The use of earth in the construction methods and materials started over 10000 years ago. Since that time, architects and constructors worldwide find new approaches for using this sustainable component in current building projects, enhancing its qualities. The soil building materials are appreciated for their thermal mass properties, durability, low cost and availability. Depending on geographical location, the soil has its peculiarities and variety of components.
People have used soil for construction purposes for thousands of years. The most ancient city recorded, Jericho, was built of earth. Ancient civilizations built houses, temples, mosques, and churches of mud bricks and rammed earth.
Today, numerous innovative projects actively employ ecological materials in construction. Adopting ancient soil building techniques and materials to modern construction demands provides an opportunity to create sustainable, efficient, and aesthetic solutions.
Types of soil buildings
Cob is one of the oldest and simplest earth-building technologies. Taos Pueblo in New Mexico is a cob construction and the most ancient continuously occupied dwelling in North America, the building of which is dated between 1000 and 1450. Cob is a technique of layering a combination of clay-rich soil, sand, straw, and water and compressing to form a structure. Cob houses have thick walls with the gradual thinning to the top. The porous cob structure makes it durable and resistant to the rains. Cob is a low-cost material but somewhat labor-intensive, which makes the building process slow.
Adobe structures have been used since about 5000 BC in Egypt and the Near East and continue to be used in modern construction. Adobe is a mixture of thick mud and straw shaped manually or in wooden molds. The size of adobe bricks may vary depending on the area and soil structure used for it. The term ‘adobe’ indicates the bricks, the mortar, and the soil plaster covering it. Adobe material has a high thermal mass, durable, solid, and suitable for most types of buildings. Building with adobe bricks is more time-consuming in comparison to other earth construction methods. The thick walls of adobe buildings reduce the ratio between the total building space and usable interior space.
Superadobe is a construction method of using sandbags with soil developed by Iranian architect Nader Khalili. The soil in the handbags is arranged in layers with barbed wires between these layers forming reinforcement and mortar. The interest in superadobe technology is constantly growing these days with such buildings becoming common in Canada, Mexico, Thailand, Chile, India, Iran, Siberia. The method is most suitable for building domes, arches, and vaults.
Rammed-earth structures are created from damp soil tamped between shutters using rammers. Sand, as well as cement, may be added to the mixture for additional strength and durability. Using packed mud in construction is a technique that originated about 10000 years ago and has been used on five continents. Among the most famous examples of the rammed-earth structures are the Great Wall of China, Teotihuacan in Mexico, Alhambra in Spain. This type of construction is still practiced worldwide to create beautiful buildings and remains suitable for different climates. Rammed-earth structures are appropriate for building load-bearing and free-standing columns.
Poured-earth is a technique of pouring soil with low clay content into a framework, which is quite similar to concrete production using gravel. High water content is considered one of the disadvantages of the technology as it often results in shrinkage after drying.