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UFS vs UFA

Updated: Jul 17, 2023

What is the difference between UFS and UFA?


Usable Floor Space (UFS)

(實用樓面空間) means any floor space other than staircases, staircase halls, lift landings, the space used in providing water-closet fitments, urinals and lavatory basins and the space occupied by machinery for any lift, air-conditioning system or similar service.


Use:

  • To calculate the area required for refuse storage and material recovery chambers in residential developments


Usable Floor Area (UFA)

means the aggregate of the areas of the floor or floors in a storey or a

building excluding, unless otherwise specified, any staircase, public circulation space, lift

landings, lavatories, water-closets, kitchens in flats, and any space occupied by machinery

for any lift, air-conditioning system or similar service provided for the building.


Use:

  • To calculate the assumed number of occupant (using occupancy factor) that will use the exit routes. This is the Discharge Value.

  • To calculate sanitary fitment in a development. UFA is used to calculate the the assumed number of occupant through a ratio. For example, the Building Ordinance assumes the rate of 1 person per 9m2 of UFA. The number of occupant is then used to deduce how many sanitary fitment is needed.

  • To calculate required lighting and ventilation. For example, to calculate whether the window areas of a room is at least 1/10 of UFA of the room and whether openable window areas of a room is at least 1/16 of UFA of the room.


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