Yes, the rule is real. Under an August 2022 amendment to the Tamil Nadu Combined Development and Building Rules, properties within 500 metres of a Metro Rail corridor, existing, under construction or sanctioned, pay premium FSI charges at 50% of the normal rate. It lowers a developer's cost of building more floor area; it does not automatically lower flat prices.

Updated 10 October 2026. We read the government gazette notifications directly. Where a figure comes from the 2019 rules and may since have been amended, we say so.

What exactly does the rule say?

  • G.O. Ms. No. 152, Housing and Urban Development Department, 18 August 2022, published in the Tamil Nadu Government Gazette on 24 August 2022, substituted rule 30(5)(ii) of the TNCDBR 2019.
  • The text: for Metro Rail corridors, existing, under execution and proposed with administrative sanction, properties within 500 metres measured from the centre line of the corridor pay premium FSI at 50% of the applicable premium FSI charges.
  • G.O. Ms. No. 15 of 14 January 2024 added the same concession for the MRTS (Chennai Beach–Velachery, with the St. Thomas Mount extension) and three suburban rail corridors, listed as Transit Oriented Development corridors.
  • Because the 2022 rule covers lines under execution, the Phase 2 corridors, including the Poonamallee–Porur–Vadapalani stretch, fall within it.

What are FSI, premium FSI and the 2.0 and 3.25 figures?

FSI (floor space index) is the total built floor area allowed, divided by the plot area. An FSI of 2.0 on a 10,000 sq ft plot allows 20,000 sq ft of floors. Premium FSI is extra floor area above that, which a developer buys from the planning authority.

  • Non-high-rise buildings (up to 18.3 m): maximum FSI 2.0 under the TNCDBR 2019 tables.
  • High-rise buildings: maximum FSI 2.0 on a 12 m road, 2.5 on a 15 m road and 3.25 on an 18 m road or wider.
  • Premium FSI on top of that, as a share of the normally allowable FSI: up to 50% on roads of 18 m and above, 40% on 12–18 m roads and 30% on 9–12 m roads (rule 49).
  • The charge, in the 2019 rules: 50% of the guideline value for the extra area in non-high-rise buildings, and 40% in high-rise buildings. Within 500 m of a metro corridor, half of that.
  • So the reported '3.25 versus 2.0' is broadly right as a description of high-rise versus standard limits, but it is a function of road width and building type, not a special metro FSI.

What does the concession save, in rupees?

An illustration with an assumed guideline value of ₹8,000 per sq ft, chosen only to make the arithmetic clear. Check the actual value for any address: Chennai stamp duty calculator

  • High-rise, outside the corridor: premium FSI costs 40% of ₹8,000, about ₹3,200 per sq ft of extra floor area.
  • Within 500 m of a metro corridor: about ₹1,600 per sq ft.
  • On 1,200 sq ft of extra floor area, roughly one flat's worth, that is about ₹38.4 lakh against ₹19.2 lakh, a saving of about ₹19.2 lakh to the developer.

Will it make flats near the metro cheaper?

Not directly. The saving is to the developer, and only on the premium FSI portion of a project. Flat prices near a working metro are set mainly by demand, which tends to rise with better transit. What the rule mainly does is make it more viable to build taller and denser near stations, which over time can mean more homes, and more choice, close to the line.

For a buyer the useful questions are practical: is the project actually within 500 m of the corridor's centre line, did it use premium FSI, and does the approved plan match what is being built? In July 2026, Credai Chennai asked CMDA to clarify whether a site qualifies if only part of it falls within the 500 m zone, after authorities applied the rule differently, as reported by Construction/Facilitator. That is a developer-side issue, but it shows why you should ask for the approved plan.

Phase 2 and the Poonamallee–Porur belt

The first Phase 2 stretch, Poonamallee Bypass to Vadapalani via Porur, was reported to be opening on 11 October 2026; see Chennai Metro Poonamallee–Vadapalani Line Is Open: Timings, 11 Stations, Fares & Property Impact (2026) for stations and fares, and Homes Near Chennai Metro's Poonamallee–Porur Stations: 22 Projects by Station Area and Budget (2026) for homes near each station.

Projects in our listings along this belt include, as indicative ranges from developer information, October 2026, subject to the developer's price sheet: Casagrand Zenith, Manapakkam, ₹0.85–1.50 crore (Casagrand Zenith); Prestige Bella Vista, Iyyappanthangal, ready to move, ₹0.70–2.50 crore (Prestige Bella Vista Iyyappanthangal); DAC Balmandaisa, Mount–Poonamallee Road, Porur, ₹1.19–2.72 crore (Dac Balmandaisa Porur Mount Poonamallee Road); and Casagrand Ventra, Kattupakkam, ₹1.01–3.37 crore (Casagrand Ventra Kattupakkam Poonamallee High Road). We have not checked whether any of these used the premium FSI concession, and their distance from the corridor varies.

A buyer's checklist near a metro line

  • Measure the walking distance to the nearest station, not the straight-line distance to the corridor.
  • Ask for the CMDA planning permission and check the approved FSI and number of floors against the brochure.
  • Check the TNRERA registration on rera.tn.gov.in and the latest quarterly progress.
  • Think about noise and construction near the viaduct and stations, especially on lower floors.
  • Compare price per sq ft with similar projects 1–2 km away; the premium for proximity should be reasonable.