Wooden Framing

 

 

The Chinese have developed a distinctive wooden framing system to support the roof.  Tile roofs are very heavy. Rather than bringing all the weight down onto the walls, which is how the triangular truss common in Western construction works, the system developed in China distributes gravitational forces downward and then out through the wooden frame.   The weight-bearing frame provides flexibility for the placement of walls, windows, and doors. Non-load-bearing walls can be made of many different materials, such as brick, earth, wood, bamboo, or even corn or cotton stalks.

Two main kinds of framing systems developed: pillars-and-beams (tailiang), and pillars-and-transverse-tie-beams (chuandou). Examples of these framing systems can be seen below. The tailiang framing system is on the left, and the chuandou system is on the right.

The main components are vertical pillars that begin at ground level, short vertical supports called purlins, and horizontal beams connecting the purlins.  

Can you identify these three basic components and determine their function in the diagrams below? 

Diagrams of framing systems from a Song dynasty building manual

SOURCE:  Li Jie, (1035-1110), Yingzao fashi zhushi. ed. Liang Sicheng (Beijing: Zhongguo jianzhu gongye chubanshe, 1983), p. .
Can you describe how either system might be adapted to support curved roofs? What would change to support roofs with pronounced curves?

How do you think these types of framing systems are better suited than the Western triangular truss to support a curved roof ?

HINT:  The distance between purlins can be altered according to specific ratios.

Can you see how the weight is distributed from this photograph of the inside of a roof?

Pillars-and-beams wooden roof support system, from a building in the 

Beijing area

SOURCE:  Photograph courtesy of Ronald G. Knapp, 1987, Lugouqiao area, Beijing

 

Whereas building rammed earth walls required little technical skill, carpenters often needed to be called in to construct the framing system. To the left, carpenters in the still relatively well-forested Sichuan province work on a beam for wood framing.

Carpenters at work preparing a beam

SOURCE:  Photograph courtesy of Ronald G. Knapp, 1981, Emeishan area, Sichuan province

A pillars-and-transverse-tie-beams system under construction in Sichuan province is shown to the right. This chuandou system is often used in the south where the houses are deeper.

Note the beam that extends past the frame.

Why might it be so long and wide?

ANSWER:  This beam will support the weight of extended eaves at the corner.
SOURCE:  Photograph courtesy of Ronald G. Knapp, 1981, Emeishan area, Sichuan province

 

Can you tell what is supporting this roof?

Brick house with timber structure exposed in Guangxi province

SOURCE:  Photograph courtesy of Ronald G. Knapp, 1985 Guilin, Guangxi province
In frames of buildings for wealthier families, or for use in palaces or temples, the function of the cantilevered beam shown two pictures above might be replaced by complex, or corbelled, brackets, shown below. They are the layered green pieces below the eaves.

What function do you think the corbelled bracket serves?

ANSWER:  The bracket braces the upward lift of the heavy eaves. In more expensive buildings, eaves are frequently extra heavy because they are tipped with decorated drip tiles to keep water away from the walls. Brackets also add ornamental accents to a building.

 

 

 

Corbelled brackets and drip tiles, 

Hall of Celestial Piety, Forbidden

City, Beijing

SOURCE:  Photography courtesy of Lenore Hietkamp, 1998. Hall of Celestial Piety, Forbidden City, Beijing.