1. Introduction
The early 20th century of Korea, during its Japanese Colonization period, marks a tumultuous period of political and social change, thereby showing the inevitable juxtaposition of exchanges with Western countries, the impact of colonial rule, and modernization. As for architecture, new materials and construction techniques were introduced, and therefore, buildings that were completely different from the previous form—so-called pre-modern—of architecture began to appear [
1,
2]. During this time, interesting building types could be found: a single building showing various construction methods and heterogeneous exterior forms intertwined with many styles of multiple cultures. This raises the following questions: Is there a close relationship between the construction method (structure and material) and the exterior (mass and form) of a building? Does architecture function as an image representing a specific country or culture?
The National Archives of Korea has released approximately 26,000 architectural drawings generated by the Japanese Government-General of Korea during the Japanese Colonization period [
3]. These drawings are well preserved, so it is possible to check the detailed appearance of the buildings as they were first planned, despite all of them having been demolished. According to these drawings, most cases had a Western truss structure for their roofs, a condition that confirms the inflow of Western architectural building techniques, including truss-building techniques, through the Japanese Government-General of Korea [
4]. When a truss is used inside, its triangular shape is also reflected on its exterior, and it is common that the proportion or shape of the roof is significantly different from that of the roof of ‘traditional Korean’ architecture. However, while scrutinizing this archive, the authors found very unusual and interesting cases in which trusses were used inside whereas the exterior had the appearance of traditional Korean wooden architecture. An exemplary case is shown in
Figure 1, which is an architectural drawing of the building used as the Korea Pavilion (Korean Pavilion) for the 1914 Tokyo Taisho Expo. Although the use of the truss is clearly confirmed in the section drawing, its roof looks like that of the traditional Korean architecture from the outside, as shown in the elevation drawings of
Figure 2. In other words, this building deviated from the convention that ‘a roof made of truss structures usually has a flat slope on its exterior’, forming the ‘exterior’ of traditional Korean architecture with a curved slope and protruding eaves.
Figure 3 is an analytic diagram showing the interior and exterior structure of a typical traditional Korean architecture in the upper part and the Korea Pavilion at the Tokyo Taisho Expo in the lower part to depict the uniqueness of this building, making it easier to see the difference. In traditional Korean timber architecture, roof tiles are placed above the layer of soil (in light yellow), which is placed on the wooden plates over the timber frame (in yellow) composed of columns and beams. The exterior of the roof is formed of a smoothly curved surface with repeating layers of roof tiles, and it is common to construct an ‘eaves space’ under the roof by extruding building components called
seokkarae (rafters, shown in blue) as cantilevered. In the Korea Pavilion at the Tokyo Taisho Expo, the truss (in dark yellow) and various building components (in blue and brown) were integrated to embody the ‘appearance’ of traditional Korean timber architecture.
If so, did precedent studies deal with buildings like the above Korea Pavilion at the Tokyo Taisho Expo? Kim Tae-young, who summarized the introduction process of the truss in Korea and its types, categorized the truss types of the period into three main categories [
7,
8,
9]. The first type is where the structure and exterior of a truss roof of the West are applied as they are, and the second type is where a truss is applied to a Japanese-style roof structure. Both of these types are different from the Korea Pavilion at the Tokyo Taisho Expo in that they have the ‘flat-sloped roof’, which is distinct from the exterior roof form of traditional Korean architecture.
Figure 4 shows a section drawing and photograph of Jeonggwanheon Hall in Deoksugung Palace [
10], classified as the first type in the study of Kim Tae-young.
The third type suggested by Kim Tae-young is where the truss system is partially applied to the traditional Korean timber architecture. Although the truss itself is not used, some diagonal building components are added to the existing Korean or Japanese-style column-beam roof structure to apply the truss system. The extent of the change is not significant, and there are only a few cases of this type. Kim Tae-young mentions Iksan Nabawi Church as a representative example of this third type [
11]. Although its exterior looks like a traditional Korean roof, composed of Korean roof tiles, a roof curve, and eaves, the internal structure is composed of a Japanese timber structure strengthened with the principles of truss structure by adding
bitdaegong, diagonal building components (
Figure 5). In other words, the exterior appearance resembles that of a traditional Korean roof, but the Japanese roof structure and truss structure coexist inside.
