How feasibility software computes permitted buildable area in Tamil Nadu from FMB geometry, land-use zone and road width under TNCDBR 2019, and why it belongs in diligence.
Corporates buy land in acres but build in square metres of permitted floor area. The conversion runs through the Tamil Nadu Combined Development and Building Rules, 2019: the use zone fixes what activities are permitted, FSI caps the floor area against the plot, coverage and setbacks shape the footprint, and the width of the abutting road can cap height and FSI regardless of zone.
Two parcels of identical acreage and price can therefore differ by a large factor in what they can carry. Paying acreage prices without computing the envelope is how that difference becomes a write-off.
Four inputs decide most of the answer: the parcel's surveyed geometry from the FMB, including any splay or water-body margin; the land-use zone from the master plan, CMDA in the Chennai Metropolitan Area, DTCP elsewhere; the abutting road's status and width, measured rather than assumed; and any overlays, CRZ, aerodrome funnels, heritage or industrial buffers, that subtract from the envelope.
Each input is a record with a source: FMB from Survey, zone from the sanctioned land-use maps, road status from local body and highway records. Feasibility built on assumed inputs is a sketch; built on verified inputs, it is diligence.
With inputs verified, the rule engine applies TNCDBR: permissible FSI and coverage for the zone and use, setbacks by building height and plot depth, parking demand by use, height caps from road width and any overlay, and premium-FSI eligibility where applicable. The output is a quantified envelope, footprint, floors, gross floor area, and a list of the binding constraints, which is what design and pricing teams actually need.
Running this as software means every shortlisted parcel gets the same computation in minutes, so site selection compares true buildable capacity rather than brokered acreage.
We report buildable area alongside title: a parcel that is legally clean but carries 40% less envelope than the pro-forma assumed is a graded finding with a price consequence. Conversely, a verified envelope larger than assumed is negotiating room. Either way, the number reaches the deal team before terms close.
Build Scope, the feasibility tool inside LandLens, runs exactly this computation, geometry in, envelope out, with the binding rule cited for every constraint, so the answer is checkable rather than asserted.
Primarily the land-use zone and the proposed use under TNCDBR 2019, modulated by plot characteristics and abutting road width, with premium FSI available in defined cases. The binding number is parcel-specific, which is why it should be computed, not assumed.
Yes, when the inputs are verified records: FMB geometry, sanctioned zone, measured road width and applicable overlays. The rules are deterministic; the risk is bad inputs, which is why feasibility belongs inside diligence.
Yes. TNCDBR ties height and intensity to the abutting road's width and status. A parcel on a narrow or unrecognised road can lose a large share of its assumed envelope, regardless of zone.