.0 to private affordable housing, and resolving the conflict between recreational-space and setback rules. Together, these measures would help the three states convert more of the development rights they already grant into homes without compromising safety or liveability.

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