This third type looks similar to the Korea Pavilion at the Tokyo Taisho Expo in that this structure has a style—partially applying the building principles of the truss by adding diagonal building components—that was not commonly found in the quintessential Korean-style roofs. However, there is a big difference between these two cases as the main structural frame was not thoroughly replaced with the Western truss in the Nabawi Church, and therefore, the Korea Pavilion of the Tokyo Taisho Expo should not be included in the three types categorized by Kim Tae-young. To sum up, the Korea Pavilion at the Tokyo Taisho Expo can be considered as a very peculiar case because it has a Korean-style roof form, uses a Western truss inside, and was designed by the Japanese, thus exhibiting multiple layers of hybridity and being marginalized from the scope of each country’s architectural history study. Although this pavilion was built in 1919, its architectural drawings were released in 2008 [
12], which is later than Kim Tae-young’s study. This might be the reason why this pavilion was not considered in Kim’s study. Other than his study, it is difficult to find relevant studies. The lack of precedent studies on this transposition might have stemmed from the fact that these architectural drawings were produced by the Japanese rulers, or it may be due to the tendency that these buildings’ visage was regarded as mere mimicry of Korean-style buildings. These aspects could have contributed to the difficulty of these cases finding their position within the study of architectural history in Korea or Japan.
In the National Archives of Korea [
13], the authors found a total of 11 drawings of buildings with structures and exteriors similar to those of the Korea Pavilion at the Tokyo Taisho Expo. Nine of them are the drawings of the Korea Pavilions at the expositions hosted by Japan in 1914, 1921, 1929, 1930, and 1932, and one each for the museum and the science hall. In addition, four cases were found among the architectural drawings of the buildings that were newly constructed in the Changdeokgung Palace between 1908 and 1910. These drawings were produced between 1908 and 1914 and are currently archived in the Jangseogak Royal Archives at the Academy of Korean Studies [
14].
Figure 6 lists the original drawings of these 15 cases in chronological order, and in this study, they were referred to as ‘hybrid roofs.’ Unfortunately, none of these 15 cases have survived to date, and all remain as drawings.
While examining the architectural drawings of these 15 cases of ‘hybrid roofs’, we were the most curious about why the inside (roof structure) and the outside (roof exterior) were so different. When we think of the design and construction of a building within the concept of so-called ‘architectural style’, the construction method and appearance are often closely interrelated—at least if it is pre-modern architecture—as the appearance is largely attributable to how the structure is formed. What makes these cases very interesting is that their construction methods are independent of appearance. From the outside, it seems to faithfully follow the traditional Korean architectural style, but the internal construction method is completely different as it is composed of a Western truss. Why did it have to be built in this way? Why and when did trusses come to be used for Korean-style roofs? What kind of transformation was drawn out from the truss that was used in these cases to realize the exterior form of a Korean-style roof? This study intends to answer these questions.
2. Materials and Methods
This study was conducted in the following order. First, 15 cases were analyzed by comparing Western-style truss roofs and Korean-style roofs through three perspectives—structural frame, roof curve, and eaves space—as a focus of analysis. Then, 15 drawings were reproduced in the form of color-coded analysis drawings, and the following steps of analysis included the examination of which construction method was used, what was different from the existing construction method, and where the transformation occurred. The last part of this study dealt with the periodic, historical context, their political implications, and their historical significance within the overall architectural history.
2.1. Analytic Framework
For these 15 cases, it is difficult to describe the common characteristics at a glance because the structure and appearance of a Korean-style roof, a Western-style truss roof, and sometimes a Japanese-style roof coexist. Most pre-modern buildings have sloped roofs, but the exterior and interior structures are significantly different depending on the culture and region. Let us take a look at the structure and appearance of the three roofs, respectively, and think about the correspondence and distinctiveness.
