¯  Adobe

      Adobes are earthen bricks made from a saturated mixture of clay, sand and straw, hand-poured or pressed into forms, then dried in the sun.  The dried adobes are stacked with a mud or concrete mortar to create thick-walled structures.  Adobe has been used for centuries in traditional earth-building areas such as South America and the southwestern United States.  Soundproof, well-insulated, natural, and with a unique architectural presence, adobe structures have lasted for thousands of years, with far less maintenance required than for conventional homes.

     Adobe construction, in combination with good passive solar design, creates a year-round, energy-saving solution.  The thick walls create "thermal mass," which helps regulate interior temperatures by absorbing excess heat during the day and slowly releasing it at night.  The use of high-mass walls, insulation, and a large southern exposure can cut energy use in the winter and cooling costs in the summer. 

 

¯  Cob

      Cob is an ancient technique of building monolithic (meaning "all one piece") walls using "cobs" of moist earth and straw.  Cob has similar thermal properties to adobe and rammed earth.  It is a multifaceted building material, applicable to many  conditions because of its ease of use, sculptural qualities, strength, and thermal mass, and it is also useful in combination with other techniques. 

     Cob building entails mixing local subsoil with sand and/or clay and straw or other natural materials to create a stiff mud, which is formed into small loaves (cobs).  At the wall, the builder presses and flattens the cobs together onto the growing structure to form a monolithic wall on top of a stone or concrete foundation.  Cob can also be forked as a mass onto the wall then shaped into the next layer. 

     The walls (possibly up to six feet thick) proceed in layers or "lifts" from 6" to 18" high, and work continues after letting each layer solidify.  Windows and other details are "cobbed" into place, and niches and reliefs are easy to create.

 

¯ Compressed Earth Blocks

      Compressed earth blocks are similar to adobes, with the main difference being that they are not fully saturated with water during formation.  The blocks are created using a variety of machines.  They tend to be more dense and uniform than adobes.  Because of their uniformity, compressed earth blocks need little mortar, and can be dry-stacked as well.  This uniformity generally speeds up the laying process.

 

¯ Earthen Floors

       Tamped or poured-earth floors can provide an excellent source of thermal mass in passive solar designs.  The technique involves pouring or tamping one or several layers of an earth mixture over a substrate of gravel, pumice or sand (with a sublayer of straw-clay in some cases).  Hardening agents such as ox blood, lime, cement or glue may be added. 

     The mixture is allowed to dry, and any cracks are filled with more mud mixture.  Cracking can be allowed to occur at random, resulting in a flagstone-like pattern, or it can be controlled by etching the floor to create a tile-like effect.  Once the floor is completely dry, it is sealed, most commonly with successive applications of linseed oil and turpentine. The floor is most often coated with wax to protect the surface.

 

¯ Natural Plasters and Finishes 

      Historically, most earthen and masonry structures have been protected by mud- or lime-based plasters.  While still common in other parts of the world, lime and mud plasters are relatively rare in the U.S.  These plasters are breathable, soft to the touch, beautiful, economical, and easy to work with and repair.  Less brittle than cement-based plasters, those based on lime or mud adhere and "move" with the underlying wall, lessening cracks and allowing the wall to “breathe.” 

 

¯ Rammed Earth

      Rammed earth is an ancient earth-building technique with the advantages of excellent thermal mass, strength, comfort, and beauty.  It is labor-intensive, but updated building techniques have made rammed earth more competitive with conventional construction costs.  Built in a variety of climates, rammed earth has been used to build structures of up to seven stories.

     Rammed earth consists of walls made from moist, sandy soil, or stabilized soil, which is tamped into forms atop an appropriate foundation (usually stone or concrete).  Walls are a minimum of 12" thick, and the materials cure in the wall.  Different soil types can be layered to create decorative effects. As with other earthen materials, the wall is topped by a concrete bond beam that supports the roof.

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