RERA Carpet Area vs. Super Built-Up: How Navi Mumbai Builders Quietly Add 15% to Your Bill

Key takeaways:

• Under RERA, carpet area is the net usable floor area within your home's walls — balconies, terraces, and duct areas are not included. Brochures and builder agreements often quote "saleable" or "super built-up" area that can be 8–15% higher.
• A typical 2BHK in Kharghar Sector-20 that sports a 900 sq. ft. "super built-up" label may have a RERA-registered carpet area of only 630–670 sq. ft. — check the difference before you calculate price per square foot.
• Builders in Navi Mumbai commonly pad the carpet area by including balconies, air-conditioner niches, external ducts, and even the foyer outside your door in the "saleable" figure, even though they are not part of your carpet.
• Use the MahaRERA portal to download the approved floor plan and layout — the annotated carpet area on plans is legally binding for your agreement.
• A smaller carpet area than advertised reduces your resale value, increases your price per square foot, and triggers higher stamp duty and registration than necessary if the agreement hasn't been corrected.

---

Intro: The fine print in your brochure

When you walk into a sales office in Kharghar or Panvel, the glossy brochure proudly states "2 BHK, 900 sq ft carpet area." It feels like a good deal for ₹1.2 crore. But when you read the MahaRERA filings carefully, that "carpet area" might be 790 sq ft — and the difference is not just a calculator glitch. It is a pricing game that affects your loan eligibility, stamp duty, registration, and even the flooring you'll need to buy.

Most home buyers in Navi Mumbai don't realize the discrepancy until they sign the purchase deed — by then, it's too late. Let's dissect the legal wording.

The legal definition: What exactly is "carpet area" under RERA?

Under the Real Estate (Regulation and Development) Act, 2016, "carpet area" is defined as the net usable floor area of an apartment, excluding the area covered by the external walls, areas under services (chimneys, ventilators, air ducts), and exclusive balconies or verandahs. In plain English: the area you can walk on inside the finished flat, from inner wall to inner wall.

This is different from "super built-up area" (BSP) which adds a percentage for common areas like lifts, lobbies, and staircases. It is also different from "saleable area" which is what cohesanies use in brochures — often used loosely.

Most critical: RERA obligates the builder to specify the carpet area in the agri—and it's that figure—not the super area—that gets registered with MahaRERA under the project details. If a builder says "size of flat: 1000 sq ft," but the RERA carpet area is 900 sq ft, the difference is 10% of the deal’s size.

A real scenario from a Kharghar Sector-20 high-rise

Let's take a hypothetical (but realistic) 2BHK in one of the new towers in Kharghar's Sector 20 — an area known for its central park views and proximity to CIDCO exhibition centre.

• Brochure says: 2 BHK, Saleable Area: 850 sq ft, BSP ₹9,000/sq ft.
• RERA filing (check the project on mahaonline.gov.in): Carpet Area: 790 sq ft.
• Your math: 850 – 790 = 60 sq ft missing. Multiplying ₹9,000 × 60 = ₹5.4 lakh, which you're paying for not actual internal space. That's almost 6% of your home price.

And that's before you extract the area of the balcony. Under the law, the balcony is not part of your carpet. If the balcony is 25 sq ft, then your true walkable area is 765 sq ft. Compare that with what you thought you were buying — a difference of ~10.5%.

In older, pre-RERA buildings, builders often factored in thicker walls, vents, and duct lines. Now, a notoriously common trick is to include the air-conditioner niches (the little step outside your window) as part of the "carpet" — despite being an open-air, non-usable extension. Some projects go so far as to list spaces for façade stringcourses and geometric patterns that aren’t spatial at all.

Where Navi Mumbai builders quietly pad the numbers

• Balconies: a 4x8 ft balcony adds 32 sq ft, which builders may label as "carpet".
• Air conditioner platforms: plastic or aluminium niches about 2x2 ft each, sometimes added in columns for several air conditioners.
• Duct areas: shafts for pipes and air ventilation systems (often in the bathroom or kitchen) count as "non-usable" in RERA, but some builders add their footprint to the carpet.
• Walls: internal walls between bathrooms, bedrooms, and lobbies are often not excluded properly in filings.
• The "drive" / common corridor in front of the flat — for the whole floor and the entry lobby — sometimes gets factored into the super built-up but not carpet; ensure you're not paying for this.

A buyer's best trick is to measure the carpet at site using a measuring wheel or digital laser. Compare these numbers with the registered plan.

How to cross‑check with the MahaRERA portal

1. Visit maharera.maharashtra.gov.in.
2. Click on "Projects" on the top menu.
3. Enter the builder's name (exactly as registered) or the project's name, and the district (Raigad for Kharghar–Panvel side, or Thane for certain parts like parts of Vashi, though most are Raigad).
4. Look for “Approved Plans & Layout” under the project details. The PDF will show the purge lines and the carpet area as per the registering authority.
5. Open the floor plan and find the flat number. The area in write (usually in sq ft) is the carpet area. Any difference from the brochure or agreement's share certificate is a red flag.

Impact on registration, stamp duty, and future resale

Here's why the carpet area matters beyond square feet:

• Stamp duty and registration — In Maharashtra, stamp duty is calculated on the higher of the sale price or the ready-rekoni value — and often that ready-rekoner is prepared per super-built area. If you arepaying ₹1 on a carpet area of 800 sq ft, while the actual carpet is 700, your registration cost is unfairly high. Getting it corrected can sometimes give you a refund application, but that’s time-consuming.

• Brokerage — Brokerages frequently charge on the saleable area (the larger figure). Always clarify if it's on carpet or SSP. If you are told