First, the roof of the Korean timber structure is composed of diagonal rafters placed above the framing with horizontal beams, short columns (
dongjaju), and purlins (the name and composition of each component are shown in
Figure 7). The Korean timber structure was derived from the Chinese one, which transfers the heavy load of the tiled roof to the structure underneath using beams, truss posts, and purlins without a truss or bracing. Since its establishment in the 5th century BC, it had not undergone significant changes for over 2000 years and remained dominant in Asia until modern Western architecture was introduced. [
15] Beams are the most critical structural members that transfer the roof’s load to columns, and their cross-sectional area is about two or three times larger than that of rafters. Rafters form the roof slope, and the inclination of long rafters and short rafters are made slightly different to adjust the roof’s height and width. Wooden plates cover the long and short rafters, and the layer of soil and wood is placed over the plates before laying the roof tiles, whose inclination is carefully adjusted. (
Figure 7) The difference between the inclination of long and short rafters sometimes becomes the basis for realizing the roof curve. Another quintessential characteristic of the traditional roof is the space under the eaves, as the eaves are notably protruded further from the columns. One end of the long rafters is placed over the middle purlin, and another end is protruded outwards as a cantilever. Sometimes, additional extension rafters called
buyeon are used to secure a larger space under the eaves.
Figure 8 shows a Western-style truss roof that appears in the case of Choongang High School, built in 1917. The horizontal members and the diagonal members are connected in a triangle shape, and unlike the Korean-style roof, the thickness of the members is constant because the load can be evenly distributed to each member. The diagonal member, called the top chord, is a single long member that determines the slope of the entire roof, and this slope is directly reflected on the exterior. A typical Western-style truss roof does not have the vast eaves space as that under a Korean-style roof. However, as shown in
Figure 9, there are cases where the top chord is pulled outward from the column, but it is different in shape from that of a Korean roof.
Figure 9 is a section drawing of the Korea Pavilion at the Tokyo Taisho Expo, which is one of the 15 cases that are highlighted in this study. It is interesting that the internal structure is made of a truss, but its exterior is curved in appearance. Instead of piling up the soil on the long and short rafters, the roof curve is realized by placing members of various heights on the top chord. When creating the eaves, it is different from the Western-style truss roof in
Figure 10 in that the diagonal members (the blue member in
Figure 9) are placed on the top chord. Rather, this method is quite similar to the form and building techniques of ‘
buyeon’ used in the Korean-style roof (the blue member in
Figure 7).
Based on the characteristics of the structure and appearance of Korean-style roofs and Western-style truss roofs, we will focus on the following three perspectives in analyzing the 15 cases that are the subject of this study:
Structural Frame—What kind of truss replaced the Korean-style roof structure? Are there any parts of the typical truss transformed? How and why do transformations occur primarily? This will be covered in detail in
Section 3.1.
Roof Curve—What building components were added to create the characteristic curve of the Korean-style roof? This will be covered in
Section 3.2.
Eaves space—What building components were used to create the eaves space? This will be covered in
Section 3.3.
2.2. Methodology: Creating Analytic Drawings
To analyze the 15 cases according to three features explained above (structural frame, eaves protrusion, roof curve, and eaves space), the original drawings were simplified and redrawn as a diagram in
Figure 11 with color-coding.
2.3. Background and Preceding Studies
The history of truss roofs in Korea began with the opening of ports at the end of the 19th century. The first building to use trusses on the roof was Beonsachang (Joseon’s weapon factory), built in 1884. From the end of the 19th century to the beginning of the 20th century, which was before the ‘manuals on modern building techniques’ were distributed by the Japanese, Western-style truss structures could mainly be found in religious buildings and consulate offices, designed and constructed by Westerners. A wooden king truss was used in ‘Yongsan Theological School’ built in 1892, a roof truss using both wood and iron was used for the first time in ‘Jeonggwanheon Hall’ of Deoksugung Palace (
Figure 4) built in 1900, and a wooden queen truss was used in ‘Choongang High School’ (
Figure 8) built in 1921 [
9].
Trusses have been actively used in Korea since the introduction of Western-style building techniques through the above-mentioned manuals during the Japanese Colonization period. Among the 1045 books on modern building techniques stored in the National Library of Korea, 16 books had the content of ‘Western-style wooden roof trusses.’ The truss types introduced in these manuals can be categorized into four: the king post truss, queen post truss, mansard, and compound truss (see in
Figure 12). Likewise, the ‘Western-style truss roof’ was introduced and used in Korea after already being reinterpreted by Japan, and therefore, attempts to improve traditional Korean wooden structures or infuse truss systems with traditional structures were quite limited [
18].
