FSI is a ratio. Almost every dispute about it is a dispute about the numerator, and UDCPR settles that in two regulations that are rarely read together.
Key takeaways
- Regulation 6.6 computes built-up area on the P-line: the outer periphery of the construction, floor by floor, including everything except ducts, voids and the items in Regulation 6.8.
- Open balconies, double height terraces and cupboards are expressly inside the P-line, irrespective of their use or function.
- Regulation 6.8 lists nine categories outside it, from parking stilts and podiums to atriums, service structures, terraces and telecom towers.
- The hinge is the word exclusively. A stilt or podium is excluded while used exclusively for parking; the moment part of it is habitable, 6.6 pulls that part back into the P-line.
- The register carries a filed land area on essentially every project and a permissible built-up area on 96.7 percent, but the two cannot be divided into a reliable FSI: 7.3 percent produce a ratio above 5.0.
One line around the building
Chapter 6, Regulation 6.6, UDCPR as updated 30 January 2025 is four sentences and it does the whole job.
Built-up area for the purposes of FSI is the outer periphery of the construction, floor wise, known as the P-line, including everything but excluding ducts, voids and the items in Chapter 6, Regulation 6.8, Exclusion of Structures / Projections for FSI Calculation*.
Then the sentence that most often surprises a buyer reading their own agreement:
The open balcony, double height terraces and cupboard shall also be included in P-line of respective floor, irrespective of its use / function.
An open balcony is open, and it is still built-up area. So is a double height terrace, and so is a cupboard recessed into a wall. The regulation forecloses the argument in advance with "irrespective of its use or function", which is drafting aimed at exactly the reading it denies.
The P-line is not confined to this chapter, which is worth knowing because it turns up where you would not expect it. UDCPR uses it for area statements, requiring each floor's area to be calculated to the periphery line of construction excluding ducts and voids. And Ulhasnagar's regularisation entry uses the same line to measure the consumed FSI of an existing unauthorised structure, which is one half of its protected FSI calculation.
One measurement convention, doing very different work in three places.
The nine exclusions
Chapter 6, Regulation 6.8* lists what sits outside the P-line. Read as a set, the logic is consistent: things that serve the building rather than occupy it, and things open to the sky.
| Category | What is excluded |
|---|---|
| Projections | Structures, projections, features and ornamental projections of glass facade permitted in marginal open spaces under Regulation 6.7(a), (c), (d), (e), (f)(iii), (g), (j) and (k) |
| Parking | Stilt, multi-storeyed floors, podium or basement if used exclusively for parking including passages, and the staircase, lift duct and lobby within it; and basements used for the purposes in Regulation 9.11.1(i) to (iii) |
| Building services and covers | Porches, canopies, lofts, ledge or tand, shelves, air conditioning plant rooms, lift well, lift machine room, and service floor not exceeding 1.8 m in height below the beam, for hospitals, shopping malls, plazas, three star and above hotels and like buildings, and other buildings above 15.0 m |
| Utilities | Structures for water, grey water, wet waste or effluent treatment plants, rainwater harvesting pump rooms, electric cabins of sub-stations or generator set area, electric meter rooms as required, and refuse or garbage chutes and shafts for wet and dry garbage separately with collection chambers |
| Open ground features | Rockery, well and well structures, plant nursery, water pool, platform around a tree, fountain, bench, chabutara with open top and unenclosed sides, ramps, compound wall, gate, slide or swing, steps outside the buildings, domestic working place open to sky, overhead water tank on top of the building, and refuge area for high rise buildings |
| Telecom | Telecommunication tower, antenna and allied activities |
| Atrium | An atrium in any type of building, which may be enclosed on top by a transparent or opaque sheet |
| Open to sky | Open to sky terraces, top of podium, and an open to sky swimming pool on the top terrace or top of podium with its plant room |
| Recreational open space | Structures permissible in recreational open space under Regulation 3.4.7 |
Two of those rows carry a condition inside them that does the real work.
The service floor exclusion is not general. It is available for hospitals, shopping malls, plazas, three star and above hotels and like buildings, and other buildings above 15.0 m in height, and only up to 1.8 m below the beam. A service floor in a low rise residential building is not on this list.
