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Earthbag construction is an inexpensive building method using mostly local soil to create structures which are both strong and can be quickly built.


Earthbag development


Features

It is also
natural building A natural building involves a range of building systems and materials that place major emphasis on sustainability. Ways of achieving sustainability through natural building focus on durability and the use of minimally processed, plentiful or renew ...
technique developed from historic military
bunker A bunker is a defensive military fortification designed to protect people and valued materials from falling bombs, artillery, or other attacks. Bunkers are almost always underground, in contrast to blockhouses which are mostly above ground. T ...
construction techniques and temporary flood-control dike building methods. The technique requires very basic construction materials: sturdy sacks filled with organic material usually available on site. Standard earthbag fill material has internal stability. Either moist subsoil that contains enough
clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay pa ...
to become cohesive when tamped, or a water-resistant angular
gravel Gravel is a loose aggregation of rock fragments. Gravel occurs naturally throughout the world as a result of sedimentary and erosive geologic processes; it is also produced in large quantities commercially as crushed stone. Gravel is classifi ...
or crushed
volcanic rock Volcanic rock (often shortened to volcanics in scientific contexts) is a rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of volcanic origin. Like all rock types, the concept of volcanic ...
is used. Walls are gradually built up by laying the bags in courses—forming a staggered pattern similar to
bricklaying Brickwork is masonry produced by a bricklayer, using bricks and mortar. Typically, rows of bricks called ''courses'' are laid on top of one another to build up a structure such as a brick wall. Bricks may be differentiated from blocks by siz ...
. The walls can be curved or straight, domed with earth or topped with conventional
roof A roof ( : roofs or rooves) is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against rain, snow, sunlight, extremes of t ...
s. Curved walls provide good lateral stability, forming round rooms and/or domed ceilings like an
igloo An igloo (Inuit languages: , Inuktitut syllabics (plural: )), also known as a snow house or snow hut, is a type of shelter built of suitable snow. Although igloos are often associated with all Inuit, they were traditionally used only b ...
. Buildings with straight walls longer than in length need intersecting walls or bracing buttresses. International standards exist for bracing wall size and spacing for earthen construction in different types of seismic risk areas, most notably the performance-based standards of New Zealand recommended by the
ASTM International ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, ...
's earth building standards. Static shear testing shows that earthbag can reach similar strengths to New Zealand's reinforced adobe standards with specific soil strengths and reinforcement although unreinforced weak soil earthbag can have lower shear strength than unreinforced adobe. To improve friction between bags and wall tensile strength
barbed wire A close-up view of a barbed wire Roll of modern agricultural barbed wire Barbed wire, also known as barb wire, is a type of steel fencing wire constructed with sharp edges or points arranged at intervals along the strands. Its primary use is ...
is usually placed between courses.
Twine Twine is a strong thread, light string or cord composed of two or more thinner strands twisted, and then twisted together ( plied). The strands are plied in the opposite direction to that of their twist, which adds torsional strength to the co ...
is also sometimes wrapped around the bags to tie one course to the next, to hold in-progress structures together and keep courses well-seated on barbed wire prongs.
Rebar Rebar (short for reinforcing bar), known when massed as reinforcing steel or reinforcement steel, is a steel bar used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension. ...
can be hammered into walls to strengthen corners and opening edges and provide resistance against overturning. The structure is typically finished with
plaster Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "re ...
, either cement
stucco Stucco or render is a construction material made of aggregates, a binder, and water. Stucco is applied wet and hardens to a very dense solid. It is used as a decorative coating for walls and ceilings, exterior walls, and as a sculptural and a ...
on a strong mesh layer or an
adobe Adobe ( ; ) is a building material made from earth and organic materials. is Spanish for '' mudbrick''. In some English-speaking regions of Spanish heritage, such as the Southwestern United States, the term is used to refer to any kind of ...
or lime plaster, to shed water and prevent fabric UV damage. Finishes can differ from protected interior applications to exposed external applications. This construction technique is one of the most versatile natural building methods and can be used for benches, freestanding walls,
emergency shelter An emergency shelter is a place for people to live temporarily when they cannot live in their previous residence, similar to homeless shelters. The main difference is that an emergency shelter typically specializes in people fleeing a specific ...
s, temporary or permanent
housing Housing, or more generally, living spaces, refers to the construction and assigned usage of houses or buildings individually or collectively, for the purpose of shelter. Housing ensures that members of society have a place to live, whether ...
, or
barn A barn is an agricultural building usually on farms and used for various purposes. In North America, a barn refers to structures that house livestock, including cattle and horses, as well as equipment and fodder, and often grain.Alle ...
s and commercial buildings. Earthbag is frequently chosen for many small-to-medium-sized institutional structures in the developing world. Subgrade structures including underground and bermed dwellings (such as
Earthship An Earthship is a style of architecture developed in the late 20th century to early 21st century by architect Michael Reynolds. Earthships are designed to behave as passive solar earth shelters made of both natural and upcycled materials suc ...
s),
cistern A cistern (Middle English ', from Latin ', from ', "box", from Greek ', "basket") is a waterproof receptacle for holding liquids, usually water. Cisterns are often built to catch and store rainwater. Cisterns are distinguished from wells by ...
s,
spring box A spring box is a structure engineered to allow groundwater to be obtained from a natural spring. The spring box functions to protect the spring water from contamination, normally by surface runoff or contact with human and animals, and provides ...
es,
root cellar A root cellar (American English), fruit cellar (Mid-Western American English) or earth cellar (British English) is a structure, usually underground. or partially underground, used for storage of vegetables, fruits, nuts, or other foods. Its n ...
s, and retaining walls can be built with stabilized soil fill or with additional reinforcement and water-resistant gravel or sand fill.


