Ancient Khmer Masonry at Phnom Bakheng

For almost 20 years I have worked on the conservation and restoration of Angkor monuments, and I have learned many things from the construction techniques of these Khmer monuments. Construction materials used for almost all the Khmer temples are basically the same, including sandstone, laterite, and bricks. However, the temples were built in different periods and styles, so the construction methods are different.

I am very interested in the method of terrace wall construction of Bakheng temple, WMF’s largest project in Cambodia at the moment. In order to build the walls of the temple, the sandstone was first cut into blocks and piled up from the lower layer to the upper layer. The lower layer of the wall was made of longer stones and the upper tier of shorter ones: the long and short bricks alternated on the whole vertical direction. The important thing is that the surface of the longer stones was slightly grooved before piling up the upper tier to prevent the stone from moving. The WMF team recently found the use of a very important technique called the mortise and tenon joint in some locations of the terrace wall of the Bakheng temple. The mortise and tenon is a key-lock that the ancient Khmer originally used for their wooden structures and that here they copied in stone. This technique was likely used in order to fix the position of thinner stone blocks that could easily fall off, and we found two types of it.

As we know, Bakheng temple was built in early 10th century under the reign of Yashovarman I and I can say the mortise and tenon joint is unique to this temple and I have never found it in any other temples built in later periods that I’ve worked on. After 20 years at Angkor, this is the first time I can see this very special construction method in Phnom Bakheng and it makes me want to do more research about it.