The Carpet Area Confusion in Redevelopment Projects That Nobody Explains Clearly

You have lived in your flat for twenty years. The building is old, the structure is tired, and the society finally agrees to go in for redevelopment. The developer presents a proposal, and then comes a number that puzzles you. The carpet area being offered in the new building looks smaller than what you have now. You feel shortchanged. You start objecting.

But here is the thing. In most cases, the actual space you will live in has not shrunk at all. What has changed is how that space is measured. This is the carpet area confusion that derails more redevelopment negotiations in Maharashtra than almost any other issue.

Before you can understand the redevelopment problem, you need to get comfortable with three terms that the real estate world uses interchangeably but should not.

Carpet area is what it sounds like. The area within your flat where you could theoretically lay a carpet. It does not count the walls, the shaft spaces, or the open terrace. This is the number that matters for your daily life.

Built-up area adds a percentage on top of carpet area to account for wall thickness and certain common portions. In Maharashtra, municipal corporations generally add up to 20 percent over the carpet area to arrive at the built-up area for FSI calculation purposes.

Super built-up area goes further, sometimes adding 40 to 60 percent over the actual carpet area. This was the number developers loved during the pre-RERA era. It made pricing look lower than it actually was, because you were getting less usable space per rupee than the headline rate suggested.

Most older Mumbai housing societies were built and sold under MOFA, the Maharashtra Ownership Flats Act. Under that law, carpet area had a relatively loose definition. Balconies and internal partition walls were typically included in the carpet area figure. Terraces sometimes were too.

The result was that the carpet area stated in your old agreement was probably a little inflated compared to the actual space where you live and breathe. That balcony and those partition walls were quietly adding numbers to a figure that should have reflected only usable internal space.

When the Real Estate Regulation and Development Act came into force in 2016, it introduced a precise, statutory definition of carpet area under Section 2(k). Under RERA, carpet area is only the net usable floor area inside the apartment. It excludes external walls, service shaft areas, balconies, verandahs, and open terraces entirely. Internal partition walls are included, but nothing outside the apartment envelope counts.

Developers selling RERA-registered projects are legally required to advertise, price, and execute agreements based strictly on this carpet area figure. The old practice of quoting built-up or super built-up area is no longer permitted for registered projects.

Here is where the two legal regimes collide. Your old flat was sold under MOFA, with a carpet area figure that included balconies and internal walls calculated in a particular way. The new flat will be delivered under RERA norms, where those balconies are measured separately and not included in the stated carpet area.

Even if your new flat has the same or greater actual living space, the RERA-defined carpet area number on paper will almost certainly be lower than the MOFA-defined carpet area number from your original agreement. Studies have found a difference of roughly 5 to 8 percent between these two figures for typical residential buildings in Maharashtra, depending on structural complexity and internal wall configurations.

So when a society member looks at the Permanent Alternate Accommodation Agreement and sees a smaller carpet area number, they are not necessarily getting less space. They are seeing the same space measured by a stricter, more accurate ruler.

Knowing this is only half the battle. The other half is making sure your society negotiates effectively before signing anything with the developer.

The practical approach is to focus on usable carpet area rather than either MOFA or RERA definitions in isolation. A Project Management Consultant should measure the existing flats on usable terms before the feasibility study is prepared. The redeveloped flat must offer more functional living space than the existing one, regardless of what legal framework is being used to count it.

Societies that enter negotiations without this clarity end up comparing MOFA numbers with RERA numbers and concluding something went wrong when nothing did. That confusion benefits nobody except the developer who can avoid giving a genuine increase in living space.

The carpet area dilemma in redevelopment projects is fundamentally a measurement transition problem. Old buildings sold under MOFA used a broader, less precise definition that included balconies and certain wall areas. New buildings delivered after RERA use a tighter, legally mandated definition that excludes those components. The resulting 5 to 8 percent numerical gap does not mean residents are getting less space. It means the space is finally being measured honestly. Housing societies must understand this distinction before entering any redevelopment negotiation and must insist on higher usable carpet area as their non-negotiable ask.