The carpet area of a flat or commercial property is the net usable area that will be available to the buyer within the physical confines of the property. This is calculated from the inner side of one wall to another. For example, if the length of the living room measured from the inner side of one wall to the inner side of the facing wall is, say, 15 feet and the breadth of living room is, say, 10 feet, the carpet area of the living room is 150 feet. Similarly, the carpet areas of the kitchen, bedroom(s), bathroom(s), toilet(s) and passage are calculated and added to arrive at the total carpet area of the flat.
The built-up area (BUA) consists of carpet area plus the area covered by the inner and outer walls of the property along with areas of flower beds, dry balcony, etc. BUA is basically the aggregate area covered by the property.
The super built-up area consists of BUA and the proportionate area of common spaces of a building such as lobby, passages, staircase(s) and elevator(s). The SBUA basically seeks to charge the buyer the proportionate cost of areas of common spaces.
It should be noted that BUA or SBUA have no legal sanction and, therefore, no developer mentions it in the agreement for sale of the property. Only the carpet area of the property has a legal sanction and, therefore, finds mention in the agreement for sale.
BUA and SBUA are just ploys of the developers designed to impress the buyer in three ways: first, the buyer gets the impression that he is buying a larger property for the same price; second, he may feel that the builder is selling a property of comparable size at a lower rate; and third, the developer charges more for a property by including areas of walls (in the case of BUA) and proportionate areas of common spaces (in the case of SBUA) in the saleable area of the property.
So, if you wish to compare the cost and the area of the flat or commercial property with another flat or commercial property, the comparison should be based on carpet area and not BUA or SBUA.