Ancient Roots

Because of its versatility and widespread availability, earth has been used as a construction material on every continent and in every age. It is one of the oldest building materials on the planet; the first freestanding human dwellings may have been built of sod or wattle-and-daub. About 10,000 years ago, the residents of Jericho were using oval, hand formed, sun dried bricks (adobes), which were probably a refinement of earlier cob. Even today, it is estimated that between a third and a half of the world’s population lives in earthen dwellings.

Earth construction takes many forms, including adobe, sod, rammed earth, straw-clay, and wattle-and-daub. “Cob” is the English term for mud building, which uses no forms, no bricks, and no wooden structures. Similar forms of mud building are endemic throughout Western and Central Europe, the Ukraine, the Middle East and the Arabian peninsula, India, China, the Sahel and equatorial Africa, and the American Southwest.

Exactly when and how cob building first arose in England remains uncertain, but it is known that cob houses were being built there by the 13th Century. Cob may have evolved from earlier techniques like wattle-and-daub, where mud is plastered over a framework of woven branches. One possibility is that, originally, mud was used as an intermediate filling between double wattle walls, and that when the wattle decayed, it was found that the building remained sound without it. Another theory holds that cob evolved from the mud mixture used almost universally in Medieval times to mortar stone walls and to fill the cavity between two stone faces. When the valuable facing stones were pirated or fell away, cob walls remained.

However it happened, cob houses became the norm in many parts of Britain by the 15th Century, and stayed that way until industrialization and cheap transportation made brick popular in the late 1800s. Cob was particularly common in Southwestern England and Wales, where the subsoil was a sandy clay, and other building materials, like stone and wood, were scarce. English cob was made of clay-based subsoil mixed with straw, water, and sometimes sand or crushed shale or flint. The percentage of clay in the mix ranged from 3 percent to 20 percent, with an average of 5-6 percent working well. It was mixed either by people, shoveling and stomping, or by heavy animals such as oxen trampling it.

The stiff mud mixture was usually shoveled with a cob fork onto a stone foundation, and trodden into place by workmen on the walls. In a single day, a course or “lift” of cob would be placed on the wall between 6 inches and 3 feet high, but usually averaging 18 inches. It would be left to dry as long as two weeks before the next lift was added. Sometimes additional straw was trod into the top of each lift. As they dried, the walls were trimmed back substantially with a paring iron, leaving them straight and plumb, and commonly between 20 inches and 36 inches thick. In this way, cob walls were built as high as 23 feet, but usually much less. Openings for doors and windows were either built in as the wall grew, or else lintels of stone or wood were set into the wall at appropriate heights and the openings carved out after the cob had settled and dried.

Many cob cottages were built by poor tenant farmers and laborers, often working cooperatively. A team of a few men, working together one day a week, could complete a house in one season. A cottage begun in the spring would receive its thatch roof and interior whitewash in the fall, and its inhabitants would move inside before winter. Often they waited until the following year to plaster the outside with lime-sand stucco so that the walls would have ample time to dry. Cob barns and other outbuildings were sometimes left unplastered.

But cob buildings were not reserved solely for the humble peasants. Many townhouses and large manors, built of cob before fired brick became readily available, survive in excellent condition today. Among them is Hayes Barton, the birthplace of Sir Walter Raleigh, who had so much affection for his childhood home that he offered to buy it from its then owner for “whatsoever in your conscience you shall deme it worth.” An estimated 20,000 cob homes and as many outbuildings remain in use in the county of Devon alone. It was common for well-built cob homes to go for a hundred years without needing repair.

British settlers to other parts of the world took the technique of cob with them, transplanting it in Australasia and North America. Early colonists of New Zealand found the clay soil and tussock grass common on the South Island to make excellent cob, and constructed at least 8,000 houses there, of which several hundred survive today. Cob was less popular in Australia, where mud bricks and rammed earth were the preferred earth building techniques, but a few cob buildings survive in New South Wales, in Queensland, and in the vicinity of Melbourne. Cob buildings in North America dating from the same era are few and far between, but include a house built in 1836 in Penfield, New York, and a church in Toronto.

