Natural building, or eco building, involves the construction of wood ovens, shelters, barns, and even entire houses using sustainable materials and traditional building methods. While it has seen a recent surge in popularity and is seen as a ‘novel’ building method by many, natural building actually dates back to prehistoric times, and incorporates the same materials used in the construction of the oldest shelters that are in existence today. Eco building focuses on creating beautiful, environmentally sustainable homes that are strong enough to stand the test of time, and are created using materials that are usually sourced from the very site that the structure will stand on. Earth, clay, sand, stone, and straw are used in different combinations to form sturdy, breathable structures that provide healthy living environments with minimal damage to the environment.
Cob is one of the most popular methods of eco or sustainable building as the material can be sculpted into smooth, elegant shapes using only the hands, and many cob houses are inspired by the stunning Modernista buildings of Spanish architect Antoni Gaudi. Cob style is a mixture of clay, sandy subsoil, straw, and water, and forms a soft, pliable material that is extremely easy to work with, and is used to build interior and exterior walls that provide effective insulation against both hot and cold weather. Houses usually feature thatched roofs that must be effective at keeping rain from penetrating inside the walls, and the exterior is protected using earthen or lime plasters.
The first cob buildings are thought to be over 10,000 years old, and are still standing at Jericho in the West Bank. There are many cob houses scattered across England and Wales, and modern cob structures are beginning to receive artistic recognition. Cobtun House was built in 2001 and won the Royal Institute of British Architects’ Sustainable Building of the Year award in 2005. The home was designed and built for a retired lawyer by Associated Architects, and featured solar panels and a rooftop system to harvest rainwater. The renewed interest in cob has led to many enthusiasts offering cob building courses where participants learn to mix materials using the traditional method of the ‘cob dance’ which is similar to the Old World method of pressing grapes. They also learn how to build a cob structure from the foundation all the way up to the roof, and many have gone on to build their own homes using their new found talents.
Earthbag construction is a popular technique used in sustainable building that is regularly used as a method of flood-control, and evolved from the military bunkers that were constructed using sacks filled with earth or sand to provide protection and shelter. Modern earthbag construction typically uses whatever materials are available locally such as soil, crushed volcanic stone, gravel, and perlite. The material is then tightly packed into polypropylene bags which are stacked on top of each other to create, thick strong walls that are resistant to flood and earthquake damage. In the past, hemp or burlap sacks were used in traditional earthbag structures, but these materials are subject to rot and most builders now choose to work with polypropylene sacks which are much more durable. Two variations on this technique are superadobe, which uses bags filled with a mixture of sand, clay, and water, and rice-hull, which uses bags stuffed with raw rice-hulls.
The bags are held in place with lengths of barbed wire that is placed between each layer, or can be tied together using twine. The walls can be built in straight vertical stacks, or curved into a dome to form a structure that resembles an igloo or beehive. Once they are all in place, the structure is covered with either adobe, or some other form of natural plaster to protect against the elements and give the house a more modern aesthetic. This type of building is often used in disaster relief, and was the primary method of construction used to build homes for survivors of the 2004 Indian Ocean tsunami by charitable foundation, Builders Without Borders.
Adobe or Mudbrick
Adobe is an ancient sustainable eco building technique that combines a mixture of sand, clay, water and an organic material such as straw or water which is shaped into bricks and left to dry in the sun. It is thought to have originated from Egypt where the first adobe homes were built around 3800 B.C. It is most suitable to dry, hot climates that will allow the bricks to completely dry out, and adobe structures can be found in parts of Africa, Asia, South America, and Spain. Once dried, the bricks are incredibly strong and heavy, and adobe houses need tightly compressed earth foundations that will not settle and cause the bricks to crack. They offer great thermal advantages for hot climates by allowing the structure to ‘breath’, and adobe is still widely used in many parts of the world.
Mudbrick is a similar natural building technique which substitutes the use of clay for loam, which is a type of soil made up of sand, silt, and a small amount of clay, and the mixture is bound together using straw or rice-hulls. This composition works better in cooler climates and is used in modern structures throughout Britain and North America. The bricks are shaped and left to dry in the sun as with adobe, or if this is not possible they can be baked in a kiln. Once built, both adobe and mudbrick houses are finished with a plaster composed of the same mixture that was used to make the bricks.
Rammed earth is known by many names around the world, and the most famous example of this technique is the Great Wall of China. Rammed earth involves compressing a mixture of earth, gravel, chalk, and lime, using huge frames or molds to form entire walls at once. In ancient times it was extremely labor intensive as the compressing would need to be done using the hands or feet, but modern methods employ the use of machines in order to form walls or large building blocks. Rammed earth walls are considered to be thermally massive, which refers to their ability to resist outside temperature fluctuations and maintain a consistent indoor temperature. The technique can be used to build tall or monolithic structures, and is much faster than other earth building methods due to the fact that very little water is used in the mixture. Adobe and mudbricks generally need around 25 – 40 days to dry before they can be used, but rammed earth walls can be used immediately after forming.
Compressed Earth Block
Compressed earth blocks (CEB) are formed in a similar way to rammed earth walls, but the frames are much smaller and produce blocks that are usually the size of regular house bricks. Soil is packed into the frames and then compressed using either a hydraulic press, or by hand, and the mixture can be stabilized using a small amount of concrete or lime. Once dry, they are used to build walls in the same way as traditional masonry techniques, using a mortar comprised of the same mix used in their creation. Clay or sand can also be added to the mix to give extra strength or greater thermal mass.
CEB is the most widely accepted form of sustainable building, and many construction companies exist in various parts of the world that work exclusively with this method. Many new housing developments in Arizona are constructed from CEB, and the practice is spreading to neighboring states at an increasing rate. Due to its popularity, a CEB Code of Practice has been written regulating the use of the technique in the United States, and technological advances have led to the creation of better presses which create stronger, more durable blocks.
Eco building benefits the environment in a huge number of ways, and the most obvious is through the use of natural materials. Cement is one of the largest CO2 contributors in the world, and its production is responsible for around 5% of the entire planet’s CO2 emissions. In order to use it for building structures, it has to be transported to the construction site along with other building materials such as wood, bricks, glass, metal, and plastic. Transporting so many materials from various parts of the country requires the use of heavy duty vehicles that spew CO2 into the air and contribute greatly to the greenhouse effect. Sustainable building sources most of the materials used locally, and as most of the labor is performed by hand, there is no need for other environmentally harmful machinery such as diggers, cranes, cement mixers, and bulldozers.
As well as having clear advantages to the environment, sustainable building also benefits society by bringing people together in order to create structures that will provide shelter and warmth to those in need. There is a spiritual aspect to sustainable building which is often remarked upon by those who practice it, and many enjoy the feeling of connectedness that comes from many people working together towards a common goal. Building your home using your own two hands and with materials sourced from the earth is a profound experience, and those who have done it speak of how the process promotes a feeling of connectedness, both with the planet and with society as a whole.
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