Khmer Corbel Vault

Khmer corbel vaulting is the method used by the builders of the Angkorian empire (9th-15th centuries, in present-day Cambodia and neighbouring countries) to roof stone and brick temples without a true arch. Each course of masonry projects a little further inward than the one below, until the two sides meet at the top and can be closed with a capstone.

How it works

In a true arch, wedge-shaped stones push sideways against each other and transfer load around a curve. In a corbel vault the stones are laid flat; each is held in place by the weight of the masonry above its inner end. The result looks like a pointed or stepped vault from inside, but it is structurally a pair of cantilevers. Khmer builders used the same principle for doorways, passages, galleries and the hollow interiors of towers, and used lintels for other openings.

Materials

• Brick in the earliest Angkorian temples, such as Preah Ko, Lolei and Bakong (dedicated 881).
• Sandstone from the Kulen hills, at first only for door frames and details; Ta Keo, in the 10th century, was the first temple built almost entirely of sandstone.
• Laterite for foundations and concealed parts.

Limitations

Corbelling is weaker than the true arch and limits how wide a stone-roofed space can be. Khmer galleries are therefore long and narrow. Galleries developed in the 10th century from hallways around the central sanctuary; in the Angkor Wat period (first half of the 12th century) half-galleries were added along one side to buttress the structure.

Corbelled roofs are also prone to collapse once maintenance stops, a central conservation problem at Angkor today. Where a wider room was needed, builders often topped stone walls with a light timber roof instead. The late 12th-century "halls of dancers" at Ta Prohm, Preah Khan and Banteay Kdei had such perishable roofs; only their walls survive.

Timber roofs beside the stone

Most Angkorian buildings were timber and have vanished. A 13th-century Chinese visitor described palace buildings with lead-tiled roofs, and reliefs at the Bayon and Banteay Chhmar show gabled and double-tiered timber roofs. These forms continue in the tiled pagoda and palace roofs of modern Cambodia.