Adobe Adobes are sun-dried mud bricks stacked with a mud mortar to create thick-walled structures. Their use dates back centuries in traditional earthbuilding areas such as North Africa, the Middle East, South America and the southwestern United States, where in all cases this building method is still in widespread use. Dramatic examples of vaulted and domed structures built entirely of earth still stand after centuries in the Middle East, testament to adobe's timeless beauty and structural integrity. While in the "South" its use is mostly confined to those too poor to have access to other building materials, in the southwest U.S., adobe is often used by the very rich, illustrating its wide appeal. Adobe is appropriate in areas which are labor-rich and capital-poor, because it is so labor intensive, using local materials and simple tools. Adobe bricks are made with a completely saturated mixture of clay and sand (and sometimes straw or manure), poured or pressed into forms, which are then removed. After the bricks have dried for several days, they are turned on edge for further drying, then stacked for transport or for use on site. The adobes are laid on an appropriate foundation (usually stone or concrete) using typical masonry techniques with thick joints to take up the difference in size of the adobes. Typically, mud mortar is used, but a concrete- or lime-based mortar has also been employed in certain cases. Various stabilizers for the adobes themselves have been developed, with most, however, relying on cementitious or asphalt-based compounds. While adobe is widely appropriate, certain precautions must be taken to ensure the durability of construction. Wide eaves are often appropriate to protect the walls from rain, and foundations must protect the walls from splashing. Mud plaster is traditionally used to finish adobe structures with minimal or no overhang of the roof, requiring replenishment every few years. Cement stucco has also been used in an effort to provide longer lasting coatings, but in many cases has proven to be destructive, as the brittle stucco can crack, letting in water which dissolves the underlying adobes. Because the stucco can hide this damage, buildings can collapse before anything is sensed to be wrong. In addition, indoor moisture cannot escape, building up on the inside of cement stucco, eroding the wall. Because of this, there has been a return to favor of traditional plasters using mud, straw and other natural materials (see Natural Plasters and Finishes.) Many building codes place severe restrictions on adobe construction, essentially limiting it (and other earth-based building technologies) to the desert southwest. Bamboo Bamboo is a species of plant in the grass family. It grows very quickly, providing renewable material for building, tools, and utensils as well as edible shoots. Common in the tropics, many species of bamboo grow in temperate climates as well. Strong and beautiful, bamboo has seen a recent resurgence in popularity with builders. Bamboo as a building material is not commonly known in North America because of limitations on the import of living plants, and lack of knowledge of traditional techniques. This ignorance is beginning to change, however, as timber prices rapidly escalate, and western builders become aware of innovative uses of bamboo that have originated in Asia, Central America and South America. Utilized for millenia in these countries, bamboo can replace wood and steel in many applications. It can replace rebar in concrete, as pins in straw bale construction, to create trusses and other structural members, as decorative elements, and has even been used as plumbing. Its widespread use in tropical areas, as well as unsustainable harvest for export, can have its dangers: indiscriminate cropping can decimate stands and endanger interdependent ecosystems. To address this danger, an effort to create sustainable growing programs similar to those for tropical hardwoods is currently in development. Cob Cob is an ancient technique of building monolithic walls using "cobs" of moist earth and straw. It is being rediscovered as a multifaceted building material applicable to a number of conditions. Virtually forgotten in North America, cob was popularly reintroduced by Welsh architect and builder Ianto Evans, who inspired intense public interest in his self-built cob home created for under $500. A sculptural technique which lends itself to curved organic shapes, cob requires minimal tools and can be built by young and old alike. The process of building with cob entails mixing local earth with sand and/or clay (depending on the composition of the base earth) and straw or other fibrous materials to create a stiff mud which is formed into small loaves (cobs). These cobs are then mashed together to form a monolithic wall on top of a stone or concrete foundation. The relatively thick walls (they have been known to be up to six feet thick) proceed in layers or "perches" averaging 18" high before slumping occurs. After a period of time to let each layer solidify, work can continue. Irregularities can be shaved off with a spade or other sharp tool as work progresses. A particular favorite of natural builders for its ease, sculptural qualities, strength, and thermal mass, cob is also useful in combination with other techniques. Windows and other details are "cobbed" into place, and niches and reliefs are easy to create. While extremely