By late last century, cob building in England, considered primitive and backward, was declining in popularity. During the 20th century, however, public attitudes slowly evolved until traditional cob cottages with their thatched roofs are now valued as historical and picturesque. As there was virtually no new cob construction in England between WWI and the 1980s, traditional builders took much of their specialized knowledge with them to the grave. But enough information survived to allow a cob building revival in the 90s, fueled largely by historical interest and the real estate value of historic cob homes.

The English Cob Revival

The English place great value on tradition, and take good care of their historical buildings. In recent decades many long-neglected cob homes have needed repair, causing a resurgence of interest in traditional building techniques. The people involved in the restoration of ancient cob buildings have become the greatest advocates for the reintroduction of cob as a current building technique. The first new construction project of the English cob revival was a bus shelter built by restorationist Alfred Howard in 1978. Since then there has been an increase of new cob built in England, particularly in Devon. Kevin McCabe received a lot of press in 1994 for his two-story, four bedroom cob house, the first new cob residence to be built in England in perhaps 70 years.

The building technique of these revivalists closely resembles that of their ancestors. They mix Devon’s sandy clay subsoil with water and straw and fork the mixture onto the wall, treading it in place. Walls are generally 24 inches thick and straight, applied in lifts up to 18 inches high. The machine age has altered the traditional process in only minor ways: McCabe and others use a tractor rather than oxen for mixing cob, and often amend the subsoil with sand or “shillet,” a fine gravel of crushed shale, to reduce shrinkage and cracking.

In addition to construction and repair, there is a fair amount of research going into English cob. Alfred Howard, for example, has built experimental walls using a variety of subsoils. Larry Keefe, a former building conservation officer, has catalogued hundreds of old cob buildings and become an expert on why cob walls succeed and why they don’t. Larry is the co-founder of a unique program at Plymouth University called “Out of Earth,” dedicated to furthering earth architecture, which has sponsored earth building workshops and several international conferences on earth building.

The Development of “Oregon Cob”

Concurrent with the renewed interest in cob in England, there has been a parallel revival in the United States, led by the Cob Cottage Company in Western Oregon. With less access to (and less dependence on) traditional knowledge, the building system that has arisen here is sufficiently distinct from British cob that it merits a separate name, “Oregon Cob.”

By 1989, Cob Cottage Company founders Ianto Evans and Linda Smiley recognized the need for inexpensive, healthy, bioregional housing. Ianto grew up surrounded by cob in Wales, and later witnessed earthen construction in Africa and Latin America. They were particularly interested in earthen building because of their experience developing and promoting Lorena stoves (fuel-efficient cookstoves molded from packed sand and clay). Experimenting with earthen building in rainy Western Oregon, Ianto and Linda chose British cob as a model because of its demonstrated durability in a cold, extremely wet climate.

When they started their first cob structure, Ianto and Linda were unable to locate anybody with first-hand experience. They relied entirely on their explorations of existing cob structures in Britain and a very sparse literature on the subject, much of it inaccurate and contradictory. The system they developed involved making loaves of stiff mud, called “cobs.” This loaf system had at times been used in Britain (“cob” itself is an Old English word for loaf) as well as in Germany, France, North Yemen, and the American Southwest. Its advantages are that the mix can be made at some distance from the wall and easily transported by tossing the cobs from person to person like a bucket brigade. As construction progresses, cobs can be thrown to a builder much higher on the wall than a pitchfork can be raised.

Another way in which Oregon cob differs from traditional cob is in the attention given to the quality of ingredients and to the proportions of the mix. While cob builders in previous centuries had to use whatever soil was on hand with little or no amendment, we can now cheaply import as much sand or clay as is necessary to make the hardest, most stable mixture. Furthermore, whereas grain straw was formerly a valuable resource for animal bedding, thatching and the like, it is now an underutilized waste product available in huge quantities for little cost. Oregon cob is characterized by both a high proportion of coarse sand and lots of long, strong straw.

