Temple Roofs: Nihon Temple Architecture Roofs – Noyane
Noyane (Hidden Roof)1 is a type of roof widely used in Buddhist temples and Shinto shrines as part of Nihon Architecture. It is composed of a true roof above and a second roof beneath, permitting an outer roof of steep pitch to have eaves 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 Keshōyane (化粧屋根 ; cosmetic roof).
→ Structure of Noyane [Source: https://upload.wikimedia.org/wikipedia/commons/thumb/5/53/Noyane.svg/800px-Noyane.svg.png]
Its earliest extant example is Hōryū-ji's Daikō-dō, rebuilt after a fire in 990 CE.
→ Daikō-dō (Built 990 CE) of Hōryū-ji in Ikaruga-chō, Ikoma-gun, Nara Prefecture, Japan [Source: https://upload.wikimedia.org/wikipedia/commons/thumb/6/68/Horyu-ji40s3200.jpg/800px-Horyu-ji40s3200.jpg]
Development and Details
Till 8th century CE: Roof structures before Noyane
Nara period (710 CE – 794 CE)
During Nara period (710 CE – 794 CE), the structural elements of a roof were considered ornamental and therefore left exposed by design. The rafters supporting the roof's eaves 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 Hōryū-ji's kon-dō (5 -storied pagoda).
As the local climate is moister than in either Zhōngguó or Korea, roofs needed 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.
9th century CE onwards: Introduction and proliferation of Noyane
Heian period (794 CE – 1185 CE)
It was already observed that steeper roof and wider eaves required for local climate restricted light to the windows and trapped humidity. The solution devised by Nihon artisans was to construct a hidden roof raised above a ceiling which had non-structural rafters 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.
Noyane 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 in Mainland Asia. It was consequently extremely successful and widely adopted all over Nihon — one important exception is the architectural style called Daibutsuyō which, although arrived in Nihon from Zhōngguó at the end of 12th century CE, thus well after the invention of the hidden roof, never adopted it.
Influence over structures:
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: eg. Fuki-ji's Ō-dō has a square roof over a rectangular footprint. Ways were also found to make use of the space between the two roofs: eg. at Jōruri-ji in Kyōto (1107 CE) 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.
Influence over other architecture elements:
Before the invention of the hidden roof, the so-called tsumakazari (妻飾 ; gable ornaments) were simply structural elements left visible by design. After the adoption of the hidden roof, the tsumakazari remained in use, albeit with a purely decorative role.
→ Denpō-dō of Hōryū-ji — tsumakazari, which are all structural elements in this case, are visible within the gable. [Source: https://upload.wikimedia.org/wikipedia/commons/thumb/6/6b/Horyu-ji55n4500.jpg/1920px-Horyu-ji55n4500.jpg]
At the end of 10th century CE, the invention of noyane, which had its own hidden supporting structure, made the intercolumnar struts called Nakazonae2 unnecessary. They remained in use, albeit in a purely decorative role, and are typical of Wayō architecture style.
→ Types of Nakazonae [Source: https://en.wikipedia.org/wiki/Nakazonae]
https://en.wikipedia.org/wiki/Hidden_roof
https://en.wikipedia.org/wiki/Nakazonae