Total Built Up Area: The construction cost calculations for your plot will depend on the Covered Area, Half Covered Area, Basement and Open Area. The summation of these areas form the total built up area.
Covered Area: It includes rooms, lift lobby, toilet, guard room,staircase, toilets, underground water tank, rain water harvesting pit, etc.
Half Covered Area: It includes balcony area, sunken courtyard, area with slab but not enclosed by wall like car parking area, etc.
Basement: It Includes retaining wall and staircase, lift shaft, lift lobby.
Open Area: It includes area of shaft/courtyard on each floor, area which is open to sky including the terrace, non-load bearing chajja area on each floor, etc.
All these areas further depend on the FAR Consumption. Some families consume the full FAR of the plot and build the maximum number of floors on their plot, others might just want to build the number of floors in which their family can live comfortably in.