[CONSTRUCTION TECHNIQUES IN SOUTH AND SOUTHEAST ASIS] by JACOUES DUMARCAY
I extracted these from above book, which was written about Khmer stone architecture.
Sandstone is a stone with distinct beds. It was often extracted near the construction site. The block of stone was first outlined by a thin ditch cut out with an axhammer and then removed following the line of the bed. This method was also used in Southeast Asia, in particular amongst the Khmers. It is likely that the recommendations of the Mayamata that we mentioned above were used for sandstone. Once removed from its bed， sandstone loses the water that it contains due to evaporation. It brings to the surface a part of the cement that binds together the grains that make up the stone. This cement is left on the surface of the block and forms a hard crust after a month or two. Therefore，stonecutters must cut and sculpt the stone as quickly as possible once it is removed. This is quite inconvenient as if the stonecutters wait too long to sculpt， not only win the hard crust be difficult to cut， but it win also be destroyed. This crust win not reform if the evaporation is completed， which is particularly obvious when the stone is reused. As the reshaping destroyed the protective crust， erosion is quick to follow and particularly destructive. Builders extracted laterite using a process very similar to that used for the extraction of sandstone. However the ditches encircling the blocks were made with the sole tool of the quarrymen. This resembled an axe with a handle measuring 1.20 metres in length. The other side of the blade featured a sturdy head (Ph. 42). After being traced out， the block was removed using this same tool. This left a stair-shaped cut on the face， used to limit the tracing to two sole ditches (Ph. 43). This form of quarry operation spread throughout an of southern Asia， and particularly in Cambodia.
The most interesting borrowed technique was that of the forced chocks. From the middle of the 9th century onwards， the Khmer master builders made excellent use of this as can be seen， for example, in the construction of the pyramid of Phimeanakas in Angkor.
The Khmers seldom used collected stones. The stones of Vat Phu were used simply because the site was located at the foot of a cliff. Construction stones in Cambodia are extracted. There are many sandstone quarries on the Kulen plateau or in the surroundings of certain temples such as Beng Melea. Sandstone of many qualities was used，principally arenite for the great temple of Angkor Wat， for example，but also harder sandstone such as greywacke for the temple of Ta Kev (greywacke quarries have still not been discovered). Apart from sandstone, laterite was also used and extracted. A large quarry was discovered near the temple of Bantay Srei of which the working face measured about 3 kilometres. There is no difference in the cutting technique between laterite and sandstone. However， taking into account the formation of a crust due to the evaporation of water of the quarry for the sandstone， there is a major difference in their use. While， for laterite, it is easy to make a stock of stones ready for use， the same cannot be said of sandstone. Sandstone must be used as rapidly as possible and its reuse is almost impossible for sidings. This fact was forgotten by the Khmers at the end of the 13th century. We can see numerous restorations with reused stones， which had disastrous results for buildings on which the protruding surfaces quickly eroded away. This can be seen in the last operations of the terrace of the Leper King or on the reliefs of the north-east corner of the gallery of the first floor of Angkor Wat. These reliefs were sculpted in the 16th century on a wall built in the 12th century. In other words, the sculptors had a harder time finishing their work and they destroyed the protective crust that could not be reformed as the quarry water had already evaporated. As a result， the work quickly eroded.
The corbels that cover the galleries of Angkor Wat feature a particular stereotomy. Each element of the roofing is cut in a double right angle whose planes are tilted towards the exterior (fig. 84). This ensured，on the one hand， better coherence to the structure and on the other hand， the runoff of part of the rainwater caught in the vault. This technique has its disadvantages as the slightest movements of the structure deform the corbels. The implementation of the vault was effected from two sides of the sections (the great length of the galleries made this first operation necessary: the division of the vault into sections) by reversing the direction of the stones at right angles， which at the point where they came together， were blocked in place by a keystone. The use of wedges gradually dropped out of use， which can be seen in Cambodia in the Bayon (early 13th century) where the stereotomy is rather consistent. However, it seems that all the teams working on this prestigious worksite did not use the technique. For example，on the southern wall of the first gallery， the work was divided into different panels. On some， wedges were used judiciously， whereas on others， they weren't used at all.
Master builders in all climates have always aimed to harmonise the inner and outer appearance of the structure. Usually， between the aspect of the intrados of a vault or that of an interior chimney of a temple and their outer appearance， there are two views which seem irreconcilable. The master builders attempted to correct this difference. The simplest and most widely used solution involved setting a ceiling in the interior space， thus removing the appearance of the chimney of the intrados. This form was used all throughout southern Asia. The trace of one of the oldest ceilings can be seen in Sambor Prei Kuk in Cambodia (Ph. 35) in the octagonal towers. Sandstone hooks inserted in the brick walls of the towers supported a ceiling.