economical for owner-builders, cob is very labor intensive and time consuming, with walls taking up to a year to fully cure. In addition, the curving architecture is not to all tastes. Cob has been used mostly in informal or experimental buildings in the U.S. while code testing procedures are investigated. Cob construction is undergoing a revival in England as well, where proponents are rediscovering five hundred year old houses in perfect condition. Compressed Earth Blocks Compressed earth blocks are similar to adobes, with the main differences being they are not fully saturated with water, are more dense than adobes, and are usually significantly more uniform. These blocks are created using a variety of machines. Some, like the Cinva-Ram invented in South America, use human labor and are relatively inexpensive. Expensive fuelpowered machines, on the other hand, can produce thousands of bricks in a day. Because of their uniformity, compressed earth blocks need little mortar, and can even be dry-stacked. This uniformity also speeds up the laying process and results in straighter walls. A house was built several years ago by CRATerre, a French earthbuilding education and research group, in a total of 24 hours using compressed earth blocks. More recently, an inexpensive, innovative machine has been invented in Auroville, India, which can make a wide variety of sophisticated block shapes using human power. This machine was demonstrated at the UN Habitat II conference in Istanbul in 1996, where a domed prototype house was built in a week by volunteers and local labor. Earthbags Earthbags are soil-filled fabric sacks or tubes used to create walls and domes. Traditionally used for flood control and by armies to create bunkers, this method of construction has been recently turned to a variety of natural construction purposes. The technique has been used by Gernot Minke of Germany, and is currently being pioneered in the U.S. by Persian architect Nader Khalili of the California Institute of Earth Art and Architecture (Cal Earth). The use of earthbags is still in its infancy, but holds much promise as a quick, easy and forgiving technique which uses minimally processed soil and few tools. To build with this technique, moistened soil is placed into a bag set in place on the wall, the bag is lowered into place, then compressed using a hand tamper. Heavy earth mixtures can be used with weaker burlap bags as the compressed soil makes the bags redundant once it sets. Stronger, structural polypropylene bags are preferable for sandy soils. Recycled sacks are often available free or at minimal cost. In earthquake prone areas, a layer of long-point barbed wire is used as "mortar" between the bags to contain slipping. Domes using these materials are easily achieved with a corbelling system utilizing long tubes made of the polypropylene bag material. Numerous natural builders have taken to using the bags as simple foundations for straw bale or cob structures, or for simple site walls. Recent projects in Mexico and Nova Scotia have used gravel-filled bags as foundations for straw-bale walls to minimize rising damp. Disadvantages with earthbag construction are that resulting structures may seem excessively "organic" to some and also require quite of lot of plaster in order to create smooth walls. Advantages of this technique include the opportunity to build in wet conditions and in sites prone to flooding. Cheap and easily transported, the bags could also be used for disaster relief housing. Successful ICBO-approved testing has been undertaken by Cal-Earth, and a code-approved public project was undertaken in Hesperia, California. Earthen Floors The use of tamped or poured earth mixtures to create floors is currently undergoing a renaissance in the southwest U.S. Methods range from the African use of fresh cow dung sealed with ox blood, to sealed earth mixtures.The technique involves pouring or tamping one or several layers of an earth mixture over a substrate of gravel, pumice or sand (a sublayer of strawclay has also been used by builder Robert Laporte for insulation). Hardening agents such as blood, lime, cement or glue may be added. This mixture is allowed to dry and any cracks are filled with more mud mixture. Cracking can be allowed to occur at random, resulting in a flagstone-like pattern, or can be controlled by incising the floor to create a tile-like effect. When the floor is entirely dry, it is sealed, most commonly with successive applications of linseed oil and turpentine. The floor is often coated with wax to protect the surface. Minor disadvantages of this system are its relative damageability and need for maintenance. It can also be time consuming to install because of long drying times. Advantages include its aesthetic values, softness to the feet, and reliance on cheap, often free local materials. Earthships "Earthships" are the name for the independent living structures utilizing passive solar design and recycled materials developed by Michael Reynolds of Solar Survival Architecture. While not exclusively reliant on "natural" materials, earthships replace some conventional materials with recycled trash which is found scattered all over the planet. Earthships are a system rather than a technique: typically, earthships are dug into south facing hillsides; soil-filled tires are then stacked like giant bricks to form side and interior walls providing a source of thermal