The interior wall of the staircase is the public area, and the public area of the house is the abbreviation of the shared public building area. The sum of it and the building area of the suite constitutes the building area of a commercial house. At present, there are no clear laws and regulations on the treatment of shared area in China. Because of the uncertainty of shared area, it has become the focus of controversy in the process of real estate transactions.
Public area refers to the total area of public corridors, staircases, floor lobbies, water tanks, elevators, etc. set up in residential buildings to facilitate users' access, normal communication, and ensure life. When buyers purchase commercial houses, the real estate association will apportion the public area to users and include it in the user's building area. The shared common area includes the indoor and outdoor stairs (internal walls) outside the set (unit) doors, internal and external corridors, public vestibules, passageways, elevators, power distribution rooms, equipment floors, equipment rooms, structure transfer floors, technical floors, air conditioning machine rooms, fire control rooms, guard rooms on duty serving the whole floor, garbage rooms in buildings, and stairwells with enclosure structures vacated from the roof Elevator machine room, water tank room, etc.