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AdobeSurfaceCoatingRenewalOnWall

Renewal of the surface coating of an adobe wall in Chamisal, New Mexico

Adobe kilns from HABS

Detail of adobe kilns in Arizona

Adobe is a natural building material made from sand, clay, water, and some kind of fibrous or organic material (sticks, straw, and/or manure), which is shaped into bricks using frames and dried in the sun. It is similar to cob and mudbrick. Adobe structures are extremely durable and account for some of the oldest existing buildings in the world. In hot climates, compared to wooden buildings, adobe buildings offer significant advantages due to their greater thermal mass, but they are known to be particularly susceptible to earthquake damage.[1]

Buildings made of sun-dried earth are common in the West Asia, North Africa, West Africa[2], South America, southwestern North America, and in Spain (usually in the Mudéjar style). 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.[3] (Also, the Pueblo people built their adobe structures with handfuls or basketfuls of adobe, until the Spanish introduced them to the making of bricks.) Adobe brickmaking was used in Spain already in the Late Bronze Age and Iron Age, from the eighth century B.C. on.[4] Its wide use can be attributed to its simplicity of design and make, and the cheapness thereby in creating it.[5]

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 may be one to two yards (2 m) long.

EtymologyEdit

San Pedro de Atacama church

Church at San Pedro de Atacama, Chile.

The word adobe (pronounced /əˈdoʊbiː/) has come to us over some 4000 years with 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 evolved into Arabic al-tub (الطّوب 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.

Santa Fe adobe

Adobe style in Santa Fe, New Mexico

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

CompositionEdit

An adobe brick is a composite material made of clay mixed with water and an organic material such as straw or 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.[citation needed] The mixture is roughly half sand (50%), one-third clay (35%), and one-sixth straw (15%).[clarification needed]

Adobe bricksEdit

Milyanfan-adobe-bricks-8038

Adobe bricks near a construction site in Milyanfan, Kyrgyzstan

Bricks are made in an open frame, 25 cm (10 in) by 36 cm (14 in) being 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 in shade reduces cracking.

The same mixture to make bricks, without 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.[citation needed]

The brick’s thickness is preferred partially due to its thermal capabilities, and partially due to the stability of a thicker brick versus a more standard size brick. Depending on the form that the mixture is pressed into, adobe can encompass nearly any shape or size, provided drying time is even and the mixture includes reinforcement for larger bricks. Reinforcement can include manure, straw, cement, rebar or wooden posts. Experience has shown that straw, cement, or manure added to a standard adobe mixture can all produce a strong brick.[citation needed] A general testing is done on the soil content first. To do so, a sample of the soil is mixed into a clear container with some water, creating an almost completely saturated liquid. After the jar is sealed the container is shaken vigorously for at least one minute. It is then allowed to sit on a flat surface for a day or so until the soil has settled into layers or remains in suspension. Heavier particles settle out first so gravel will be on the bottom, sand above, silt above that and very fine clay and organic matter will stay in suspension for days. After the water has cleared percentages of the various particles can be determined. Fifty to 60 percent sand and 35 to 40 percent clay will yield strong bricks. The New Mexico US Extension Service recommends a mix of not more than 1/3 clay, not less than 1/2 sand, and never more than 1/3 silt. 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, with 100 million signed bricks, the ciudellas of Chan Chan and Tambo Colorado, both in Peru.

Thermal propertiesEdit

An adobe wall can serve as a significant heat reservoir due to the thermal properties inherent in the massive walls typical in adobe construction. In desert and other climates typified by hot days and cool nights, the high thermal mass of adobe levels out the heat transfer through the wall to the living space. The massive walls require a large and relatively long input of heat from the sun (radiation) and from the surrounding air (convection) before they warm through to the interior and begin to transfer heat to the living space. After the sun sets and the temperature drops, the warm wall will then continue to transfer heat to the interior for several hours due to the time lag effect. Thus a well-planned adobe wall of the appropriate thickness is very effective at controlling inside temperature through the wide daily fluctuations typical of desert climates, a factor which has contributed to its longevity as a building material. In addition, the exterior of an adobe wall can be covered with glass to increase heat collection. In a passive solar home, this is called a Trombe wall.

Adobe wall constructionEdit

Ancient Bam, 2002.png
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The citadel of Arg-é Bam: The world's largest adobe structure, dating to at least 500 BC.

