INTRODUCTION

According to the Yingzao fashi, there are two kinds of carpentry: large and small. "Large," or structural, carpentry (da muzuo) concerns the design and construction of the structural wood frame and its components, including the characteristic bracket sets. "Small," or non-structural, carpentry (xiao muzuo) involves elements like window frames and ceilings.

The Yingzao fashi, or Building Method, is a Chinese government manual published in 1103. In thirty-four chapters, it discusses topics from site work and stonework to the estimation of materials and labor. It was edited by Li Jie (c. 1065-1110), the vice director (later the director) of construction in the court of the Huizong emperor (reigned 1101-1125) of the Song dynasty (960-1127).^Ref.1 As one of only two books on architecture surviving from the imperial era, it has been a critical document in the study of Chinese architecture. In fact, the "discovery" of the Yingzao fashi in 1919 and its subsequent reprintings led directly to the establishment of the field of architectural history in China, and it has remained an important object of research.

The two major studies of the Yingzao fashi both focus on structural carpentry. Liang's annotated and illustrated version is, to use his own metaphor, a translation into modern language and graphic conventions, a translation which allows us to read the previously unreadable.^Ref.2 Chen recognizes explicitly that structural carpentry is about rules, and works to make the rules clearer, more complete, and more consistent.

We are interested in the rules, too, not for their own sake, but for the larger system of structural carpentry which they define. This system, simply put, is a kit of parts. It consists of preformed components which are combined in various ways to produce many products. A well-known kit of parts is the construction toy, Lincoln Logs, which are assembled to form log cabins.

This article introduces this system of structural carpentry through examples of the two main types of rules defining the kit of parts: those specifying the parts, and those specifying the ways in which the parts are assembled.

COMPONENTS

If we are dealing with a kit of parts, then what are the parts? The Yingzao fashi discusses many components, from columns and beams to brackets and blocks. Here we examine just one, the smoke tree block (lu dou),Ref.3 the bottom-most component of the bracket set. (Figs. 1, 2, 3) It is defined like this:

Figure 1: Bracket sets: Three bracket sets at Xian dian, Jin ci, Taiyuan, Shanxi. The smoke tree block is the lowermost component in each set.

Place it on the top of the column. It is 32 fen square, but, if placed on a corner column, it is 36 fen square. It is 20 fen high: the upper 8 fen are the ears, the middle 4 fen are straight, and the lower 8 fen are sloped. Open mouths [i.e., cut slots] 10 fen wide and 8 fen deep. Take 4 fen off the lower-most four faces and flute 1 fen.

(10749 bytes) Figure 2: Smoke tree block: A typical prototypical component: the smoke tree block (lu dou). Its dimensions are given not in absolute units but in fen, a modular unit which has one of eight values from 19.2 to 9.6 mm, depending on the rank of the building. Thus its height, defined as 20 fen, can range from 384 to 192 mm. The smoke tree block is the bottom-most component in the bracket set. (From Liang, Yingzao fashi zhu shi, 242.)

Figure 3: Smoke tree block: VRML model of a smoke tree block.

There is, in addition, a rule applying to a larger set of blocks:

In four-eared blocks, separate the mouths with wrapping ears. The wrapping ears are located at the inner walls of that mouth which is parallel to the jump, and are 2 fen high and 1.5 fen thick. In a smoke tree block, double these dimensions.^Ref.4

These rules show certain important features. First, as a definition of physical form, they are - thanks to Liang's "translation" - unambiguous. The parts in the kit are precisely defined.

Second, the rules specify the way in which this component is combined with others: the smoke tree block is placed on the top of the column and not, for instance, on the ground. This simple example barely proves the point, but we will encounter more elaborate rules of this type when we discuss the roof section.

Finally, the fen, the unit of dimension, is modular: its absolute size varies. Thus the rules define prototypical, not actual, components; in virtual modeling terms, primitives, not instances. Because of this crucial distinction, we can use virtual models to illustrate the process of applying rules to generate products, which we discuss in a future article. Here, though, we continue with the fen and other modular units.