Writers

Although Joseph Kennedy probably invented the term earthbag (as well as contained earth), Paulina Wojciechowska wrote the first book on the topic of earthbag building in 2001, ''Building with Earth: A Guide to Flexible-Form Earthbag Construction''. Kelly Hart developed a massive online database of earthbag information that encouraged idea sharing. Kaki Hunter and Doni Kiffmeyer worked on a variety of projects after studying with Khalili, calling earthbag "flexible form rammed earth". Their 2004 book, ''Earthbag Building: the Tools, Tricks and Techniques'', is available as an e-book. Free online booklets have been developed by different authors, including Owen Geiger and Patti Stouter. These include structural research and field testing techniques developed for rural areas. A 2011 e-book by Geiger, ''Earthbag Building Guide: Vertical Walls Step-by-Step'', provides photo illustrations of the process and discussions of new techniques for low-risk areas.


Proponents

Many like Akio Inoue, from Tenri University in Japan and Scott Howard of Earthen Hand have tested and built buildings. Hart, with Geiger, encouraged earthbag's development into different culturally and climatically-appropriate shapes. Robert Shear built an
earthship An Earthship is a style of architecture developed in the late 20th century to early 21st century by architect Michael Reynolds. Earthships are designed to behave as passive solar earth shelters made of both natural and upcycled materials suc ...
inspired earthbag house in Utah and Morgan Caraway of Sustainable Life School is building a house that incorporates earthship design principles as well. While Gernot Minke, the German professor of earthen architecture, first developed a technique of using bags filled with pumice to build walls, architect and builder
Nader Khalili Nader Khalili ( fa, نادر خلیلی; 1936–2008) was an Iranian-born American architect, author, and educator. He is best known for his inventive structures that incorporated a range of atypical building materials to provide shelter in the d ...
helped reintroduce earthbag construction as a modern technique called superadobe for humanitarian efforts (particularly for residential buildings) as well as natural flood control. Dr. John Anderton of South Africa has tested a triple channel bag version that reduces the slumping problems inherent in non-cohesive fill material like sand, and pioneered work in a narrow wall contained sand system which he calls E-khaya. Fernando Pacheco of Brazil pioneered the use of lighter HDPE mesh tubing for simpler hyperadobe walls. Rebuilding after natural disasters and in low-income regions around the world has included earthbag. Although heavy earthen walls are usually dangerous in quakes, Nepal's spring 2015 earthquakes left earthbag buildings in good condition near destroyed buildings. Engineer Nabil Taha developed the first general specifications for one type of exterior pinning reinforcement appropriate for the highest seismic risk zones. Several engineering students have tested uncured or low strength earthbag, and Build Simple has tested cured cohesive walls. Organizations building in Nepal are currently working with engineers to improve and refine reinforcement options for seismic-resistant earthbag.