mass. Old bottles and cans are used to create a variety of detail features and to fill in gaps between tires. The building is framed in wood on the south side and roofed with metal to collect rain water. Other systems include integrated wastewater treatment, photovoltaic electrical systems, solar hot water and passive solar heating. Advantages of the system include self-sufficiency in all aspects, the use of recycled materials and local soil, and technical and aesthetic sophistication. Disadvantages include the complexity of building such a structure and the amount of labor required which makes it out of reach for many owner-builders. The earthship concept has become a well-known and popular building system, especially in northern New Mexico. Several earthship communities have been built, and the system has received widespread media attention. Other builders have used the stacked tire concept to build houses which don't contain all of the systems of Reynold's designs. Hybrid Structures Hybrid building techniques are a fascinating outgrowth of the efforts of a few visionary natural builders and the sharing of ideas in the natural building colloquia. The basic concept is that several techniques can be combined for increased building efficiency or unique artistic effect. An example is to combine a thermal mass technique such as cob or rammed earth on the south side of a house, with an insulative system such as straw bales or straw-clay on the north side, taking advantage of the best qualities of each system. New solutions to common problems have begun to evolve from such creative combinations. A disadvantage of this approach is the lack of practitioners with wide experience in a number of techniques, pointing to the need for increased communication and sharing of ideas, and the elimination of dogmatic insistence on the preference of one system over another. Light Straw-Clay (Leichtlehm) Leichtlehm (literally "light-loam") is a German technique of ramming loose straw coated with a clay slip into forms as an infill for timber frame structures. This technique has been popularly reintroduced to North America by Robert Laporte who teaches natural building courses nationwide. He has been joined recently by Frank Andresen, a builder with extensive natural building experience in his native Germany. The technique consists of surrounding a frame structure with a thick infill of the straw-clay mixture. The frame is usually fully expressed on the interior of the building to take advantage of the beauty of the timber frame joinery. A lighter frame of wood is built on the eventual outside face of the building as an anchoring system for the straw-clay walls. Loose straw and a clay slurry are tossed with pitchforks or mixed mechanically, then allowed to age for up to several days in order to allow the straw to absorb the extra moisture and thus create a stickier and more easily tamped mixture. For higher insulation values less clay can be used. Slip forms are set up between the framing members, and the straw clay mixture is tamped by hand in two-foot layers. Occasional horizontal members spanning between the exterior frame are placed in order to "lock in" the straw-clay mass. Frank Andresen places the ends of these horizontal members at the upper ends of vertical slots in the frame in order to allow for shrinkage of the straw-clay as it dries. Once each layer is complete, the slip form is moved up and the next layer is tamped until the wall is complete. The walls are allowed to dry before final plastering occurs. Any shrinkage is taken up by stuffing more of the mixture into the cracks. Robert Laporte commonly uses straw-clay stuffed loose between rafters as insulation, with the clay discouraging pests. He has also used it as an insulating layer underneath earthen floors. Frank Anderson has demonstrated a system of strawclay tiles which can be placed between roof rafters as insulation and as a plastering surface. He's also introduced straw-clay bricks that can be used like lightweight adobes. A variant on the straw-clay technique utilizes wood chips mixed with clay; the resulting mixture is poured into removable or sacrificial forms. This technique can also be used to create lightweight bricks. Highly accurate buildings are possible with the timber frame and straw-clay technique, allowing a "natural" structure which compares in looks to conventional stick-frame housing, making it an appealing option for some homeowners. Some disadvantages of the technique include its highly labor intensive nature, and the long drying time. The straight walls achievable with this method, however, are desired by builders in southern countries who seek a western look in their houses, and to whom an "organic" structure is "old-fashioned." Hemp and other Fibers Hemp and other fiber-producing plants as kenaf and sawgrass are currently being investigated as potential building products. Commonly used for numerous purposes before drug laws made its cultivation illegal, non-psychoactive hemp is being rediscovered as a source of fiber, oil, and hurd; these can replace less ecologically sound wood or petrochemical products in a variety of building applications. Examples include pressed-hemp fiberboards, and use of the inner pith or "hurd" as an additive for a lime-based concretelike material. Similar studies and experiments are being done with Kenaf and other fibers. Use of hemp and other fibers have several advantages. Because