Yingzao Fashi
The walls were built inclined toward the center, such that the natural force of gravity pushes the wall together. This inward inclination method was also used in the construction of Pagoda of Fogong Temple. The thickness of the tulou wall decreases with height as specified in Yingzao Fashi. The bottom two stories of tulou are solid with no window nor gun hole, windows are open only from the third to fifth stories, because rooms at the bottom story served as family storage rooms and the upper stories were living quarters.