Construction method

Construction usually begins by digging a
trench A trench is a type of excavation or in the ground that is generally deeper than it is wide (as opposed to a wider gully, or ditch), and narrow compared with its length (as opposed to a simple hole or pit). In geology, trenches result from ero ...
to undisturbed mineral
subsoil Subsoil is the layer of soil under the topsoil on the surface of the ground. Like topsoil, it is composed of a variable mixture of small particles such as sand, silt and clay, but with a much lower percentage of organic matter and humus, and ...
, which is partially filled with stones and/or gravel to create a
rubble trench foundation The rubble trench foundation, an ancient construction approach popularized by architect Frank Lloyd Wright, is a type of foundation that uses loose stone or rubble to minimize the use of concrete and improve drainage. It is considered more envir ...
. In high seismic risk regions a reinforced concrete footing or grade beam may be recommended. Earthbag buildings can also be built on conventional
concrete slab A concrete slab is a common structural element of modern buildings, consisting of a flat, horizontal surface made of cast concrete. Steel- reinforced slabs, typically between 100 and 500 mm thick, are most often used to construct floors and ...
s (though this is more expensive and uses more
embodied energy Embodied energy is the sum of all the energy required to produce any goods or services, considered as if that energy was incorporated or 'embodied' in the product itself. The concept can be useful in determining the effectiveness of energy-produ ...
than a rubble trench foundation) and can have a bermed or underground "floating" foundation like an earthship as well. Several courses of gravel in doubled woven bags form a water-resistant
foundation Foundation may refer to: * Foundation (nonprofit), a type of charitable organization ** Foundation (United States law), a type of charitable organization in the U.S. ** Private foundation, a charitable organization that, while serving a good cause ...
. Each layer usually has two strands of
barbed wire A close-up view of a barbed wire Roll of modern agricultural barbed wire Barbed wire, also known as barb wire, is a type of steel fencing wire constructed with sharp edges or points arranged at intervals along the strands. Its primary use is ...
on top, that attaches to the bag to prevent slippage and resists any tendency for the outward expansion of dome or rectangular walls. Bags on the course above are offset by —half of the wall width—similar to running bond in masonry. Bags can either be pre-filled with material and hoisted up, or bags or tubes are filled in place. The weight of the earthen fill locks the bag in place on the barbed wire below. A light tamping of the bags or tubes consolidates the moist clay-containing fill and creates interlocking bags or tubes anchored on the barbed wire.


Container types

Solid-weave
polypropylene Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene. Polypropylene belongs to the group of polyolefins a ...
is most popular, available around the world to transport rice or other grains. Polypropylene is low cost and resists water damage, rot, and
insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...
s. Tubes are often available from manufacturers who sew them into bags. Mesh tubes of soft crocheted poly fibers are also used, although stiff extruded mesh or woven mesh bags can also be used. Organic/natural materials such as
hemp Hemp, or industrial hemp, is a botanical class of '' Cannabis sativa'' cultivars grown specifically for industrial or medicinal use. It can be used to make a wide range of products. Along with bamboo, hemp is among the fastest growing plants ...
,
burlap Hessian (, ), burlap in the United States and Canada, or crocus in Jamaica and the wider Caribbean, is a woven fabric usually made from skin of the jute plant or sisal fibres, which may be combined with other vegetable fibres to make rope, nets, ...
(like "
gunny sack A burlap sack or gunny sack, also known as a gunny shoe, hessian sack or tow sack, is an inexpensive bag, traditionally made of fibres which are also known as "tow," such as hessian fabric (burlap) formed from jute, hemp or other natural fibres ...
s") can be used. Since these may rot, they should only be used with cohesive fills (containing a significant proportion of clay) that form solid masses when tamped.