hemp provides four times the usable fiber per acre as wood, grows in degraded soils, and needs little chemical processing, this annually renewable crop is being considered more and more seriously. Several European countries, including England, Hungary and the Ukraine, have joined major hemp producers such as China to grow this neglected and useful plant for a variety of uses. Drawbacks include the reliance on expensive imported fiber because of misguided laws which restrict the growing of nonpsychoactive strains of the plant in the U.S. Domestic manufacturers are also hampered by the lack of modern processing machinery. Living Roofs The Archibio architecture group in Quebec has updated the ancient sod roof of Europe with a concept called the "living roof." This type of roof has several advantages: it is an aesthetic feature, helps the house blend into its environment and provides climatic stabilization. Particularly useful in wet snowy areas, this style of earthen roof has more limited applicability in dry climates. A living roof is built on top of a sufficiently strong frame with carefully applied waterproofing, as it is very difficult to locate leaks once the growing medium is in place. The living roof itself is a compost based system, usually a base of straw left to decompose within which native or introduced plants can then take root. The living roof will need ongoing tending, and could be a fire hazard in hot dry climates. It is advantageous in that it protects the waterproofing from damage by ultraviolet radiation, and precludes the need for tiles or other shingles. Natural Plasters and Finishes Before the advent of portland cement, most earthen and masonry structures were protected by mud- or lime-based plasters. While still common in other parts of the world, lime and mud plasters are relatively rare in the U.S. The advantages of these plasters include "breathability," softness to the touch, aesthetic qualities, workability and easy reparability, as well as economy of materials. Less brittle than cement-based plasters, those based on lime or mud adhere and "move" with the underlying wall, lessening cracks and often making stucco netting unnecessary. Because they can erode unacceptably when exposed to rain, exterior mud plasters are generally used in drier climates. Protected from rainfall and other liquid moisture, earthen plasters are viable in any climate. They have fallen into disuse in the U.S. because of their disadvantages of slow setting times, the perceived need to renew them every several years due to weathering, and discrimination against their use by building codes. However, as the limitations of cement-based plasters become increasingly evident (see Adobe section), many natural builders are returning to ancient plastering techniques from around the world. An extensive collection of traditional plaster and paint recipes and application methods can be found in The Straw Bale House and The Earthbuilders' Encyclopedia (see Bibliography). Paper Blocks Printer Eric Patterson of New Mexico has discovered a use for his (and anyone's) waste paper. He pulps this paper and mixing it with cement, makes lightweight, strong and easily-worked paper blocks. This material can also be poured and used as mortar or plaster. Only a few examples of this system with varying degrees of success currently exist. While most recipes call for as much cement as is used in a solid concrete wall, some practitioners are experimenting with clay as a binder. Concerns include flammability with some examples having burned, and the effects of freeze-thaw. Rammed Earth Rammed earth is an ancient earthbuilding technique currently undergoing a renaissance in the U.S. and abroad. It has been revived in France by CRATerre, in Australia by Giles Hohnen and others, while its main proponent is the U.S. is David Easton, author of The Rammed Earth House (see Bibliography). These pioneers have updated the technique with improved engineering, sophisticated forms, and innovative design to make rammed earth competitive with conventional construction, even in earthquake-prone California. While rammed earth is in limited use in the U.S., builders in western Australia have captured up to 20% of the housing market in many areas. Rammed earth has the advantages of excellent thermal mass (which in many climates may be a disadvantage unless insulated), strength, comfort and beauty. Rammed earth can be built with simple forms and tools with less handling than other earthbuilding techniques, as the material cures in the wall. It can be built in a variety of climates. Walls do not need to be plastered and will last for hundreds, even thousands of years (the great wall of China is partially built of rammed earth). It has been used to build structures of up to thirteen stories in Yemen. First proceeding by setting up forms on top of an appropriate foundation (usually stone or concrete), a soil mixture with a clay content of 20% and a moisture content of 10% is then rammed in layers or "lifts" of 6-8 inches using mechanical or hand tampers. Different soil types can be used to create decorative effects and the whole is topped by a concrete bond beam which then holds the roof. Procedures are discussed in detail in The Rammed Earth House. To build efficiently for the North American market, David Easton has developed sophisticated forms and tools which decrease time and labor costs. It is, however, still extremely