building materials and methods

   The choice of materials for constructing houses, temples, and other structures in ancient Mesopotamia was dictated largely by the natural geology and topography of the area. The Mesopotamian plains were composed mostly of alluvial materials - silts and clays laid down by rivers and streams over the course of many millen-nia.Therewerefewtreesoroutcropsof stone from which to get suitable building materials, except on Mesopotamia's northern rim, in the foothills of the Zagros range and other mountain chains. Thus, the most common building materials by far in the region were clay and marsh reeds.

   Raw Materials The clay was used to make bricks. Some bricks were composed of clay only, but others contained a mix of clay and various binding materials, such as straw or sand, to add strength. The biblical book of Exodus (5.10-14) features a famous reference to the use of bricks containing straw. Typically the moist clay mixture was pressed into wooden or pottery molds, then deposited in rows on the ground to dry in the sun. The best time of the year for making sun-dried bricks was during the heat of summer. In fact, the first month of summer came to be known as "the month of bricks." Bricks were also sometimes fired in kilns, which made them harder and longer lasting. However, partly because of the scarcity of wood to fuel the kilns, fired bricks were more expensive, so they were used mainly for prestigious structures such as palaces. The earliest bricks used in Mesopotamia before circa 3500 b.c. were long and thin. By the late fourth millennium b.c., however, a standard brick with a length twice its width had evolved. Later the Akkadians developed a square brick measuring about 14 inches (35cm) on a side. Another popular variation that developed was a brick with one end that was convex (outwardly curved), which produced a variegated (motley), three-dimensional exterior surface.

   When building with brick, workers usually employed some kind of mortar. one common kind was a plaster made by mixing moist mud with powdered lime. Bitumen, a tarlike, petroleum-based substance, was also used for mortar and had the added benefit of being more or less waterproof. Abundant in what is now Iraq, the bitumen came from sticky deposits that formed at ground level in certain areas. Still, no matter what kind of mortar was used, sun-dried clay bricks disintegrated rapidly, necessitating frequent repairs. often houses and other structures became so dilapidated that people simply leveled them and built over them. These new structures also decayed, and slowly but steadily cities came to rest on mounds of debris from past ages. When the cities were eventually abandoned, the still-disintegrating mounds became known as "tells."

   Whenever possible, roofs and doorways in the newer structures were made of wood or stone. The cheapest, softest wood came from the date palm, which was native to Mesopotamia. Or if the builders could afford it, they imported hardwoods from cedars and other trees that were plentiful in Syria and Palestine. Small timbers were used to frame doors or windows. Sometimes the upright supports, or posts, of the frame were wood, but the horizontal piece at the top, called a lintel, was a slab of stone. This was one of the few uses for stone in building, the others being bridges and canals. Because they had some access to stone from the mountains north of their homeland, the Assyrians sometimes used stone for the foundations and lower courses of the walls of some structures.

   Methods Most bricks and stone blocks were simply stacked, one on top another, in Mesopotamian structures. However, the arch was occasionally used, though not nearly to the extent the Romans later used it. Mesopotamian builders used both corbelled and true arches. As explained by L. Sprague de Camp in his classic book about ancient builders:

   Corbelling is laying courses or layers of stone or brick so that each course overhangs the one below. When walls are corbelled out from two sides until they meet, a corbelled arch or vault results. Although a structure of this kind is [not as strong] as a true arch, it is easy to make. (The Ancient Engineers,p.26)

   Whether or not arches were employed in them, large-scale structures often featured commemorative inscriptions by the builders. Carved onto stone or metal tablets, these sometimes consisted simply of the builder's name and perhaps the date. Others consisted of short or long messages. It was common to urge future kings and builders to treat the structure with respect, and sometimes the builder placed a written curse on any and all who might not do so. The inscribed tablets were placed in a box and buried beneath the foundation or were inserted into spaces between the wall bricks.

   Though brick structures were erected in many parts of Mesopotamia, in the marshy regions, by contrast, excessive water and moisture made building with clay bricks impractical. So most people who lived in the swampy lowlands near some of the rivers - especially in the region lying northwest of the Persian Gulf - used marsh reeds for their houses. The chief method of erecting such structures was to tie clusters of tall reeds into thick, sturdy bundles and then dig holes and sink the ends of the bundles into the ground. The bundles, which stood upright like columns, were bent over and their tops were attached to the tops of other bundles, forming rounded arches. Crosspieces, also made of bundled reeds, connected and braced the arches, after which thick reed mats were tied to the top and sides, forming the structure's roof and walls. The light, narrow boats these marsh dwellers used to catch fish and water foul were also made of reeds.

   See also: bridges; houses; palaces; temples; ziggurat