Better ingredients, more precise proportions, and thorough mixing allow the construction of stronger, narrower, and more sculptural walls. Using Oregon cob, exterior walls are typically between 12 inches and 20 inches thick; non load-bearing partitions taper to as little as 4 inches (but more commonly 8 inches). Most Oregon cob buildings have curved walls, niches and nooks, arched windows and doorways. By adding extra straw in the needed direction, The Cob Cottage Company developed a system for corbelling arches, vaults, and projecting shelves, beyond the capability of traditional cob.

After inhabiting their first cob cottage for four years and finding it well suited to Pacific Northwest conditions, Ianto and Linda were ready to share their experience with others. I joined them in 1993, when the Cob Cottage Company was formed and the first workshops taught. Since then, we have taught over 60 workshops, mostly week-long, throughout the Western States and Canada. We have also worked in Australia, New Zealand, Mexico, and Denmark. We have trained at least 700 people in cob construction, some of whom have gone on to build homes for themselves or teach workshops of their own. Increasingly, we have made alliances with other natural builders, and a system of hybrid natural building is emerging which utilizes cob for its best qualities in combination with stone (for foundations and thermal mass), lime putty (for plasters, mortar, and whitewash), straw (in bales or straw/clay insulation, as well as in plasters), wood (including unmilled roundwood, for roofs and other structural elements) and many other natural materials.

Cob is well suited to a sensitive house design process, based on careful observation of the site, and placement with respect to slope, microclimate, and ecology. It offers exceptionally flexible opportunities for passive solar heating/cooling strategies. Rather than the industrial geometry of straight lines and right angles, cob buildings can use organic continuous curves, variable wall widths and structural buttresses. Ianto Evans has pioneered space-saving designs which reduce building size and cost, including built-in perimeter furniture, personalized spaces to enclose particular activities, and the sculpting of volumes rather than areas. We have observed that curvilinear spaces are perceived as much larger than rectangular ones with the same measured area. The experience of living in these buildings stretches our ideas of what’s possible with ecological building.

Future Trends

The cob revival is still in its infancy. Every year we learn more: how to improve our efficiency at mixing and building, how to use a wider range of soil types, and new applications, techniques, and designs. It is impossible to predict what direction the cob building revival will take in the years to come, but a few general trends and issues are likely to remain prominent:

First, as more and more cob homes are built in diverse climatic, geographic, and cultural conditions, the technique is likely to become increasingly regionally diverse. For example, strategies will be developed where it is necessary to deal with earthquakes, extremely cold winters, and the unavailability of good quality sand and straw. Just as traditional Welsh cob differed in many specifics from that in Devon and from “torchis” in France, one would expect that eventually cob homes in Texas will both look different and be constructed differently from those in Oregon or Massachusetts.

Second, there will be increasing interest and pressure to bring cob into the building “mainstream,” both in the United States and elsewhere. This will not be as easy as with strawbale or rammed earth, since cob represents a greater departure from conventional industrial building practices. There may be attempts to further mechanize the mixing process, to use forms, or to add unnatural stabilizers like cement or asphalt to the mix. Eventually, some kind of cob building code is likely to be adopted, but whether cob will continue to be as owner/builder friendly remains to be seen.

Finally, the increasing collaboration between natural builders during the last few years points to the development of an integrated natural building system of which cob is only a part. Expect to see more hybrid buildings incorporating earth, straw, wood, stone, and other natural materials. Hopefully this will place less emphasis on individual materials and techniques and more on finding the best, most sustainable solution to regional building situations using the natural materials that are close at hand.

The lessons from cob building have been surprising in their abundance and profundity, yet clearly we are only beginning to learn, and should record more carefully what we do learn. Demonstration structures, particularly houses, should be monitored and analyzed. Much more could be published, particularly about the psychological and spiritual effects of natural buildings. We should acknowledge that cob building is more than a cheap, environmentally benign way to build. It can be a significant tool for the development of a more sane and sustainable culture.

Michael Smith was a founding director of the Cob Cottage Company. He is the author of The Cobber’s Companion and teaches natural building and permaculture throughout the western United States, Canada and Mexico. His also a founder and three-time organizer of the Natural Building Colloquia.

What is Natural Building?