labor intensive, and codes demand intensive reinforcing in earthquake-prone areas. In an effort to make rammed earth even more competitive, Easton has developed a system called Pneumatically Impacted Stabilized Earth (PISE). In this system moist earth is sprayed against a single form allowing thick walls to be built extremely quickly. Recycled Building Materials In an effort to reduce waste, many builders are seeking to reuse materials which would otherwise end up as trash. Many structures, especially in urban areas, can be effectively rehabilitated, saving immense amounts of new construction costs, maintaining important cultural links, as well as avoiding massive amounts of landfill waste. Other structures can be carefully dismantled, saving lumber, bricks and other recyclables for new projects. High quality old-growth timber has been salvaged from old barns which is then used for new homes. Waste wood can be reused to create a number of board products. Many of these, unfortunately, depend on toxic binders, but efforts to make healthy alternatives continue. Additionally, sawdust and recycled plastic have been used to create long-lasting lumber substitutes. Efforts in these areas have been spearheaded by the Wood Reduction Clearinghouse. Windows, doors and other fixtures can be refurbished and reused, saving valuable architectural heritage and creating unique resources for owner-builders. Others use "junk" in innovative ways (see Earthships.) The advantage of this approach is the obvious environmental benefits and aesthetic possibilities. Disadvantages include the time, labor and cost to build with old treasures because of refurbishment, special detailing necessary, and the time spent to find, dismantle and transport these resources. Straw Bale Construction The use of baled straw to create superinsulated walls has become an extremely popular method of construction in recent years. Most common in North America, bale buildings have been built around the world. Originally used by the pioneers of the Nebraska sandhills, straw bales are cheap to buy and easy to build with, lending themselves to "barn-raising" parties where structures and community are created at the same time. Straw is an annually renewable crop, available wherever grain crops are grown. It is indeed a waste product, much of which is currently burned in the field. The thick walls offer superior insulation value when appropriately built. Bales are easy to work with, lightweight and require a minimum of tools. With a natural plaster, straw bale walls "breathe," and together with the sound absorbing qualities, provide a quiet, healthful interior environment. Straw bales can also be combined to great effect with other natural building systems. Straw bales are used either as infill in a post-and-beam structure, or as a load-bearing system where the bales themselves support the weight of the roof. The bale walls are commonly wrapped with stucco netting and plastered with mud, lime-sand or cement plaster. In many cases, the netting has been found to be unnecessary, and plaster is applied directly to the bales. Structural, fire, and moisture tests have been done on the system with great success, leading to easier code approvals. Several insurance companies have insured bale buildings, and bank financing is becoming available. The system is also gaining acceptance with HUD and Fannie Mae, as well as with large home building organizations as Habitat for Humanity. Straw bale construction has a few drawbacks; the walls tend to be "organic" and if not carefully built, can use excessive amounts of plaster. Appropriate bales can sometimes be difficult to locate, and if inadequately stored can be susceptible to damage by rain. Current code restrictions demand "overbuilt" systems which can increase costs, and a contractorbuilt straw bale house can be slightly more expensive than its stick frame counterpart. Straw-bale buildings have been built with code approval in every climate from New Mexico to Minnesota. Because straw bale construction is still so new, innovations are continually being developed. An external pinning system shows great promise, as do the possibilities of vaulted and domed roofs entirely of straw bales. Straw is also being used to create compressed panels to replace plywood and as interior partition walls. Ongoing innovations are recorded in The Last Straw, an essential journal for the field. Thatch The use of reeds, grasses or palm fronds as a roofing material is still common in Europe and many southern countries. This natural roofing material is of increasing interest to builders seeking an alternative to industrial roofing methods. Thatched roofs, if well built, can last up to sixty years or more, and provide a pleasing counterpoint to many of the wall systems mentioned here. Thatch breathes, can use local materials, is highly insulating, and is extremely beautiful. Thatch however, is a highly skilled and time-consuming craft, with only a few practitioners left. This can lead to excessive costs. If a thatched roof is not well built, it will need to be replaced within a few years, and is prone to leaks. Thatch can provide a home for undesirable pests, and fire danger is also a distinct disadvantage for improperly thatched roofs. In many countries in Africa, thatching grass is increasingly rare and expensive, and the desire for "modern" roofs has led to its decline. Wattle and Daub The technique of