actual carpet area 1000sft and common area 30% it should be 1300 but builder sell it as 1430 sft saying 30% common area. where as they are adding 43% loading to your actual cost of apartment.
You are 100% correct, and you have caught onto one of the oldest mathematical tricks used by real estate builders to inflate super built-up area (SBUA).
Builders do not add 30% to your carpet area; instead, they ensure that the common area makes up 30% of the final total saleable area. This reverse calculation forces a 43% loading premium onto your actual usable space. [1, 2, 3]
## The Breakdown of the Math Trick
Here is exactly how the builder's math works out behind the scenes to arrive at 1,430 sq. ft.:
* Your Logic (Forward Loading): You took the $1,000\text{ sq. ft.}$ and added 30%.
$$\text{Carpet Area } (1000) \times 1.30 = 1,300\text{ sq. ft.}$$
(Actual loading = 30%)
* The Builder's Logic (Reverse Loading): The builder uses a division formula to ensure the common area represents exactly 30% of the total area sold to you.
$$\frac{\text{Carpet Area } (1000)}{1 - \text{Common Area \% } (0.30)} = \frac{1000}{0.70} = \mathbf{1,428.57\text{ sq. ft. (Rounded to 1,430)}}$$
(Actual loading on your carpet area = 43%) [4, 5, 6, 7, 8]
## Why Do They Do This?
1. Artificially Low Base Price: It allows the builder to market a lower "price per square foot" while collecting the exact same amount of money. [9]
2. Padding Common Areas: They shift the cost of grand entrance lobbies, wide corridors, and massive clubhouses directly onto your unit's invoice. [10, 11]
## What Does the Law Say?
Under the Real Estate Regulatory Authority (RERA) guidelines in Hyderabad, builders are legally mandated to disclose and sell properties based strictly on Carpet Area. [12, 13]
However, many private developers circumvent this by quoting a lower per-square-foot price on the Super Built-up Area rather than a higher per-square-foot price on the pure Carpet Area. If you look at your draft sale agreement, the exact carpet area must be written explicitly. [14, 15, 16]
