The Also sometimes called . ''Koya'' is the technical term for the space between the roof and the ceiling. is a type of roof widely used in Japan both at

Buddhist temples A Buddhist temple or Buddhist monastery is the place of worship for Buddhists, the followers of Buddhism. They include the structures called vihara, chaitya, stupa, wat and pagoda in different regions and languages. Temples in Buddhism represen ...

and

Shinto shrines A is a structure whose main purpose is to house ("enshrine") one or more '' kami'', the deities of the Shinto religion. Overview Structurally, a Shinto shrine typically comprises several buildings. The ''honden''Also called (本殿, meani ...

. It is composed of a true roof above and a second roof beneath, permitting an outer roof of steep pitch to have

eaves The eaves are the edges of the roof which overhang the face of a wall and, normally, project beyond the side of a building. The eaves form an overhang to throw water clear of the walls and may be highly decorated as part of an architectural styl ...

of shallow pitch, jutting widely from the walls but without overhanging them. The second roof is visible only from under the eaves and is therefore called a "hidden roof" (giving its name to the whole structure) while the first roof is externally visible and is called an "exposed roof" in English and in Japanese. Invented in Japan during the 10th century, its earliest extant example is

Hōryū-ji is a Buddhist temple that was once one of the powerful Seven Great Temples, in Ikaruga, Nara Prefecture, Japan. Its full name is , or Learning Temple of the Flourishing Law, the complex serving as both a seminary and monastery. The temple was ...

's Daikō-

dō Dō may refer to: * Dō (architecture) * Dō (armour) * Dō (martial arts) * Dō (philosophy) ''Tao'' or ''Dao'' is the natural order of the universe, whose character one's intuition must discern to realize the potential for individual wisdom, ...

, rebuilt after a fire in 990.

History and structure

Japanese architecture has been typified by wooden structures, elevated slightly off the ground, with tiled or thatched roofs. Sliding doors (''fusuma'') and other traditional partitions were used in place of walls, allowing the internal configuration of a space to ...

continued to evolve after new techniques imported from China and Korea together with Buddhism around the 6th century. Climate in Japan being different from that on the continent, several structural adaptations became necessary, the most important of which is the ''noyane'', invented some time during the Heian period (794–1185). During the previous

Nara period The of the history of Japan covers the years from CE 710 to 794. Empress Genmei established the capital of Heijō-kyō (present-day Nara). Except for a five-year period (740–745), when the capital was briefly moved again, it remained the c ...

(710–794), the structural elements of a roof were considered ornamental and therefore left exposed by design. The rafters supporting the roof's

would enter the building and would then be visible from below. Above the rafters would be laid directly on the roofing material, for example wood shingles. This is the structure of

's '' kon-dō'' or five-storied pagoda. Because the local climate is more moist than in either China or Korea, roofs had to have a steeper incline to help quicken the flow of rainwater. Due to the permeable nature of the walls, and the lack of channelled roof drainage, it was necessary that eaves project far from the walls. On a roof of steep pitch, the wide eaves were also deep, restricting light to the windows and trapping humidity. The solution devised by Japanese artisans was to construct a hidden roof raised above a ceiling which had non-structural

rafter A rafter is one of a series of sloped structural members such as wooden beams that extend from the ridge or hip to the wall plate, downslope perimeter or eave, and that are designed to support the roof shingles, roof deck and its associate ...

s as aesthetic elements. From the hidden roof projected the principal rafters of the shallow-pitched eaves. The structural elements of the outer roof were raised above this, with an outer inclination completely independent of the pitch of the eaves. The earliest extant example of hidden roof is Hōryū-ji's Daikō-dō, built in 990 and was discovered only in the 1930s during repair work.