When building an adobe structure, the ground should be compressed because the weight of adobe bricks is significantly greater than a frame house and may cause cracking in the wall. The footing is dug and compressed once again. Footing depth depends on the region and its ground frost level. The footing and stem wall are commonly 24" and 14", much larger than a frame house because of the weight of the walls. Adobe bricks are laid by course. Each course is laid the whole length of the wall, overlapping at the corners on a layer of adobe mortar. Adobe walls usually never rise above 2 stories because they're load bearing and have low structural strength. When placing window and door openings, a lintel is placed on top of the opening to support the bricks above. Within the last courses of brick, bond beams are laid across the top of the bricks to provide a horizontal bearing plate for the roof to distribute the weight more evenly along the wall. To protect the interior and exterior adobe wall, finishes can be applied, such as mud plaster, whitewash or stucco. These finishes protect the adobe wall from water damage, but need to be reapplied periodically, or the walls can be finished with other nontraditional plasters providing longer protection.

Adobe roofEdit

The traditional adobe roof has been generally constructed using a mixture of soil/clay, water, sand, and other available organic materials. The mixture was then formed and pressed into wood forms producing rows of dried, earth bricks that would then be laid across a support structure of wood and plastered into place with more adobe. For a deeper understanding of adobe, one might examine a cob building. Cob, a close cousin to adobe, contains proportioned amounts of soil, clay, water, manure, and straw. This is blended, but not formed like adobe. Cob is spread and piled around a frame and allowed to air dry for several months before habitation. Adobe, then, can be described as dried bricks of cob, stacked and mortared together with more adobe mixture to create a thick wall and/or roof.

Roof materialsEdit

Depending on the materials available, a roof can be assembled using lengths of wood or metal to create a frame work to begin layering adobe bricks. Depending on the thickness of the adobe bricks, the frame work has been performed using a steel framing and a layering of a metal fencing or wiring over the framework to allow an even load as masses of adobe are spread across the metal fencing like cob and allowed to air dry accordingly. This method was demonstrated with an adobe blend heavily impregnated with cement to allow even drying and prevent major cracking.

Traditional adobe roofEdit

More traditional adobe roofs were often flatter than the familiar steeped roof as the native climate yielded more sun and heat than mass amounts of snow or rain that would find use in precipitous roofs. Cement may be introduced to prevent moisture from penetrating the composite of mud and organic matter. Vigas are beams across the roof that support the roof.

Raising a traditional adobe roofEdit

To raise a flattened adobe roof, beams of wood or metal should be assembled and span the extent of the building. The ends of the beams should then be fixed to the tops of the walls using the builder’s preferred choice of attachments. Taking into account the material the beams and walls are made from, choosing the attachments may prove difficult. In combination to the bricks and adobe mortar that are laid across the beams creates an even load-bearing pressure that can last for many years depending on attrition.

Once the beams are laid across the building, it is then time to begin the placing of adobe bricks to create the roof. An adobe roof is often laid with bricks slightly larger in width to ensure a larger expanse is covered when placing the bricks onto the beams. This wider shape also provides the future homeowner with thermal protection enough to stabilize an even temperature through out the year. Following each individual brick should be a layer of adobe mortar, recommended to be at least an inch thick to make certain there is ample strength between the brick’s edges and also to provide a relative moisture barrier during the seasons where the arid climate does produce rain.[citation needed]

AttributesEdit

Adobe roofs can be inherently fire-proof, an attribute well received when the fireplace is kept lit during the cold nights, depending on the materials used. This feature leads the homeowner and builders to begin thinking about the installation of a chimney, a feat regarded as a necessity in any adobe building. The construction of the chimney can also greatly influence the construction of the roof supports, creating an extra need for care in choosing the right materials. An adobe chimney can be made from simple adobe bricks and stacked in similar fashion as the surrounding walls. Basically outline the location and perimeter of the hearth, minding the safety elements common to a fireplace, and begin to stack and mortar the walls with pre-made adobe bricks, cut to size.

Around the worldEdit

See alsoEdit

NotesEdit

  1. Collyns, Dan (15-08-2009). "Peru rebuilds two years on from quake". news.bbc.co.uk. http://news.bbc.co.uk/2/hi/americas/8201971.stm. Retrieved 2009-08-24.  Cases where adobe structures were widely damaged during earthquakes include the 1976 Guatemala earthquake and the 2003 Bam earthquake.
  2. Marchand, Trevor. The Masons of Djenne. Bloomington: University of Indiana Press, 2009
  3. Beck, Roger B.; Linda Black, Larry S. Krieger, Phillip C. Naylor, Dahia Ibo Shabaka, (1999). World History: Patterns of Interaction. Evanston, IL: McDougal Littell. ISBN 0-395-87274-X. 
  4. de Chazelles-Gazzal, Claire-Anne (1997). Les maisons en terre de la Gaule méridionale. Montagnac, France: Éditions Monique Mergoil. pp. 49–57. 
  5. Rose, William I.; Julian J. Bommer (2004). Natural hazards in El Salvador. Geological Society of America. p. 299. ISBN 0813723752. 

External linksEdit

This page uses Creative Commons CC-BY-SA licensed content from Adobe on Wikipedia (view authors).

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