Terminology

Earthbag is now a varied family of techniques. Each type of fill and container has different strength and reinforcement requirements. For hazardous locations, accurate terminology is needed. Contained earth (CE) is based on the original technique, but with specific soil strengths and reinforcement chosen for hazard levels. CE uses damp, cohesive, tamped bag fill, which bonds strongly with barbed wire and other reinforcement as the wall cures. CE is not "sandbags". Contained sand (CS) uses sand fill or any fill too dry or with poor cohesion that performs structurally like sandbags. CS must be built with solid-weave fabric bags and have good protection from fabric damage, relying on the strength of the bag fabric for wall strength. CS needs more vertical reinforcement for both shear and out-of-plane strength than CE, or may require a structural skin. Some builders use narrow bags of contained sand as wall infill. Contained gravel (CG) uses fill of any aggregate larger than coarse sand, usually in doubled rice bags, although strong mesh can be used. CG limits dampness transmission from footings. Modular CE is built in grain bags or similar tubes. Walls rely on attachment between barbed wire barbs and/ or added pins between courses. Solid CE is hyperadobe built in some type of knit raschel mesh tube, so that the damp earthen fill solidifies between courses.


Bag-fill materials

Generally inorganic material is used as filler, but some organic material (such as rice hulls) can be used if a strong matrix like wire mesh reinforces the plaster. Earthen fill may contain 5–50% clay, and can be "reject fines", "road base", "engineered fill", or local subsoil. "Raw" or un-stabilized soils cure as solid units but cannot withstand prolonged soaking. Subsoils with clay mold tightly and attach well to barbed wire prongs and rebar. Soil fill can contain a high proportion of aggregate, as long as it tamps and cures strongly. Crushed bottles, strong rubble, or plastic trash can be used, but high aggregate mixes may interfere with inserting rebar. Sands, stone dust and gravels can survive prolonged flood conditions, but most require special bracing during construction as well as some form of structural skin. Sand fill may be appropriate for several courses to provide a vibration damping building base, but becomes unstable in ordinary bags above in height. Cement, lime or bitumen stabilization can allow clay soil to withstand flooding or allow sands to be used in traditional bags with a non-structural plaster skin. Because earthbag walls are usually thick a large amount of stabilizer is needed. Thermal insulating properties are important for climates that experience temperature extremes. The thermal insulating value of a material is directly related to both the porosity of the material and the thickness of the wall. Crushed
volcanic rock Volcanic rock (often shortened to volcanics in scientific contexts) is a rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of volcanic origin. Like all rock types, the concept of volcanic ...
,
pumice Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of highly vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicular v ...
or
rice hulls Rice hulls (or rice husks) are the hard protecting coverings of grains of rice. In addition to protecting rice during the growing season, rice hulls can be put to use as building material, fertilizer, insulation material, or fuel. Rice hulls are p ...
yield higher insulation value than clay or sand. Untreated organic materials that could decay should not be used as part of a structural wall, although they can be used as infill. United Earth Builders has tried a light straw clay in the hyperadobe mesh tubing to form a layer 200 mm (8") thick outside of a dome. Thermal mass properties of earthen fill moderate temperature swings in climates that experience high temperature fluctuations from night to day. This
thermal flywheel effect In building design, thermal mass is a property of the mass of a building that enables it to store heat and provide inertia against temperature fluctuations. It is sometimes known as the thermal flywheel effect. The thermal mass of heavy structura ...
makes massive earth walls ideal for mild or hot and dry climates. Clay or sand also have excellent heat retention characteristics and, when properly insulated from the home's exterior, can serve as thermal mass in a
passive solar building design In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute solar energy, in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design because, unli ...
in cool climates, keeping interior temperatures stable year-round.