The refuge area exclusion is tied to high rise buildings and to the specification in Regulation 9.29.6, not to any floor a developer designates as refuge.
The word the whole thing turns on
Regulation 6.8(ii) excludes a stilt, multi-storeyed floor, podium or basement if used exclusively for parking. Regulation 6.6 supplies the other half: if part of the stilt, podium or basement is proposed for habitation purpose, or for construction which is counted in FSI, then such construction shall also be measured in the P-line of that respective floor.
Read together, the exclusion is conditional and continuing, not a status the structure acquires once. A podium with a gym on part of it is a podium with FSI on part of it. The two regulations are drafted to make that automatic rather than to require an assessment.
For a buyer this is the clause behind a familiar situation: amenity space carved out of a parking level after sanction is not a free upgrade, it is consumed FSI, and where it was not sanctioned that way it is unauthorised construction.
The 2 December 2021 corrigendum sharpened exactly this point. It inserted "exclusively" and "including passages" into 6.8(ii), and deleted a maximum 10 sq m limit elsewhere in the sub-regulation. Before that amendment the parking exclusion read more loosely than it does now.
What the register can and cannot tell you here
This is a rare case where the filings carry the raw material and still cannot answer the question, and saying so is more useful than a chart that pretends otherwise.
Every published project files a land area: 46,636 of 46,654 outside Mumbai, essentially complete. And 96.7 percent also carry a permissible built-up area figure. Dividing the second by the first should give the FSI the project was permitted.
It does not.
Source: ReraGenie analysis of the MahaRERA project registry, 41,833 of 45,125 published projects outside Mumbai carrying both figures, excluding 3,292 whose ratio exceeds 5.0, captured 11 August 2026
The excluded 3,292 are the finding, not a nuisance. That is 7.3 percent of projects producing an implied FSI above 5.0, and the 99th percentile of the untrimmed set is above 20. No provision in Chapter 6 permits anything close to that, so those numbers are not FSI; the two fields are simply not always measured over the same ground.
The obvious explanation is phase registration, where a project registers one phase of a larger sanctioned layout, so the built-up figure and the land figure describe different extents. This analysis could not confirm that from the filings, because the phase block is populated on every project in the corpus and so does not separate the two groups.
Either way the conclusion holds and it is worth stating plainly: you cannot audit a project's FSI from its MahaRERA filing. The register records what was declared, not how the P-line was drawn, and the figures in it are not a substitute for the sanctioned plans. Even the trimmed distribution above is offered as a shape, not as a measurement, and 19.3 percent of it sitting between 3.0 and 5.0 should be read with the same caution.
What to check
- Ask what is inside the P-line before comparing two schemes, because balconies, double height terraces and cupboards are in it and buyers routinely assume otherwise.
- Check what the stilt, podium and basement are sanctioned for, since Chapter 6, Regulation 6.8* excludes them only while they are exclusively parking.
- Confirm a service floor exclusion is actually available for that building type and height before relying on it.
- Treat the ancillary area FSI layer separately, as it is computed on the proposed FSI excluding 6.8 items, per the note to Table 6-A in the congested area rules.
- Read the sanctioned plans for the numerator, not the register, then the UDCPR FSI rulebook for the denominator side.
Where the filings come in
The code says how built-up area is measured. The register says what the promoter declared, building by building, and whether it was delivered. Those are different questions and the honest answer to the first one is not in the register at all.
What the register does answer well: ReraGenie's project analysis, Rs 2,999 for one project, reads a project's full MahaRERA filing, including the filed land area, the promoter's extension history with their stated reasons, the slip between original and current completion dates against the median for the same pincode, construction progress against the eleven activity checklist building by building, and complaints and litigation with case numbers. The area consolidated report covers a whole micro-market at Rs 2,999 for the first project and Rs 1,999 per additional one.
Every project's filing is free to read at reragenie.com/projects. For the form side of the same question, see setbacks and marginal distances and the height rules, and the question that comes before all of it is which rulebook governs your plot.
Source: Unified Development Control and Promotion Regulations for Maharashtra, UDCPR as updated 30 January 2025. Sanctioned under the Maharashtra Regional and Town Planning Act, 1966.
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