Influence

This structure not only solved drainage problems, but eliminated deep shadows and gave the whole temple a feel that was very different from that of its ancestors of the Asian continent. It was as a consequence extremely successful and was widely adopted all over the country. One important exception is the architectural style called Daibutsuyō which, although arrived in Japan from China at the end of the 12th century, thus well after the invention of the hidden roof, never adopted it. Also, although all extant

Zen Zen ( zh, t=禪, p=Chán; ja, text= 禅, translit=zen; ko, text=선, translit=Seon; vi, text=Thiền) is a school of Mahayana Buddhism that originated in China during the Tang dynasty, known as the Chan School (''Chánzong'' 禪宗), and ...

temples have it, it is likely that the

Zenshūyō is a Japanese Buddhist architectural style derived from Chinese Song Dynasty architecture. Named after the Zen sect of Buddhism which brought it to Japan, it emerged in the late 12th or early 13th century. Together with Wayō and Daibutsuyō ...

style, which arrived roughly at the same time of the Daibutsuyō, adopted the hidden roof only some time after its arrival. Because the hidden roof allowed the structure of the roof to be changed at will with no impact on the underlying building, its use gave birth to many structural innovations. For example, Fuki-ji's Ō-

has a square roof over a rectangular footprint. Ways were also found to make use of the space between the two roofs. For example, at Jōruri-ji in Kyōto (1107) part of the Hon-dō's ceiling was raised above the rest to give space to the room. Later it would become common to raise the exposed roof above the entire core of a temple building. The same evolution we have seen in Buddhist architecture can be seen in the roofs of several Shinto architectural styles it influenced. The kasuga-zukuri,

nagare-zukuri The or is a traditional Shinto shrine architectural style characterized by a very asymmetrical gabled roof () projecting outwards on one of the non-gabled sides, above the main entrance, to form a portico (see photo).

hachiman-zukuri The is a traditional Japanese architectural style used at Hachiman shrines in which two parallel structures with gabled roofs are interconnected on the non-gabled side, forming one building which, when seen from the side, gives the impression of ...

, hie-zukuri all followed the evolution path we have seen. All extant examples of the ancient

shinmei-zukuri is an ancient Japanese architectural style typical of Ise Grand Shrine's ''honden'', the holiest of Shinto shrines.Encyclopedia of Shinto It is most common in Mie Prefecture.JAANUS History Ancient shrines were constructed according to the style ...

taisha-zukuri Kamosu Jinja's ''honden'' and a granary at Toro is an ancient Japanese architectural style and the oldest Shinto shrine architectural style. Named after Izumo Taisha's ''honden'' (sanctuary), like Ise Grand Shrine's ''shinmei-zukuri'' styl ...

and

sumiyoshi-zukuri is an ancient Japanese Shinto shrine architectural style which takes its name from Sumiyoshi Taisha's ''honden'' in Ōsaka. As in the case of the '' taisha-zukuri'' and '' shinmei-zukuri'' styles, its birth predates the arrival of Buddhism in Jap ...

styles however show no sign of a hidden roof.

Tsumakazari

Before the invention of the hidden roof the so-called were simply structural elements left visible by design. See for example

's Denpō-dō in the photo to the right, where the brown elements within the gable are all part of the roof's support system. After the adoption of the hidden roof, the ''tsumakazari'' remained in use, albeit with a purely decorative role.

Nakazonae

Another of the repercussions of the invention of the hidden roof was the role change undergone by struts called . Nakazonae are intercolumnar

strut A strut is a structural component commonly found in engineering, aeronautics, architecture and anatomy. Struts generally work by resisting longitudinal compression, but they may also serve in tension. Human anatomy Part of the functionality o ...

s provided in the intervals between bracket complexes ('' tokyō'') at religious buildings in Japan. In origin they were necessary to support the roof above, however at the end of the 10th century the invention of the hidden roof, which had its own hidden supporting structure, made them superfluous. They remained in use, albeit in a purely decorative role, assuming a variety of forms, and are typical of the

Wayō is a Buddhist architectural style developed in Japan before the Kamakura period (1185－1333), and is one of the important Buddhist architectural styles in Japan along with '' Daibutsuyō'' and the ''Zenshūyō'', which were developed based on ...

style.

Notes

References