weaving branches (wattle) as a support for mud plaster (daub) is perhaps the oldest of earthbuilding techniques and is still used for traditional architecture in many parts of the world. Uncommon in the U.S., it can be used in mild climates to create thin earthen walls, but lacks the thermal mass or insulation desirable in other climates. An intriguing use of wattle and daub is to create interior partition walls. Wood Wood is an ideal building material: strong, easily worked and beautiful. Its major disadvantage is that current rates of use are unsustainable, leading to widespread deforestation. Natural builders are seeking alternatives to conventional stick-frame construction where wood is used indiscriminately, and have begun to use wood in new ways. Building with exposed timber-frames surrounded by materials such as straw-clay or straw bales can take advantage of the beauty and structure of wood while eliminating unnecessary use. Innovations in bentwood truss construction in Nova Scotia shows ways to create strong members using smaller diameter trees. Other builders are finding uses for driftwood, and irregularly shaped trees which would otherwise go to waste. Innovative use of scraps and sawdust make the best use of wood for panels, hybrid products, etc. In addition, increased popularity of non-wood construction systems can lead to reduced wood use and ecosystem rehabilitation. Appropriate timber use is closely tied to sustainable forestry practices. Selective cutting can provide ongoing sources of material while saving delicate ecosystems. Using smaller diameter or unmilled lumber can save large old-growth trees, innovative uses of non-traditional species or young, second growth trees can also be an effective strategy. Conclusion Natural building has a bright future. As techniques evolve and more builders, architects and developers employ them, structures which meet human needs while assisting in the healing of the planet will become more common. While many challenges lay ahead, it is still a hopeful and exciting time to be part of this quest to create a sustainable human culture. Natural Building Techniques Straw-Clay Straw-clay (used interchangably with "light clay") is a building material with un properties. It is a very low-impact material, site-made of unprocessed earth and agricultural fiber. In varous forms, straw-&-earth mixtures have a long history o successful use in buildings of many cultures. It is hard, durable, non-toxic, and s structural (self-supporting within reasonable limits). It is both a reasonably good insulator and a thermal storage medium. It accepts natural admixtures such as li oil, casein and prickly pear extract for greater water-resistance and durability. It handles water vapor well in a cold climate, and it is resistant to rot, vermin and Although there are many variations and techniques, the process show here descr light wall construction of about 12 to 20 pounds per cubic foot (325 to 817 kilos meter) with an estimated R-value (a measure of insulating value) of about R-19 .0526 BTU/hr/sq.ft./degree F) for a finished, dry 12" (30 cm) thick wall. Visit our section on the Affordable Natural House for more on our research into straw-clay (left) Clay-rich soil, dry, 'shredded' and ready to mix in the mortar mixer. The process of constructing a straw-clay wall consists of: 1. 2. 3. 4. 5. 6. constructing the formwork mixing the clay slip coating the straw with slip placing and compacting the straw-clay removing the forms finishing the interior and exterior surfaces Mixing the clay slip...by hand Adding slip to the straw Making straw-clay Clay is mixed with water to form slip. Slip can vary in consistency between thin (like cream) and thick (like a milk shake ~~ at least, such comparisons are meaningful in the Dairy State!). We're using a medium thickness here, mixed with an electric mortar mixer with rubber paddle blades. The clay is not a pure potters' clay, but rather simply earth with a high clay content. A bale of wheat straw (preferred for it's strong, waxy stalk) is opened on a plywood mixing floor. Then clay slip is poured over it and , like dressing on a salad, the straw is tossed until it has just a light coating of clay slip. The mixture's readiness is tested by grasping a bunch of straw in the hand. If it sticks together in a clump, the batch is ready to be compacted into the form. Plywood forms can be washed off and reused for floor or roof sheathing. wall formwork ready for straw-clay placing the strawclay in the forms legwork -- compacting the straw-clay The slip-coated straw is then placed into the forms and compacted. Feet are best; for tight spots we use tampers made from short lengths of 2 x 4. Forms are removed immediately after being filled to the top, to avoid surface mildew growth and to allow the new wall to begin drying immedieately. Depending on the season and the climate (wind and relative humidity), full drying of a 12" thick wall may take a month to several months. In the first week or so wheat grass usually sprouts out of the wall until the wall surface dries. removing the form as the wall goes up wheatgrass growing on the new wall The room is usable before plastering. In this sequence of photos, the work is proceeding by hand. However, farm equipment can be used to mix and deliver the straw clay mixture to the forms. These and other means of simple mechanization can dramatically speed up the labor-intensive process.