Rammed earth

Historic and vernacular, such as found in Morocco and the Himalayas

To construct a rammed earth wall, a formwork box is constructed using two parallel timber sides, supported on two or more horizontal timbers. Vertical timbers are then placed through holes in the ends of the horizontal timbers thereby restraining the formwork. These vertical timbers are connected at the top using rope, forming an open box.

Soil is taken from the ground and if necessary sieved to remove larger particles. Additives such as straw or lime may be mixed into the soil, which is then dropped into the formwork in layers, usually around 150mm high. The layer is then compacted using a heavy rammer. Upon compaction of one layer, another layer of earth is placed in the formwork and the process repeated until the formwork is full.

The formwork is then removed and placed on the next set of horizontal timbers where the process is repeated. Once the formwork has been moved on, the horizontal timbers are removed from the wall leaving characteristic holes. Upon completion of one horizontal level the formwork is moved vertically, the mass of standing wall being known as a lift. A rammed earth wall can thus be constructed using very little manpower and crucially without recourse to temporary works such as external scaffolding.

Modern rammed earth

Modern rammed earth building has recently become popular because of its sustainable credentials. In parts of North America, Australia and New Zealand, cement stabilised rammed earth is becoming a popular building material. In Europe, unstabilised rammed earth is seen as a very 'green' building material. Modern rammed earth construction uses formwork similar to that of concrete, and electric or pneumatic rammers are used.