Earth Building is the practice of building using unfired earth material. Earth is used to construct walls, floors, roofs and even furniture, fireplaces and ovens. It is a building technology with an 11,000-year-old history and tradition, which is utilised worldwide. Today it is estimated that between one third to one half of the world’s population are housed in earth homes.
The common feature in all earth building techniques is that the earth material is subsoil that is composed of clay, silt, and sand where clay is the binder or cementing ingredient and that the drying process is through the evaporative effect of sun drying.
The methods and techniques used are as varied as the people of the earth, the resources available to them and the climates in which they are used.
There are at least 12 methods of earth building used and these can be further divided into a total of at least 18 techniques.
Perhaps the best known methods are:
- Earth Brick (Mudbrick/Adobe)
- Mud brick is the most popular name used in Australia to describe bricks made from various compositions of soil and dried at air temperature in the brick production stage.
- No one really knows the earliest uses of mudbrick in the world but the oldest surviving bricks are 10,000 years old and mudbrick was one of the earliest building materials.
In Australia mudbrick was one of the many forms of earth building used by the early settlers and it is not unusual to find examples still in use which are over a hundred years old. The length of time some of these buildings have survived is remarkable considering the lack of good quality building practices that only came into general use in the middle of the last century.
- There are almost as many ways of making mud bricks as there are mud brick makers. One major distinction however is the consistency and water content of the material at the time of forming into bricks. With puddled mud bricks, the moisture content is quite high and the texture is that of mud or dough.
- Rammed Earth (Pise)
- Rammed Earth, also known as Pise’, uses in-organic earth material that is only worked when damp or moist, with or without any stabilising additive. Utilizing formwork panels, the earth mix is then rammed (tamped) in-situ to construct the wall structure. It is a solid masonry wall which does not have, or need, any cavity. Rammed Earth walls in Australia are generally 300mm thick, are cement stabilised with 5% to 10% cement. Rammed Earth walls are dense, stone hard and are commonly used as load bearing wall for single and double storey constructions.
Rammed Earth has been used in most parts of the world for centuries for every imaginable type of building. Rammed Earth has been used in Australia from the earliest historical days of English settlement and is currently in widespread use throughout Australia.
- Australia leads the world in modern Rammed Earth construction, both in quality and volume of projects built. Modern Rammed Earth grew to popularity in Western Australia, originally centred in the Margaret River area in the south-west of WA and now been widely adopted throughout all of Australia for home dwellings as well many public buildings.
- Cob is a natural building material used for constructing walls, it is a similar material to adobe mud brick. Cob walls are made from a mixture of mud, (sand and clays) and a fibrous organic matter with an acceptable tensile strength, like hay or straw, that is mixed together with water to create a mud pulp dough. Instead of casting the mixture into moulds to make individual bricks that are then later laid, cob walls are built by scooping up the mixture by hand and applying the pulp mixture directly to the wall in a freeform sculptural fashion, and hence, the walls are simply built in-situ from the footings upward.
- In recent times in Australia, cob has been growing in popularity, especially among the natural building and permaculture fraternity.
- Pressed Earth Brick/Block
A Pressed Earth Block (CEB), also known as a Compressed Earth Block, is a building material made primarily from an appropriate mix of fairly dry inorganic subsoil, non-expansive clay, sand, and aggregate. Making compressed earth blocks requires dampening the earth and mechanically pressing at high pressure in a mould, and then setting side the produced bricks to dry naturally. If the blocks are stabilized with a chemical binder such as Portland cement, they are called Compressed Stabilized Earth Block (CSEB). Typically, a compression of around 3,000 psi (21 MPa) is applied to the mix to create the brick with comparable compressive strengths to that of concrete blocks.
Creating CEBs differs from Rammed Earth in that RE uses a larger wall formwork into which earth tamped down, creating a whole wall in-situ at one time, rather than laying brick or blocks. CEBs differ from mud bricks in that the Mud Bricks are not compressed. The compression strength of properly made CEB usually exceeds that of typical mud brick. Various types of CEB production machines exist, ranging from manually hand operated such as a Cinva Ram to fully automated engine powered hydraulic presses.
CEBs are assembled onto walls using standard bricklaying and masonry techniques. The mortar may be a simple slurry made of the same soil/clay mix without aggregate, spread or brushed very thinly between the blocks for bonding.
- CEB technology has been developed for low-cost construction, as an alternative to adobe, and with advantages of load-bearing construction. A commercial industry and manufacturers of the mechanical presses, with cultural acceptance of the method. It’s use is widespread in the Southwestern states of USA such as New Mexico, Colorado, Arizona, California, and to a lesser extent in Texas. and in developing countries like Africa where they locally call it “Dutch Brick”. In Australia, there a few operators across the nation.