The basement is where a project's FSI arithmetic is most often decided, because the same slab can be free space or charged space depending entirely on what goes on it.
Key takeaways
- Regulation 9.11.1 sets out two lists: uses permissible free of FSI, and uses permissible and counted in FSI.
- Free: parking, air conditioning and service plant, DG set and meter rooms, electric substations, effluent treatment plants, suction tanks and pump rooms, plus storage where the building is a data centre.
- Counted: household and goods storage, strong rooms and bank lockers, hospital rooms such as mortuary and cold storage, commercial use in a shopping centre's first basement, and anything strictly ancillary to the principal use.
- A basement flushing to average surrounding ground level may extend into side and rear margins up to 1.5 m from the plot boundary.
- Multilevel basements are permitted where the basement is used for parking.
- Every basement must be at least 2.4 m from floor to soffit, with ventilation of at least 2.5 percent of its area.
Two lists, one slab
Chapter 9, Regulation 9.11, UDCPR as updated 30 January 2025 begins by placing the basement: it shall generally be constructed within the prescribed setbacks and margins, with one or more levels. Then it divides what may go in it.
| Free of FSI | Permissible, and counted in FSI |
|---|---|
| Air conditioning equipment and other machines used for the services and utilities of the building | Storage of household or other goods, or ordinarily non-combustible material, incidental to the principal use |
| Parking spaces | Strong rooms, bank lockers, safe deposit vaults, laundry rooms |
| DG set room, meter room and electric substation conforming to required safety requirements | Radio or laser therapy rooms, post mortem room, mortuary, medical shop and cold storage for a hospital building |
| Effluent treatment plant, suction tank and pump room | Commercial use in the first basement, in the case of a shopping centre or shopping mall |
| Storage, only where the use is a data centre | Uses strictly ancillary to the principal use, and nursing quarters ancillary to a hospital in the first basement where it is 0.9 m to 1.2 m above ground level with proper ventilation |
The organising idea is easy to state once the two columns sit side by side. What serves the building is free. What serves the occupier is counted.
Air conditioning plant, pumps, substations and the cars themselves keep the building running, and the code does not charge development potential for them. Storage, lockers, a mall's retail floor and hospital support rooms are things people use, and they are charged like any other floor. The data centre exception proves the rule: for that occupancy, storage is plant.
Two provisos that change a layout
A flush basement may reach into the margins. Where the basement is proposed flushing to the average surrounding ground level, it may be extended in the side and rear margins up to 1.5 m from the plot boundary. That is a meaningful gain on a tight plot, and it is conditional on the basement not projecting above ground.
Multilevel basements are permitted if used for parking. The regulation says so directly, which is what makes deep parking stacks possible where the margins above ground are already committed.
Getting cars into it is handled elsewhere. Regulation 6.7(g) permits a ramp for the basement within the side and rear marginal distances, subject to Chapter 9, Regulation 9.12, Ramp*, and Regulation 8.1.1(viii)(e) requires basement parking to have at least two separate ramps of adequate width and slope for entry and exit, preferably at opposite ends.
The physical minimums
Chapter 9, Regulation 9.11.2 sets two figures that decide whether a basement is usable at all.
- Height: every basement shall be, in every part, at least 2.4 m from the floor to the soffit of the beam.
- Ventilation: a ventilation area of not less than 2.5 percent of the area of the basement, with any deficiency met by adequate mechanical ventilation through blowers, exhaust fans or air conditioning systems.
The 2.4 m figure is the same clear height Regulation 9.16 sets for a stilt and Regulation 9.13 for a podium, so the three parking levels a building might use share one dimension.
The word that ties it to Chapter 6
Read this regulation alongside Regulation 6.8(ii), because the two are drafted to work together and neither is complete alone.
6.8(ii) excludes a stilt, podium or basement from the FSI calculation where it is used exclusively for parking, including passages, and the staircase, lift duct and lobby within it. It then separately excludes basements used for the purposes in Regulation 9.11.1(i) to (iii), which is the free list above.
And Regulation 6.6 supplies the converse: if part of the basement is proposed for habitation, or for construction counted in FSI, that part is measured in the P-line of the respective floor.
So a basement is not exempt as a place. It is exempt use by use, continuously, and a change of use later changes the FSI position of the space it happens in.
What to check
- List what the basement is sanctioned for, and sort it against the two columns above.
- Confirm the height is 2.4 m in every part, not on average.
- Check the ventilation area against 2.5 percent of the basement's area, and what mechanical provision makes up any shortfall.
- Check whether the basement flushes to ground level if the design relies on extending into the margins to 1.5 m.
- Count the ramps on any basement parking, since two are required, preferably at opposite ends.
Where the filings come in
The register records where parking sits only in the loosest terms: about 88 percent of projects file an open space row and a closed or covered row, and only 2.1 percent name a basement at all, as the parking data article sets out. So the filing will rarely tell you whether a project's covered parking is in a basement, a stilt or a podium, which is exactly the distinction the FSI exemption turns on.
What the register does hold, free, is the filed land area, the buildings and their floors, the promoter's extension history with the stated reasons, the certifying professionals, and any complaints or litigation with case numbers, all at reragenie.com.
ReraGenie's project analysis, Rs 2,999 for one project, reads the full filing and the documents behind it, and the area consolidated report covers a whole micro-market at Rs 2,999 for the first project and Rs 1,999 per additional one.
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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