An Overview of Natural Building Techniques JOSEPH F. KENNEDY Introduction Over the past several decades, numerous vernacular building methods have been investigated and, in some cases, revived and improved upon by a new breed of visionary designer-builder. These techniques are often grouped under the label "natural building," a building philosophy that relies on materials and techniques which are ecologically sound, culturally sensitive, reliant on local resources and skills, and are within economic reach of local inhabitants, many of whom cannot currently afford shelter. Natural building has emerged as a response to an increasing concern for our built environment. Natural materials are an alternative to toxic substances which have led to widespread environmental illness. Those seeking to simplify their lives can build their own homes using such techniques, with community help and local, inexpensive materials. Those who recognize the environmental, social and economic costs of our current ways of construction believe that natural building provides part of the solution to the complex worldwide problem of sustainable living. While interest in natural building has surged in the Industrialized West, many ancient roots have been lost in traditional areas in favor of capital- and energy-intensive industrial building methods. In the name of "progress," crucial cultural and technological riches continue to be abandoned for concrete blocks, tin shacks and other degraded symbols of an untenable Western dream. Ironically, some builders in industrialized countries are now turning to these very cultures for solutions to their building problems. It is to be hoped that a resurgence of interest and research into vernacular building systems will increase respect for these timeless ideas in their native lands. And through diligent efforts, many of these techniques are indeed being revived, studied and implemented throughout the world. Though often appropriate in their original contexts, many ancient techniques are benefiting from scientific and engineering study, creating applications for a variety of new situations. These techniques are being validated by modern structural and other code tests, which also point out directions for further research and improvement. Adobe Adobes are sun-dried mud bricks stacked with a mud mortar to create thick-walled structures. These thick earthen walls provide what is known as "thermal mass" which helps to modulate interior temperatures by absorbing excess heat during the day and slowly releasing it at night. (In chilly climates, thermal mass needs to be insulated to prevent creating a net heat loss in winter.) The use of adobes dates back centuries in traditional earth-building areas such as North Africa, the Middle East, South America and the United States Southwest. While in some areas this building method is in decline, it is still in widespread use in others. Dramatic examples of vaulted and domed structures built entirely of earth bricks still stand after centuries in the Middle East, testament to adobe's timeless beauty and structural integrity. While in "developing" countries 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 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 removed either immediately or after the brick has partially dried. Adobes can take an infinite number of shapes and sizes which are utilized for specific techniques (i.e. small flat square bricks used to build leaning arches and domes in Iran). 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 can also be used. Various stabilizers for the adobes themselves have been developed, with most, however, relying on cement or asphalt-based compounds. While adobe is widely appropriate, precautions must be taken to ensure the durability of construction. Wide eaves are often necessary to protect the walls from rain and foundations must protect the walls from ground moisture, while gutters are used to prevent splashing. Mud plaster is traditionally used to finish adobe structures, only requiring replenishment every few years if the walls are unprotected. Cement stucco has also been used in an effort to provide longer-lasting exterior 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 often hides this damage, buildings can collapse before anything is sensed to be wrong. In addition, indoor water vapor cannot escape fast enough and builds up on the inside of cement stucco, eroding the wall. Because of this, there has been a return to traditional plasters using mud, straw and other natural materials. Because the mortar can be a "weak link" in adobe construction, building codes typically place severe restrictions on it. While other, monolithic techniques, such as cob and rammed earth may fare better in earthquake- prone areas, these, along with adobe are essentially limited to the desert Southwest. Bamboo Bamboo is the largest of the grass family of plants. 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, lack of knowledge of traditional techniques, and because there are so few native species. 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 on these continents, bamboo is often used, as the west uses wood and steel, for structural purposes. It can replace rebar in certain concrete applications, be used 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 also be dangerous however, as indiscriminate cropping can decimate stands and endanger interdependent ecosystems. To address this danger, efforts to create sustainable growing programs similar to those for tropical hardwoods are in development. Cob Cob is an ancient technique of building monolithic (meaning "all one piece") walls using "cobs" of moist earth and straw that has similar thermal properties to adobe and rammed earth. It is being rediscovered as a multifaceted building material applicable to a number of conditions. Virtually unknown in North America, cob was reintroduced by Welsh architect and permaculturist Ianto Evans, who started the "Cob Cottage Company" with his wife Linda Smiley after intense interest in his $500 self- built cob home. A sculptural technique which lends itself to curved organic shapes, cob requires minimal tools and can be built by young and old alike. "Oregon cob" is quite a different process than traditional methods, improving some aspects of the technique through increased attention to design, materials selection and application procedures. The process of building with cob entails mixing local subsoil 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 can be tossed to the builder on the wall who mashes them together to form a monolithic wall on top of a stone or concrete foundation. Cob can also be forked as a mass onto the wall, then shaped into the next layer. The relatively thick walls (they have been known to be up to six feet thick) proceed in layers or "lifts" from 6" to 18" high. Attempts to build higher than this can result in slumping. 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 currently advocated 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, but now several isolated projects are receiving permits. Traditional cob construction is undergoing a revival in England as well, where proponents are rediscovering five hundred year old houses in perfect condition, and new projects are reinvigorated this nearly-lost craft. 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 fuel- powered machines, on the other hand, can produce thousands of bricks in a day.