Irimoya (East Asian Hip-and-Gable Roof)

Irimoya (入母屋) is the Japanese name for the hip-and-gable roof, a roof that slopes down on all four sides like a hip roof but whose upper portion, on two opposite ends, is formed as a vertical gable. The resulting silhouette, with a triangular gable above a broad, sweeping hipped skirt, is one of the most recognisable forms in East Asian architecture. It is also called the "resting hill" roof, and in Japan moya-zukuri.

Regional names

• China: xieshan (歇山). Tradition credits its development, as an adaptation of the hip roof, to the Eastern Han dynasty.
• Korea: paljakjibung (팔작지붕). It was the most common roof type in authoritative buildings of the Joseon dynasty.
• Japan: irimoya, introduced from China in the 6th century.

Structure

In Japanese temple architecture the gable sits over the moya (the core of the building), while the lower hipped part covers the hisashi, the surrounding aisle or veranda. The arrangement allows a deep, sheltering eave all around the building while keeping the visual emphasis of a gable.

History and use in Japan

Irimoya roofs were first used for the main halls and lecture halls of Buddhist temple compounds. They were later adopted for the main sanctuaries (honden) of Shinto shrines and for palaces, castles and, during the Middle Ages, folk dwellings. They remain in wide use in temples and shrines. Examples include the Tamamushi Shrine, Shimogamo Shrine and the main gate of Shitennō-ji. Shikorobuki is recorded as a variant of the form.

Other notable examples

• The Great Buddha Hall of Nanchan Temple in China, dating from the Tang dynasty.
• Muryangsujeon Hall at Buseoksa temple in Korea.

Roofing materials

Irimoya roofs are covered with clay tiles, copper sheet, cypress bark, wooden shingles or thatch, depending on the building's rank and period. Ornamental ridge tiles and gable boards are characteristic.