FSI and FAR in Tamil Nadu: Developer Guide to the TNCDBR 2019 Rules

This guide is for developers and acquisition teams checking how much they can build on a plot in Tamil Nadu under the Tamil Nadu Combined Development and Building Rules 2019 (TNCDBR 2019). It is not a substitute for the planning authority’s written decision on your parcel.

In short

• Non-high-rise buildings (up to 19.50 m) get a flat FSI of 2.0 under Section 35, whatever the road width. G.O.(Ms) No.194 (26.10.2026) raised the high-rise line from 18.30 m to 19.50 m.
• High-rise FSI depends on the abutting road: 12 m gives 2.0, 15 m gives 2.5, 18 m or wider gives 3.25. Below 12 m, a plot does not qualify for high-rise.
• Premium FSI adds 30%, 40% or 50% on top, by road width. The charge is 50% of guideline value on the extra area for non-high-rise and 40% for high-rise. Treat it as a scenario until the authority approves it.
• Open Space Reservation (OSR) is nil up to 3,000 sqm, 10% of area excluding roads above that, and mandatory land (no payment in lieu) above 10,000 sqm.
• A plot within 500 m of the centre line of a Metro Rail corridor pays 50% of the normal premium charge. Get written confirmation first.

FSI is built-up area divided by plot area

FSI (Floor Space Index) is total built-up area divided by plot area. An FSI of 2.0 on a 1,000 sqm plot permits 2,000 sqm of built-up area across all floors. FAR (Floor Area Ratio) means the same thing, but TNCDBR 2019 uses FSI throughout its operative sections.

Separate two numbers. Permissible FSI is the limit the rules set. Achievable FSI is lower once ground coverage, setbacks, minimum floor height, parking and, on larger layouts, OSR are applied. A team that benchmarks FSI without those limits overestimates saleable area and underestimates the capital needed to cover the gap.

• Ground coverage: the building footprint divided by plot area.
• Built-up area (BUA): the sum of floor areas including walls.
• Carpet area: usable interior area. Its ratio to BUA depends on the design, so it is a project assumption, not a rule.
• Premium FSI: extra ratio you can buy from the planning authority.

One rulebook covers all of Tamil Nadu

TNCDBR 2019 replaced the earlier separate CMDA and DTCP building rules with one framework. It applies in every planning authority area: the Chennai Metropolitan Area (CMDA), municipal corporations, municipalities, town panchayats and village panchayats governed by DTCP.

Two sections set FSI for most developments:

1. Section 35 covers non-high-rise buildings (height up to 19.50 m) and sets a flat FSI regardless of road width.
2. Section 39 covers high-rise buildings (height above 19.50 m) and sets FSI by the width of the primary abutting road.

The 19.50 m line also drives setbacks and minimum road-width requirements. G.O.(Ms) No.194 (Housing and Urban Development, 26.10.2026) raised it from 18.30 m. Many teams still use the older 15-metre or 7-storey rule of thumb, or the 18.30 m line from the 2019 text. 19.50 m is the operative standard now.

Non-high-rise: FSI is 2.0 on any road

For buildings within 19.50 m, Section 35 sets a flat FSI of 2.0. It applies across the CBA (Central Business Area), EWS (Economically Weaker Section) and Other Area designations. Road width does not change it. Road width only affects the premium FSI percentage you can buy on top.

Example: a 2,400 sqft plot (about 223 sqm) permits 4,800 sqft of FSI area. If a feasibility model assumes 78% efficiency, that implies about 3,744 sqft of carpet area. The real ratio must come from the proposed design and the applicable area definitions.

Non-high-rise is simpler to model but tighter on setbacks and ground coverage. On a narrow residential plot, a 4-floor design usually hits the setback limit on per-floor footprint well before FSI becomes the binding constraint.

High-rise: the abutting road sets the FSI

For buildings above 19.50 m, Section 39 sets FSI by abutting road width. A road below 12 m rules the plot out of high-rise entirely. The standard rules have no variance for this.

