可用GFA)，可出售，樓面面積的分別

1. Gross Floor Area ﹝建築面積﹞
The area contained within the external walls of the building measured at each level (including basement) excluding services rooms. Plot ratio = GFA/Site Area
[ref: Building (Planning) Regulation 23(3)]
This term measures how much had built over a site, direct relationship on price of land and bulk of building mass.

2. Usbale Floor Area ﹝實用樓面面積﹞
Means the aggregate of the area of the floors in a storey or a building excluding toilets, kitchen and services room.
[ref: Building (Planning) Regulation 2, Means of Escape Para. 4]
This affect the number and disposition of staircase, lift and exit of a building.

3. Salable Floor Area ﹝實用面積﹞
The exterior enclosing wall of a unit (e.g. a flat or a shop unit) including balconies & verandahs. Measure to the mid of a wall if the enclosure is a party wall between two units. Excluding common areas e.g. corridor, staircase, services room and lift area.
This would affect the efficiency of a unit ﹝實用率﹞.
[ref: LACO CM40A App. A]