The most ancient structures of the Southwest region of the United States still standing are represented in buildings made from adobe used in homes and Southwest missions. The early settlers of the region constructed homes of adobe because the materials were plentiful and at hand. Due to the lack of wood or masonry material, adobe was the choice of early shelters. Today, we have discovered that this material is not only abundant but also adaptable to changing climate and temperatures.
With the advance of the railroad, other materials used in the East made their way to the Southwest region and changed the face of local architecture. Most of the homes at the time were constructed of adobe due mainly to its high availability and low cost. It became more associated with the lower class which family members participated in the manufacturing of bricks using their feet and wooden molds. They relied entirely on the earth to provide the materials and not on any external shipments. Modern times have shown a trend towards adobe construction not only on aesthetics but also on practicality.
There are those who consider adobe the material of the poor, but now the thinking by the rich has renewed interest in this ancient building process. In some places, such as Santa Fe, New Mexico, these homes may cost beginning at $100,000. Certainly adobe homes can be constructed much cheaper. The manufacturing of adobe brick has become an industrial process. The camp of owners falls into two categories, those who hire contractors and those who do their own construction.
Traditionally, adobe brick measures 10x14x4 inches. Ideally, the mixture contains 20% clay and 80% sand. These materials are mixed with water and acquire a more fluid state that allows it to be poured into wooden forms with the above dimensions. When the water evaporates, the brick becomes hard, and it is then removed from the form. It is stacked one upon the other like fallen dominoes. About 30 days later, the bricks become as strong as cement.
The use of straw is commonly considered an essential part of the adobe brick, however, contemporary bricks of adobe do not contain it. The use of straw is thought to impart rigidity to the brick and prevent it from cracking during the curing process. If, however, the proper proportion of sand to clay is used this should not occur.
The basic mixture of clay and sand in adobe has been altered using emulsified asphalt. This is the component used in road construction. This imparts to the adode a waterproof quality. This incorporation is not fully accepted since the outer wall will be covered by stucco (plaster). If the wall is an inner patio or garden then its use is justified. “Purists” are not accepting to this idea and prefer the natural quality of adobe brick. Using asphalt will release gases that may prove harmful to man or the environment but no long-term studies of its effect have been done.