What is the difference between gross floor area and net floor area in building measurement?

Explanation:

Gross Floor Area (GFA):

• The gross floor area includes all enclosed space within the building measured up to the outer face of the exterior walls.
• In other words, the gross floor area encompasses all the floor space within the outer boundary of the building, including the space occupied by walls and partitions but excluding porches, ducts, shafts with no openings, or interior courts.

Net Floor Area (NFA):

• Net floor area refers to the usable floor area and is also known as net-usable area or occupied area. 
• In other words, the net floor area represents the actual usable floor space within the building, and it excludes areas occupied by walls, columns, and other structural elements.

Additional information:

Plinth Area:

• Plinth area shall mean the built-up covered measured at the floor level of the basement or of any storey.

Carpet Area:

• Carpet area shall mean the floor area of the usable rooms at any floor level.

The gross floor area includes all enclosed space within the building, while the net floor area includes only usable space. Hence option (1) is correct.