Adobe
From Wikipedia, the free encyclopedia
Adobe (
/əˈdoʊbi/,
UK /əˈdoʊb/;
[1] Arabic: الطوبة) is a
natural building material made from
sand,
clay,
water, and some kind of fibrous or
organic material (sticks,
straw, and/or
manure), which the builders shape into bricks using frames and dry in the sun. Adobe buildings are similar to
cob and
mudbrick buildings. Adobe structures are extremely durable, and account for some of the oldest existing buildings in the world. In hot
climates, compared with wooden buildings, adobe buildings offer significant advantages due to their greater
thermal mass, but they are known to be particularly susceptible to earthquake damage.
[2]
Buildings made of sun-dried earth are common in the
West Asia,
North Africa,
West Africa,
[3] South America, southwestern
North America,
Spain (usually in the
Mudéjar style), Eastern Europe
[4] and East Anglia, particularly Norfolk, known as 'clay lump.
[5] 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.
[6] (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.
[7] Its wide use can be attributed to its simplicity of design and make, and the economy of creating it.
[8]
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 (1-2 m) long.
[edit] Etymology
The word
adobe /əˈdoʊbiː/ has existed for around 4,000 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.
In more modern English usage, the term "adobe" has come to include a style of architecture popular in the
desert climates of
North America, especially in
New Mexico. (Compare with
stucco).
[edit] Composition
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.{{
[9] }}
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%) by weight.
[edit] Adobe bricks
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 characteristics, and partially due to the stability of a thicker brick versus a more standard-sized brick. Depending on the form into which the mixture is pressed, 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 straw, cement, or manure added to a standard adobe mixture can all produce a stronger, more crack-resistant brick.
[10] 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 it 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 (in South America).
[edit] Thermal properties
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 tropical 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.
[edit] Adobe wall construction
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 inches, 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 two stories because they are 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.
[edit] Adobe roof
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.
[edit] Roof materials
Depending on the materials available, a roof can be assembled using lengths of wood or metal to create a framework to begin layering adobe bricks. Depending on the thickness of the adobe bricks, the framework 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.
[edit] Traditional adobe roof
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.
[edit] Raising a traditional adobe roof
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 from which the beams and walls are made, choosing the attachments may prove difficult. A combination of 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 throughout 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]
[edit] Attributes
Depending on the materials, adobe roofs can be inherently fire-proof, which is a valuable attribute when the fireplace is kept lit during the cold nights. 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. The builders can make an adobe chimney by stacking simple adobe bricks in a similar fashion as the surrounding walls.
[edit] Adobe around the world
-
-
Mixing mud and straw in brick frames
-
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Adobe brick house under construction in
Kyrgyzstan
-
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Adobe brick house under construction in
Romania
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-
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Great Mosque of Djenné, famous building made from
banco, a type of adobe
[edit] See also
[edit] References
- ^ definition of adobe from Oxford Dictionaries Online. Retrieved 25 December 2010.
- ^ Collyns, Dan (2009-08-15). "Peru rebuilds two years on from quake". news.bbc.co.uk. Retrieved 2009-08-24. Cases where adobe structures were widely damaged during earthquakes include the 1976 Guatemala earthquake and the 2003 Bam earthquake.
- ^ Marchand, Trevor. The Masons of Djenne. Bloomington: University of Indiana Press, 2009
- ^ Museum of Lithuanian life Rumsiskes Lithuania (2011)
- ^ www.eartha.org.uk . Retrieved 19-2-2011.
- ^ 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 978-0-395-87274-1.
- ^ de Chazelles-Gazzal, Claire-Anne (1997). Les maisons en terre de la Gaule méridionale. Montagnac, France: Éditions Monique Mergoil. pp. 49–57.
- ^ Rose, William I.; Julian J. Bommer (2004). Natural hazards in El Salvador. Geological Society of America. p. 299. ISBN 978-0-8137-2375-4.
- ^ Vargas, J.; J. Bariola, M. Blondet (1986). "Seismic Strength of Adobe Masonry". Materials and Structures 9: 253–256. doi:10.1007/BF02472107.
- ^ Technical Information Online. "Mud Plasters and Renders - Technical Information Online - Practical Answers". Practicalaction.org. Retrieved 2010-11-09.
[edit] External links
- Building With Awareness A detailed how-to DVD video that shows adobe wall construction and their use as thermal mass walls
- Cal-Earth (The California Institute of Earth Art and Architecture) has developed a patented system called Superadobe, in which bags filled with stabilized earth are layered with strands of barbed wire to form a structure strong enough to withstand earthquakes, fire and flood.
- Earth Architecture - A website whose focus is contemporary issues in earth architecture.
- Earth Architecture and Conservation in East Anglia - British organisation that focuses on the proper maintenance and conservation of earth buildings in a region of the UK that has a long history of building with mud.
- Kerpic.org - A website on earthen architecture researches stabilized with gypsum.
- Kleiwerks - International organization recognized for their unique contribution to modern earthen and natural building techniques throughout the world, their focus is on education through hands on experience. Very experienced experts are contactable and there are regular demonstrations in the area.
- Valle de Sensaciones - Artistic construction with adobe, Experimental ground and theme park for creative living close to nature
- World Monuments Fund - Adobe Missions of New Mexico - Description of a project of the World Monuments Fund for the preservation of adobe churches in New Mexico, in the United States.
- Mud house - India's rural tradition