Abutting road width	Permissible FSI (high-rise)	Max BUA on a 10,000 sqft plot	Difference vs 18 m+ tier
Below 12 m	Not permissible	—	—
12 m – below 15 m	2.0	20,000 sqft	−12,500 sqft
15 m – below 18 m	2.5	25,000 sqft	−7,500 sqft
18 m or wider	3.25	32,500 sqft	—

The road creates a steep value gradient: on a 10,000 sqft plot, FSI 2.5 versus 3.25 is 7,500 sqft of FSI area. A site measurement alone does not settle the qualifying road width. Check the road-space definition and Rule 39’s prescribed road-length conditions with the competent authority before you commit to a high-rise scheme. Rule 39 also provides for a road-width certificate where a qualifying-road subdivision is absent from the FMB sketch.

Premium FSI: extra area, with approval

Tamil Nadu lets developers buy additional built-up area from the planning authority. The extra percentage depends on road width and applies whether the building is high-rise or non-high-rise.

Abutting road width	Additional FSI purchasable
9 m – below 12 m	30% of permissible FSI
12 m – below 18 m	40% of permissible FSI
18 m or wider	50% of permissible FSI

On a 15 m road with a non-high-rise building (FSI 2.0), the 40% allowance adds 0.80 FSI and takes total built-up area to 2.80 times the plot. On a high-rise plot on an 18 m road (FSI 3.25), the 50% allowance adds 1.625 FSI, for a theoretical maximum of 4.875.

G.O.(Ms) No.194 rewrites the Rule 39 high-rise table (FSI 2.0, 2.5 and 3.25 on 12, 15 and 18 m roads) and removes the 50% coverage row. Rule 49 is unchanged, but confirm with CMDA or DTCP before counting on premium FSI for a high-rise. Premium FSI still needs planning approval, so treat it as a scenario in feasibility until the authority confirms that the parcel and design qualify.

Premium FSI cost depends on building type, not road width

The charge is calculated on the additional built-up area (not the total BUA), using the plot’s guideline value and a factor set by building type. People often mislabel this as a road-width factor.

• Non-high-rise (up to 19.50 m): 50% of guideline value (₹/sqft) × additional BUA (sqft).
• High-rise (above 19.50 m): 40% of guideline value (₹/sqft) × additional BUA (sqft).

Example, non-high-rise on a 15 m road: a 10,000 sqft plot at FSI 2.0 gets an additional 0.80 FSI (40% of 2.0), which is 8,000 sqft. At a guideline value of ₹3,500/sqft and a 50% factor, the premium charge is 8,000 × ₹3,500 × 0.50 = ₹1.40 crore.

Use the TNREGINET-published value for the specific street and village. The Tamil Nadu Guideline Value Lookup lists the TNREGINET benchmark per street and village. Confirm it against TNREGINET before you price this line. Guideline values are revised periodically, and a stale figure can materially mis-estimate this line.

Ground coverage decides how many floors you need

Ground coverage is the second limit on using your FSI. Once you know the permissible and premium FSI, it sets how many floors you need to fit that area.

Building type	Maximum ground coverage	Basis
Non-high-rise	No fixed cap	Governed by setback requirements; the rules give no percentage
High-rise	~50% planning estimate	Setbacks rise with height (7m up to 30m, 16m above 87m); G.O.(Ms) No.194 removed the 50% row

Example, high-rise on a 10,000 sqft plot: the footprint at the 50% estimate is 5,000 sqft. With FSI 3.25, total BUA is 32,500 sqft. Minimum floors: 32,500 ÷ 5,000 = at least 7 floors.

This bites on mid-size plots of 5,000–15,000 sqft, where the developer may want fewer floors but FSI forces more to fit the permissible BUA inside the footprint. The FSI / FAR Calculator derives minimum floor count from your plot area, road width and building height. Setbacks also remove part of the plot from the footprint. On a narrow plot, cumulative setbacks can push effective ground coverage below the 50% estimate and cut the per-floor footprint well below what FSI headroom suggests.

Frontage is a design check, not a number

A plot can qualify for high FSI on paper and still fail the frontage test for the intended building type. The rules do not give a universal 6-metre or 12-metre frontage minimum for these two categories.

• Non-high-rise: test the design against the applicable setbacks and access rules. Minimum abutting road width under Rule 35 varies by building size and use.
• High-rise: test the design against setbacks on all sides and the access rules. The minimum abutting road is 12 metres for the lowest high-rise FSI tier.

