adobe

Adobe is a natural building material composed of sand, sandy clay and straw or other organic materials, which is shaped into bricks using wooden frames and dried in the sun. It is similar to cob and mudbrick. Adobe structures are extremely durable and account for the oldest extant buildings on the planet. Adobe buildings also offer significant advantages in hot, dry climates; they remain cooler as adobe stores and releases heat very slowly.

Buildings made of sun-dried earth are common in the Middle East, North Africa, and in Spain (usually in the Mudéjar style), but adobe had been in use by indigenous peoples of the Americas in the Southwestern United States, Mesoamerica, and the Andean region of South America for several thousand years, although often substantial amounts of stone are used in the walls of Pueblo buildings. This method of brickmaking was imported to Spain in the 16th century by Spaniards who had traveled to Mexico and Peru.

A distinction is sometimes made between the smaller adobes, which are about the size of ordinary baked bricks, and the larger adobines, some of which are as much as from one to two yards long.

The word Adobe ([əˈdəʊbiː] or [əˈdoʊbi]) has come down to us over some 4000 years with astonishingly little change in either pronunciation or meaning: the word can be traced from the Middle Egyptian (c. 2000 BC) word dj-b-t "mud [i.e., sun-dried] brick." As Middle Egyptian evolved into Late Egyptian, Demotic, and finally Coptic (c. 600 BC), dj-b-t became tobe "[mud] brick." This in turn evolved into Arabic at-tub (al "the" + tub "brick") "[mud] brick," which was assimilated into Old Spanish as adobe [aˈdobe], still with the meaning "mud brick." English borrowed the word from Spanish in the early 18th century.

In more modern usage, the term "adobe" has come to mean a style of architecture that is popular in the desert climates of North America, especially in New Mexico. (Compare with stucco).

Composition of adobe

An adobe brick is made of clay mixed with water and an organic material such as straw or animal dung. The soil composition typically contains clay and sand. Straw is useful in binding the brick together and allowing the brick to dry evenly^{citation needed]}. Dung offers the same advantage and is also added to repel insects.

Adobe bricks

Bricks are made in an open frame; 25 cm (10 inches) by 36 cm (14 inches) is a reasonable size, but any convenient size is acceptable. The mixture is molded by the frame, and then the frame is removed quickly. After drying a few hours, the bricks are turned on edge to finish drying. Slow drying (shaded) avoids cracking.

The same mixture to make bricks, less the straw, is used for mortar and often for plaster on interior and exterior walls. Some ancient cultures used lime-based cement for the plaster to protect against rain damage.

The largest structure ever made from adobe (bricks) was the Bam Citadel, which suffered serious damage (up to 80%) by an earthquake on December 26, 2003. Other large adobe structures are the Huaca del Sol in Peru, built using 100 million signed bricks, the ciudellas of Chan Chan and Tambo Colorado, both also in Peru.

Thermal properties

An adobe wall can serve as a significant heat reservoir. A south-facing (in the Northern Hemisphere) adobe wall may be left uninsulated to moderate heating and cooling. Ideally, it should be thick enough to remain cool on the inside during the heat of the day but thin enough to transfer heat through the wall during the evening. The exterior of such a wall can be covered with glass to increase heat collection. In a passive solar home, such a wall is called a Trombe wall. Adobe has a relatively dense thermal mass; therefore this type of construction is most useful in tropical climates. In temperate climates it is less effective to heat a structure this way due to heat leaching by the ground and walls.

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