Once man began to settle, water became the key feature governing the generation of agglomerations of people - forming villages, towns and cities. All across the globe civilizations prospered along the riverbanks of the Nile (The Egyptian Civilization), the Tigris and Euphrates (the Sumerian or Mesopotamian Civilization), the Indus (the Harappan Civilization) and the Hwang Ho (the Hwang Ho Civilization).
STRUCTURES BUILT
The predominant structures built were:
- Houses predominated the cityscape. They were constructed using sun-dried bricks. The floors were usually packed earth. The construction is described below.
- The Temple was not a feature which occurred in all the civilizations.
- The Granary was the most important element of the city. This was the structure which held the food for the entire city. This was the wealth of the city and its livelihood. Usually the granary was built on the highest point of the city to provide some protection during the flooding season.
For the first time in the history of construction, a prefabricated unit was created - the sun-dried brick. This brick formed the module of construction in all the river valley civilizations. This brick was made from mud and straw. Straw and mud, abundantly found in the river flood plains, were mixed together. This wet mud and straw mixture was then formed in a four-sided wooden frame. After evaporation had hardened the mixture sufficiently, the form was removed. The bricks created thus, were then left in the sun to be dried completely. The straw acted as reinforcing to hold the mud together when evaporation caused inevitable shrinkage of the mud. Fired bricks, using the technique of kiln firing, were used later in Mesopotamia. But being more expensive in terms of labor and fuel, they were used for heavy use areas, like pavements and sewers.
CONSTRUCTION PRINCIPLES
The sun-dried bricks were laid in walls using wet mortar made of mud. Sometimes, bitumen was used as the mortar. Relying on the post and lintel principle, openings in the walls were supported by wooden lintels (refer The First Structures). (See Figure).
The climate being warm and dry primarily, the bricks could be left exposed most of the time. When needed, mud plaster was used. The roofs of these structures have not survived through all these millennia. But most likely there were constructed with wooden beams, and were flat. The flat roof was also suitable for the low rainfall climate in these river valleys.
STRUCTURAL FORMS DEVELOPED
With the use of a modular unit, it was easy to generate a corbelled arch. A corbelled arch is formed by placing one brick course over the other
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