January 27th, 2008

Rammed Earth: Timeless Green Building

Posted by Jessica Jensen

Rammed earth may be one of the oldest building technologies on earth–and it happens to be an outstanding green building technique.  The technique originated in dry climates where wood was often not plentiful. The resulting structures are incredibly beautiful, durable and environmentally sustainable. We’ll explain what rammed earth building is, why it is green, and show you some great examples of residential rammed earth architecture.

How Are They Made? 

Rammed earth building, also known as pise de terre, involves using a damp mixture of dirt, clay sand, and gravel to create the structure of the building. Traditionally lime was often added to the mixture as a stabilizing element, but today cement is typically used. The builder creates a wooden form for the walls, and then adds the earth mixture into the frame.  Typically the walls are 5 to 12 inches thick. The moist mixture is compressed– or “rammed”– into the frame by a tamper. After a load of material is rammed, then more of the damp mix is added and it is compressed again. This process is repeated until the wall reaches the appropriate height. The frames are then removed and the walls are left to dry or “cure.” The walls need to dry in warm weather for several days– but full curing can take up to two years. After the curing process is complete, the structure is as strong as if it were built of rock.

What Makes Rammed Earth Green?  

Rammed Earth is considered a good green building technique for several reasons. First, the main ingredient–earth– is readily found close to the place where the building is to be constructed. Thus building the home does not require importing or transporting large amounts of building materials. Second, the use of earth for the structure means that very little wood is needed for the building, which is good as wood is a scarce resource. The forms used to build the structure are often made of wood, but these forms can be used again on another project. Third, rammed earth structures have great “thermal mass” which means that they keep indoor temperatures relatively stable; this reduces the need for excessive heating and/or cooling. Fourth, rammed earth structures are naturally fire-retardant. As an extra bonus, they are also bug-resistant.  All told, rammed earth homes are built from natural, local materials and have excellent energy-efficiency properties, making them solid examples of green building. (And the striations of the layers of earth make them uniquely attractive as well.)

What Do They Look Like? Who Builds Them?

There are several firms that specialize in rammed-earth design and building. Not surprisingly many of them are located in the Southwestern United States, where adobe building has been used for thousands of years.

Soledad Canyon Earth Builders is based in Las Cruces, New Mexico. They design custom rammed earth and adobe homes for their clients (they also do traditional frame/stucco designs). The homes they design have a distinctly Southwestern flair and they are gorgeous. They also factor in passive solar and natural breeze capture into their designs. Be sure to check out their photo gallery.

Rammed Earth Solar Homes, based in Oracle, Arizona, also has a stunning portfolio of residences. They build rammed earth homes, offices, and gardens. They lead builder, Quentin Branch, is available to consult with architects on projects as well. They also teach “Rammit Yourself” courses is you’re interested in building your own structure.  

If you happen to be in or near Canada, Terra Firma Builders builds spectacular rammed earth homes up North.  They employ a more modern aesthetic– and to beautiful effect. They are also winners of Western Living Magazine’s Residential Design Awards overall prize for Best Environmental Design in the small, medium and large home categories.