The sunken ceiling in ancient buildings

This is a way to deal with the suspended ceiling in traditional buildings in China, because the large roofs of traditional buildings in China are basically supported by the lifting beam system. There will be a large part of roof space indoors. At first, it was to prevent dust from falling, and later it was feudal hierarchy, so the roof was treated in various ways.

Generally, there are three kinds: smallpox, algae well and rolled shed. The general Fang Gezi is "smallpox", and the common "corridor" or "single cylindrical arch" of pavilions and pavilions in the south is the shutter door. In some advanced buildings, the concave dome used in the center of the hall is called "algae well". This structure of the Forbidden City is the "algae well".

Caisson in Ming Dynasty is different from caisson in Qing Dynasty. In the Ming dynasty, mirrors were painted on the ceiling, with lotus petals around them or Yunlong painted on the ceiling. In the Qing Dynasty, the dragon was simply carved, and the Zhu Xuan in the mouth looked like a chandelier from below, but it also had the function of a mirror, also called "Longjing".

As for classification, caisson is not a structural part, but it obviously belongs to "Joinery Work".