Frontage does not replace the rule’s road-width, access and setback requirements.

OSR takes land off the top

Open Space Reservation (OSR) is land reserved for community recreation under TNCDBR 2019. Rule 41 covers specified building developments and Rule 47 covers layouts and subdivisions. OSR affects the physical building envelope, but Rule 39 expressly permits FSI benefit for OSR land in the stated high-rise circumstances. Do not automatically subtract OSR land from the FSI calculation.

For a simplified middle-tier estimate with no internal-road deduction:

• Payment in lieu: 10% × (site area − 3,000 sqm). Convert that area to the unit of the official guideline value, then multiply by that value.
• Land: 10% of the site area excluding roads.

The competent authority must confirm the applicable area and valuation. Confirm the applicable Rule 41 or 47 route with the authority for plots in the middle tier.

Example, a 1-acre layout (about 4,047 sqm) at a guideline value of ₹3,500/sqft:

Metric	Value
OSR tier	3,001–10,000 sqm (land or fee)
Area used for fee calculation	4,047 − 3,000 = 1,047 sqm
Land option (10%, assuming no roads)	404.7 sqm (~4,356 sqft)
Equivalent land for fee option (10%)	104.7 sqm (~1,127 sqft)
Indicative payment in lieu	~₹39.44 lakh (1,126.9 sqft × ₹3,500; use current GV)
Area remaining outside OSR	~3,642 sqm if land is reserved; 4,047 sqm if payment in lieu is accepted

For layouts, Rule 47 requires the reserved land and public roads to be transferred to the local body by registered gift deed before layout sanction. Budget the conveyance and approval steps into the schedule, calculate both land and fee scenarios from the current rule text, and get the authority’s parcel-specific determination. OSR can also apply to building developments under Rule 41, so do not assume an undivided, single-building site is exempt.

Metro corridor plots pay half the premium charge

Rule 30(5)(ii) charges properties within 500 metres of the centre line of an existing or proposed Metro Rail corridor 50% of the normal premium FSI rate. It does not state the same concession for every MRTS or suburban rail corridor. It changes the charge, not the permissible FSI percentage.

Scenario	Premium FSI charge	After Metro discount
10,000 sqft, non-high-rise, 15m road, GV ₹3,500/sqft	₹1.40 crore	₹70 lakh
20,000 sqft, high-rise, 18m+ road, GV ₹4,000/sqft	₹5.20 crore	₹2.60 crore

Get written confirmation of corridor status before you put the discount in a feasibility model. The 500 m is measured from the corridor centre line, not from the nearest station. The FSI / FAR Calculator has a Metro corridor toggle. Use it only after the eligibility check.

For Chennai acquisitions in corridors served by the existing and Phase 2 Metro network, the discount is a material feasibility lever, especially on larger high-rise plots where premium charges run to several crores. See our Chennai land acquisition guide for corridor-specific context.

CMDA and DTCP start from the same rules

Both CMDA and DTCP areas use TNCDBR 2019 as the starting point for FSI review. The competent authority, the applicable master plan and any special-area restrictions must still be checked for the parcel.

Dimension	CMDA (Chennai Metropolitan Area)	DTCP (outside CMDA)
Governing rules	TNCDBR 2019	TNCDBR 2019
Section 35 FSI (non-HR)	2.0	2.0
Section 39 FSI (high-rise)	Road-width tiers (same)	Road-width tiers (same)
OSR determination	Rule 41 or 47 and site history	Rule 41 or 47 and site history
Building-plan approval authority	Confirm with CMDA / local body	Confirm with DTCP / local body
Premium FSI decision	Confirm with competent authority	Confirm with competent authority
Official portal	cmdachennai.gov.in	DTCP

Historical subdivision and master-plan records can affect a parcel’s OSR treatment. Get the registered subdivision instruments and prior approvals before assuming a historical exemption applies. For agricultural land converted to non-agricultural use and then subdivided, assess OSR at layout sanction as well as the separate land-use permission. See our guide to agricultural land conversion in Tamil Nadu for the approval sequence.