Reinforcement and structural performance

Solid CE may be built with less barbed wire in low-risk areas because walls solidify between courses. Earthbag using woven bags or tubes need barbed wire for any level of natural hazard since the bag-to-bag surfaces are slippery. Pins between courses do not contribute important linear out-of-plane strength. Walls of earthbag with barbed wire are more flexible than adobe and may resist collapse when carefully detailed. Earthbag of weak soil with no steel can be half the shear strength of unreinforced adobe, which is easily damaged in earthquakes. New Zealand's code detailing and plans allow unreinforced adobe walls to survive almost 0.6 g forces (comparable to Ss values for 2% probability of excedance in 50 years), but earthbag needs stronger soil to match this strength. Earthbag in Nepal surpassed this strength slightly by resisting forces above 0.7 g in early 2015. Domes tested in California resisted approximately 1 g forces, due to the stable shape of these less than diameter buildings. Current earthbag techniques of inserting rebar unattached to base and overlapping without connection may only resist 1.2 g or less, even if using very strong soil. Special reinforcement is needed Solid CE of strong soil has higher shear and out of plane strength than modular CE,. It may also allow the use of mesh for horizontal reinforcement in addition to or in place of barbed wire. Contained gravel or contained sand may perform best with wire wrapped around the sides of straight wall sections, alternating with the next course having barbed wire gift-wrapped under and over the same straight sections. Base walls of CG in high risk regions may need additional buttresses at the foundation level where builders cannot afford a reinforced concrete (RC) grade beam or footing. A narrower plastic mesh tube often used for erosion control wattle could be filled with gravel to allow a half-width RC ring beam under the wide walls.


Forming the house

A roof can be formed by gradually sloping the walls inward to construct a dome. Vaulted roofs can be built on forms. Or a bond beam is used under a traditional roof type. Hip roofs, gable-type trusses or vigas may be needed to reduce outward stress on earthen walls. Earth domes are inexpensive to build, but waterproofing them is complex or expensive in humid regions. Windows and doors can be formed with a traditional masonry
lintel A lintel or lintol is a type of beam (a horizontal structural element) that spans openings such as portals, doors, windows and fireplaces. It can be a decorative architectural element, or a combined ornamented structural item. In the case of ...
or with
corbel In architecture, a corbel is a structural piece of stone, wood or metal jutting from a wall to carry a superincumbent weight, a type of bracket. A corbel is a solid piece of material in the wall, whereas a console is a piece applied to the s ...
ing or brick-arch techniques, on temporary forms. Light may also be brought in by skylights, glass-capped pipes, or bottles placed between bag courses during construction.


Finishing

Cover the wall to prevent damage to the bags from UV rays or moisture with cement-based
stucco Stucco or render is a construction material made of aggregates, a binder, and water. Stucco is applied wet and hardens to a very dense solid. It is used as a decorative coating for walls and ceilings, exterior walls, and as a sculptural and a ...
, or lime or earthen
plaster Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "re ...
. If walls are 'raw' earth, an infill plaster of earth with straw is used to fill the nooks between bags or courses. A finish plaster is applied on top. Roof overhangs are helpful to reduce plaster
waterproofing Waterproofing is the process of making an object or structure waterproof or water-resistant so that it remains relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environme ...
requirements, although plaster on lower walls may be stronger and more water-resistant than plaster on upper walls. Some buildings use a planted-earth "living roof" ("green-roof") to top the structure, while others use a more conventional framing and roof placed atop earth-bag walls.


