The area inside a house that can be ‘covered with a carpet’ is the net usable area. This is the space within the interior walls of an apartment and does not include the common areas, balconies, terrace, or shafts. It includes bedrooms, washrooms, living area and kitchen, and is usually about 70% of the built-up area (explained later).
As per the Real Estate (Regulatory and Development) Act, 2016, carpet area is defined as the net usable area in a property, excluding the external walls, exclusive balcony, verandah and terrace, wherein the word ‘exclusive’ refers to the exclusive use by the owner.
The only difference between carpet area and RERA carpet area is that the latter includes the thickness of the interior walls, whereas the former doesn’t.
Built-up area
This refers to the total area of a flat, including the carpet area, both internal and external walls, as well as balcony, verandah and terrace. Hence, the built-up area is bigger than the carpet area. This is the reason most builders and brokers use this area to market their properties.
This includes the built-up area and a proportionate share of the common areas in the building, such as the lift lobby and shaft, corridors, stairs, etc. Some developers also include the common facility areas, such as the swimming pool, parks, clubhouse, parking space, etc.

