Is the south or north roof triangular or flat?

In the north (north of Huaihe River in Qinling Mountains), there is less rain and more drought, and the roofs are mostly flat, so the anti-leakage measures are simple; The rainy season stretches in the south, and heavy rains often strike. The concept of dredging is adopted in the rain protection of residential buildings, mostly sloping roofs and triangular roof trusses. The slope of the splayed beam is 1:2, and the double slope is commonly known as' Four Waters', with an inclination angle of 26 34'.