What Is Rammed Earth?
Rammed earth is an ancient building technique in which moist earth is compacted to the point that it forms a material similar to sedimentary rock (rock composed of sand, silt, clay, gravel, mud, and other material). Forms (wooden boards that define a specific area) are used to shape rammed earth into bricks or entire walls.
Rammed earth was used in structures dating back to 7000 B.C. It comprises portions of the 2,000-year-old Great Wall of China, as well as temples in Mali and in Morocco. Romans and Phoenicians (residents of the ancient kingdom of Phoenicia on the Mediterranean Sea) introduced the technique to the Europeans. It became a popular building technique in France, where it was known as pise de terre. In the United States it was used in the construction of elaborate Victorian homes, as well as in low-cost housing.
Today builders add cement to rammed earth, which results in stronger, waterproof walls. In traditional rammed-earth construction, hand or power tools are used to compact a mixture of moistened earth and cement between double-sided wooden forms to about 60 percent of the mixture's original volume. In a newer technique, a high-pressure hose sprays the mixture against a single-sided form. In some construction projects, steel reinforcing bars are also used.
Sources: Harrowsmith Country Life, vol. 9, no. 52 (July-August 1994), pp. 22-31; U.S. Department of Agriculture. Farmers' Bulletin no. 1500, pp. 1-3.