On the other hand, Japanese scholars tried to improve the traditional Japanese wooden structure, starting from the end of the 19th century. There was a debate among scholars about the strength and weakness of traditional structures and Western-style trusses, and efforts were made to improve the downside of traditional structures by applying Western-style trusses. For example, it was possible to increase the rigidity by using diagonal members such as braces, or to reduce the thickness of the timber by using metal joints instead of traditional wood joinery. This was also more favorable from the perspective of seismic design. Such an improved roof structure was referenced by practitioners through the 20th-century books on architectural techniques that were published later [
19].
As the 15 cases discussed in this study were also designed by the Japanese, they may have been influenced by the aforementioned Japanese manuals on modern building techniques. In particular, the
Improved Japanese House Structure published in 1919, the earliest among those books, introduces the Japanese wooden structure and construction methods of the Western truss (
Figure 13). Some of its figures show hybrid construction methods. In other words, a roofing method for a curved roof and eaves space while replacing the internal structure with a truss is introduced, presumably to realize the appearance of a Japanese roof (elevation drawings showing the finished appearance of the roof are not included in the book). The structural method used in the 15 cases studied in this paper is basically similar to this ‘hybrid’ method, but much more diverse variations are found. These variations are important clues that reflect what was deemed necessary to realize the appearance of a Korean roof, different from similar cases in Japan. It is necessary to pay attention to what kinds of changes were needed to shape the exterior of a Korean-style roof, how each component of the truss was segmented or transformed, and whether the influence of the traditional Korean wooden structure could be found in the transformation process.
5. Conclusions
This study analyzed 15 cases where trusses were used for a building with a Korean-style roof by scrutinizing architectural drawings produced during the Japanese Colonization period (1905–1940) in Korea. Their technical characteristics were interpreted to grasp the significance of these cases. They demonstrated the attempts to form the Korean-style roof with a smoothly curved, concave roof and eaves space by re-transforming the ‘Western–Japanese hybrid’ structure that Japan had created by introducing Western trusses in the early 20th century. These buildings are exemplary cases of showing multiple layers of hybridization, being designed by the Japanese, having an exterior of a Korean-style roof, and using the truss system for the roof structure. Situated in the margin of both Japanese and Korean architectural history, these are cases that have not been previously studied in depth.
Analyzing the architectural drawings from three points of view—structural frame, roof curve, and eaves space—proved that it was obvious that the truss was used to make the roof lighter, but what was more interesting was to observe the transformations of the truss to realize the appearance of a Korean-style roof. The top chord was segmented to create a smooth roof curve in some cases; the cantilever members were attached to secure an eaves space in other cases. However, the extent and category of such changes varied. These subtle changes reveal the limitations of the previous mainstream studies that argued the wooden roofs of East Asia have become lighter due to the ‘inflow’ of Western-style truss technologies. In other words, the architectural style and construction techniques of the modern Western countries, Japan, and Korea were intertwined and had a multi-directional influence on each other.
Another thing to note is that all of these cases were buildings constructed with a clear political purpose, built by Japan in the Korean palaces or for expositions to promote its imperial rule. The 11 cases built at the expo were each called ‘Korea Pavilion’, that is, buildings that exhibited the culture of the colonized country. Although the pavilion of its own country had a Western-style exterior, the ‘Korea Pavilion’ was to show the superiority of the colonists by faithfully replicating traditional Korean architecture—pre-modern architecture—to show the superiority of the colonists through a distinctive contrast. It is also noteworthy that even when having a Western-style, a Korean-style, or Japanese-style exterior, the basic structure was built with a truss, and some modifications were made to forge the exterior of an architectural style suitable for the purpose. These flexible adjustments can be seen as a ‘change to the modern era’, in which materials and construction methods (structural framework and construction principles) do not necessarily have a close relationship with the exterior (what is seen from outside).