Environmental friendliness

Earthbag construction uses very little energy compared to other durable construction methods. Unlike concrete, brick or wood, no energy is needed to produce the earthen fill other than gathering soil. If on-site soil is used, little energy is needed for transportation. Unlike
rammed earth Rammed earth is a technique for constructing foundations, floors, and walls using compacted natural raw materials such as earth, chalk, lime, or gravel. It is an ancient method that has been revived recently as a sustainable building method. ...
construction, only human labor energy is required to tamp the soil lightly. The energy-intensive materials that used – plastic (for bags & twine), steel wire, and perhaps the outer shell of plaster or stucco – are used in relatively small quantities compared to other types of construction, often totaling less than 5% of the building materials. Buildings last a long time when maintained. However, if "raw" or unstabilized soil is used as fill, when the building is no longer useful the earthen fill can be
recycled Recycling is the process of converting waste materials into new materials and objects. The recovery of energy from waste materials is often included in this concept. The recyclability of a material depends on its ability to reacquire the p ...
into either garden areas, backfill, or new earthen buildings.


Use in disaster areas

Earthbag building techniques were also explored in Sri Lanka after the
2004 tsunami An earthquake and a tsunami, known as the Boxing Day Tsunami and, by the scientific community, the Sumatra–Andaman earthquake, occurred at 07:58:53 local time ( UTC+7) on 26 December 2004, with an epicentre off the west coast of northern Su ...
. Multiple earthbag construction projects have been completed in Haiti, most of these after the earthquake. First Steps HimalayaSTACEY K. Earthbag buildings a quake solution. Nelson Mail, The erial online August 29, 2015:3. Available from: Newspaper Source Plus, Ipswich, MA and other charities had built more than 50 earthbag buildings in Nepal prior to the April 2015 earthquake. Since then, local builders flocked to ongoing earthbag training opportunities, including those by Good Earth Global, which have led to official Nepal building code acceptance of this technique for residences. International NPOs have built hundreds of contained earth or earthbag buildings in Nepal as well, more residences than larger clinics or schools. NPOs are asking for more structural information to be better able to choose reinforcement types and intensity appropriate to local soil strength and seismic risk. University testing has begun but more is needed.


Colonization of the Moon

Khalili proposed using the techniques of earthbag construction for building structures on the Moon or other planets. Currently, it is quite expensive to lift a positive-mass payload from Earth. Thus, Khalili's techniques would seem to be an ideal solution as the requisite supplies would consist of lightweight bags and a few tools to fill them. He specified that such bags would probably have pre-sewn "
hook and loop Hook-and-loop fasteners, hook-and-pile fasteners or touch fasteners (often referred to by the genericized trademark velcro, due to the prominence of the Velcro Brand) consist of two components: typically, two lineal fabric strips (or, alterna ...
" (i.e.
Velcro Velcro, officially known as Velcro IP Holdings LLC and trading as Velcro Companies, is a British privately held company, founded by Swiss electrical engineer George de Mestral in the 1950s. It is the original manufacturer of hook-and-loop fast ...
) fastener strips in lieu of barbed wire.


See also

*
Earth structure An earth structure is a building or other structure made largely from soil. Since soil is a widely available material, it has been used in construction since prehistoric times. It may be combined with other materials, compressed and/or baked t ...
* Rice-hull bagwall construction *
Green roof A green roof or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a root barrier and draina ...
*
Natural building A natural building involves a range of building systems and materials that place major emphasis on sustainability. Ways of achieving sustainability through natural building focus on durability and the use of minimally processed, plentiful or renew ...
*
Super Adobe Superadobe is a form of earthbag construction that was developed by Iranian architect Nader Khalili. The technique uses layered long fabric tubes or bags filled with adobe to form a compression structure. The resulting beehive-shaped structur ...
*
Gabion A gabion (from Italian ''gabbione'' meaning "big cage"; from Italian ''gabbia'' and Latin ''cavea'' meaning "cage") is a cage, cylinder or box filled with rocks, concrete, or sometimes sand and soil for use in civil engineering, road buildin ...
*
Cellular confinement Cellular confinement systems (CCS)—also known as geocells—are widely used in construction for erosion control, soil stabilization on flat ground and steep slopes, channel protection, and structural reinforcement for load support and earth ...
(geocell)


References

{{Construction overview Construction Appropriate technology Soil-based building materials Sustainable building Articles containing video clips