Chaitya Vault

A chaitya vault is the tall, round-topped ceiling of a chaitya hall, the Buddhist prayer hall of ancient India that holds a stupa at its far end. Almost every surviving example is cut into living rock in the hills of western India. Its main interest for roofing history is that it is a fossil of a vanished roof: carvers in stone copied, rib for rib, the bent timber and thatch roofs of free-standing halls that have not survived.

A roof copied in stone

Scholars agree that the form follows earlier halls built of wood and plant materials, none of which survive. The ceiling is a barrel vault, often slightly stilted so that it is taller than a true half-circle, with curved ribs running across it like the rafters of a timber roof. In the earliest halls real wooden ribs were fixed to the underside of the stone vault even though they carry no load; in later halls the ribs were carved from the rock itself. The front of the hall carries a large horseshoe-shaped window, the chaitya arch (also called gavaksha or chandrashala), which echoes the curved end of the roof and became one of the most repeated ornaments in Indian architecture.

Writers have long noted a broad likeness between the chaitya profile and the arched wicker roofs of the huts of the Toda people of the Nilgiri hills, and with the pointed, ridged barrel roofs of 4th-century BCE Lycian tombs in Anatolia.

Key examples

• Barabar Caves, Bihar (3rd century BCE, reign of Ashoka): the Lomas Rishi and Sudama caves are the earliest surviving spaces comparable to a chaitya hall.
• Bhaja, Maharashtra (2nd century BCE): possibly the earliest surviving chaitya hall, with a barrel-vaulted ceiling into which ancient wooden ribs are set.
• Karla, Maharashtra (about 50-70 CE, dated by donor inscriptions): the Great Chaitya is about 45 m (148 ft) long and up to about 14 m (46 ft) high. Its vault is lined with wooden ribs that are probably as old as the excavation, which would make them roughly 1,900 to 2,000 years old. A wooden umbrella over the stupa and a wooden frame inside the great arched window also survive.
• Kanheri Cave 3, near Mumbai: much of the timber in the roof is original, with some pieces replaced in the British period.
• Ajanta, Maharashtra: the later chaitya halls, such as Cave 19 (about 475-500 CE), repeat the chaitya arch many times on their facades.
• Ellora Cave 10, Maharashtra (first half of the 7th century): generally regarded as the last rock-cut chaitya hall.

Why it matters

Because timber and thatch decay, the rock-cut halls are the best evidence of how large public roofs were framed in India before about the 3rd century CE. They show curved rafters, a ridge and gable-end arches already in use more than two thousand years ago.