Building with adobe — a material created by mixing clay-rich soil with straw, sand, and other organic materials — has been in use since 8300 BC. It is popular in arid and semiarid places where wood is scarce. The word “Adobe” derives from the Arabic “al ṭūb” meaning “the bricks.” Adobe buildings are low energy, fireproof, biodegradable and durable if constructed properly. About a third of the global population still uses earthen structures today, especially in developing countries. This is sustainable because the materials have low embodied energy, are locally abundant, and can create energy-efficient buildings.
The ideal soil is usually found just below the ground’s top layer and becomes molded together with a little water. A small amount of dry material, such as straw or grass, is used as a binding agent; too much or too little can reduce the strength of the adobe structure. The dry materials counteract the cracking that occurs in the brick as it dries and shrinks. The amount of water in the brick is carefully controlled — too much can make the adobe unstable. The mixture is placed in a wooden form and leveled off, taking the shape of the form’s mold. The bricks are removed and placed on a level surface to dry for several days, followed by several weeks of air-curing. The resulting adobe bricks never get fired in a kiln so they are not waterproof.
Adobe houses are usually built on a solid foundation, constructed from stone, cement, or even seashells. Builders erect adobe walls by stacking the bricks on top of each other, using the same adobe soil mix as a mortar. To support the roof’s weight, the adobe walls must be thick. One study confirmed the thermal stability in adobe walls 50-cm (20 inches) thick, which is considered the standard width of earthen homes in Cyprus where adobe dates back to the Neolithic era.
The flooring of an adobe house can be similar to a modern home. Hardwood, flagstone, and tile are options, as well as adobe or fired brick. Historically, in dry environments where wood was scarce and adobe popular, vaulted or domed brick roofs were used. In southwestern North America in the 17th century, slightly sloped flat roofs with parapet walls were customary, built using logs covered with twigs or fabric and then adobe mud. In the 19th and 20th centuries, gable and hipped roofs became popular and, later, terra cotta and sheet metal.
Mud plaster created by mixing clay, sand, water, and a dry material is often applied to the exterior of the adobe house for additional protection from the elements. An enduring adobe home requires periodic maintenance. Adobe roofs and walls are prone to damage over time, usually due to water-related problems. More structural damage can occur if the adobe house was built incorrectly. Deterioration or damages can be repaired by patching or replacing the compromised adobe with new brick of as similar an adobe mixture as possible.
Due to its earthen makeup, adobe walls have a high thermal mass and are able to absorb heat throughout the day to keep the house cool while the sun is up, releasing the heat slowly at night to warm the interior. This process keeps energy consumption low in hot, dry environments. One study described the thermal inertia of adobe walls as a main contributor to the delay of heat transmission. The thermal mass of adobe ensures that the interior of the home remains relatively stable, slowing the changes during extremely cold or hot exterior temperatures. Adobe blocks do not insulate well in colder climates.
The natural material used in adobe significantly lowers the net energy consumption and waste production of the structure. One study found that 370 gigajoules of energy is conserved and 101 tons of CO2 is diverted each year using adobe. One gigajoule is equal to 277.8 kilowatt hours, or the equivalent of keeping a 60-watt bulb on for six months.
Compared to modern building materials, adobe bricks produce minimal total waste and zero hazardous waste. In the entire cycle of an adobe house’s life, the footprint on the environment is small. When materials are harvested from the local environment, transportation energy decreases significantly.
Other benefits to adobe include low sound transmission and the ability for homeowners to have an integral role in building their home due to the method’s simplicity. Moreover, an adobe house is very customizable in terms of design, and expensive construction equipment is minimized.
Adobe has regained popularity in recent years as a conservation method for and sustainable alternative to traditional homes. Location should be taken into account when considering this building method, as well as the upkeep required to ensure the adobe home remains in stable condition for the future. Its environmental efficiencies make adobe a good building option for those living in dry climates.
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