Verify FSI before the letter of intent

Complete FSI verification before the letter of intent. Once you have committed to a price based on a development scheme, finding the FSI assumption wrong means repricing the deal or absorbing a loss.

Check	What to verify	Source
Official road width	Confirm road space and qualifying length under Rule 39	Local planning office / CMDA
Building height intent	Confirm high-rise vs non-high-rise basis; check 19.50m threshold	Design brief
Metro corridor status	Written confirmation of 500m corridor proximity	CMDA / DTCP
Frontage measurement	Verify street-facing edge against FMB and survey	FMB/TSLR tool
OSR applicability	Check plot size and layout vs single-building determination	TNCDBR 2019 Rule 41/47
Guideline value	Pull current ₹/sqft from TNREGINET for premium FSI cost modelling	Guideline Value Lookup
Land use classification	Confirm residential, commercial, or mixed-use designation	Applicable master plan / planning authority
Conversion status	Confirm required land-use conversion for agricultural-origin land	Land conversion records
Encumbrance	Check for mortgages, attachments, or pending litigation	EC verification
Planning approval status	Check if plot is in approved layout or unapproved	Local authority records

Most of these are document checks, not site inspections, and you can run them in parallel once you have the survey number and patta details. Road width carries the highest risk. A 1-metre error in road classification can move the permissible high-rise FSI from 3.25 to 2.5, cutting maximum BUA by about 23% on the same plot (7,500 sqft less on a 10,000 sqft plot, from 32,500 to 25,000 sqft).

Premium FSI on a 15 m high-rise plot costs about ₹2,050 per extra carpet sqft

This example shows how the rules interact. The regulatory assumptions come from Rules 39 and 49. The carpet-area estimate is a separate, illustrative design assumption.

Inputs: plot 10,000 sqft (929 sqm); abutting road 15 m; building height 20 m (high-rise); guideline value ₹4,000/sqft; no Metro corridor.

Output	Value	Basis
Classification	High-rise (>19.50 m)	Section 39
Permissible FSI	2.5	Section 39: 15m road
Max BUA (permissible)	25,000 sqft	10,000 × 2.5
Ground coverage (estimate)	50% (5,000 sqft footprint)	Planning estimate; setbacks set the limit
Min floors required	5 floors	25,000 ÷ 5,000
Additional premium FSI	40% of 2.5 = 1.0	12–18m road tier
Max BUA with premium	35,000 sqft	25,000 + 10,000
Additional BUA (premium)	10,000 sqft
Premium charge factor	40% (high-rise)
Premium FSI charge	₹1.60 crore	10,000 × ₹4,000 × 0.40
Illustrative carpet area (permissible FSI area × 78%)	19,500 sqft	Design assumption, not a statutory ratio

At permissible FSI alone, the plot yields about 19,500 sqft of carpet area across 5+ floors. Premium FSI adds another 7,800 sqft of carpet area (10,000 × 0.78) for ₹1.60 crore, roughly ₹2,050/sqft of additional carpet area before construction costs. Whether that is worth paying depends on the achievable sale price per sqft in the location. Use the FSI / FAR Calculator to run this with your own plot area, road width, guideline value and Metro corridor status.

What this means for you

A developer’s land team: model high-rise FSI from the confirmed qualifying road width, not the road you measured, because a 1-metre road misclassification that moves high-rise FSI from 3.25 to 2.5 cuts maximum BUA by about 23%. Run ground coverage and OSR before you quote saleable area, and treat premium FSI and the Metro discount as scenarios until the authority confirms them in writing.

A single-plot buyer building non-high-rise: your baseline is 2.0 on any road, so setbacks and ground coverage will usually limit the design before FSI does. Road width matters here only for how much premium FSI you could buy, and that still needs approval.

A land owner or seller: a plot’s worth to a developer moves with its abutting road width, its OSR position and any Metro corridor eligibility. Have the road certificate, subdivision records and prior approvals ready, because the buyer’s FSI assumption will rest on them.

---

Sources: the Tamil Nadu Combined Development and Building Rules 2019, especially Rules 30, 35, 39, 41, 47 and 49; TNREGINET for parcel-specific guideline values. Check subsequent amendments and obtain parcel-specific confirmation from the planning authority before finalising a development plan.