Natural building is any building system which places the highest value on social and environmental sustainability. It assumes the need to minimize the environmental impact of our housing and other building needs while providing healthy, beautiful, comfortable and spiritually-uplifting homes for everyone. Natural builders emphasize simple, easy-to-learn techniques based on locally-available, renewable resources. These systems rely heavily on human labor and creativity instead of on capital, high technology and specialized skills.

Natural building is necessarily regional and idiosyncratic. There are no “right” answers, no universally appropriate materials, no standard designs. Everything depends on local ecology, geology and climate, on the character of the particular building site, and on the needs and personalities of the builders and users. This works best if the designers, the builders, the owners and the inhabitants are the same people. Natural building is personally empowering because it teaches that everyone has or can easily acquire the skills they need to build their own home.

Natural building is not a new idea. In many parts of the world, almost all building still conforms to these criteria. Until the Industrial Revolution, the advent of cheap transportation, and the professionalization of building and architecture, the same was true throughout Europe and America. Pioneer families in the United States built their own homes out of local materials, as the First Peoples here and everywhere always have. Our modern building industry with its resource-extractive, energy- and capital-intensive, toxic, and inaccessible practices must be seen as a temporary deviation from this norm. Let’s look at some of natural building’s many advantages over conventional modern building practices.

Environmental Impact

It’s no secret that the global ecosystem is ill. The housing industry is a major contributor to the problem. Here in the Northwest we see the evidence all around us; the trail from clear-cut to sawmill to building site is easy to follow. Other major modern building components depend on destructive mining: gypsum for sheet rock; iron for hardware, rebar and roofing; lime and other minerals for cement. Every material used in a typical modern building is the product of energy-intensive processing. The mills which saw our lumber, the factories which make plywood and chipboard, the foundries which make steel, the plants which turn natural minerals into cement by subjecting them to enormous heat, all consume vast quantities of power, supplied either by the combustion of coal and oil, the damming of rivers, or the splitting of atoms.

These manufacturing processes also release toxic effluent into the water and hazardous chemicals into the air. The manufacture of Portland cement, for example, is responsible for an estimated 4% of greenhouse gasses. And even after our building materials are made, modern construction depends on an endless stream of polluting trucks to deliver them to us, usually from hundreds of miles away.

In contrast, straw and other materials favored by natural builders are biological by-products which would otherwise create a disposal problem. Enough straw was wasted each year in California alone to build tens of thousands of family homes. Until recently, nearly all the straw produced in California was burned in the fields, but clean air legislation has outlawed that practice. Faced with the problem of what to do with all the straw they can no longer burn, California rice growers have thrown their significant political clout behind legalizing straw-bale building, with the result that the state of California drafted and adopted straw-bale building guidelines.

Of course, it’s impossible to build a house with no environmental impact, but it’s our responsibility to minimize and localize the damage. Digging a hole in your yard for clay to make a cob house may look ugly at first, but it’s a lot less ugly than strip mines, giant factories and superhighways. Nature has enormous capacity to heal small wounds; that hole in your yard would make an excellent frog pond. Many of us religiously protect the trees on our property, then go to the lumber yard to purchase the products of wholesale clear cutting. If we choose to build with wood, it seems a lot less hypocritical to take down a few select trees near our homesites and run them through a small portable mill, or thin overcrowded woodlands of small-diameter poles and build with those. Keeping our environmental footprint under our noses helps ensure that we will minimize our impact and protect the health of our local ecosystems, since we see them from our windows and walk through them every day. Building with natural, local materials also reduces our dependence on the polluting and energy-intensive manufacturing and transport industries.

Human Health

Many of the most fervent supporters of natural building are people with acquired chemical sensitivities and other environmental illnesses. These people are particularly aware of how modern buildings make us sick, but we all know it. Even the mainstream press carries frequent stories of cancers and respiratory problems linked to formaldehyde-based glues, plastics, paints, asbestos, and fiberglass, to name a few favorite culprits. The toxicity of these materials impacts everyone associated with them: the workers in the factories and warehouses, the builders on the construction site, and the inhabitants of the poisonous end products. Natural materials like stone, wood, straw and earth, on the other hand, are not only non-toxic, they are life-enhancing. Clay, one of the most useful natural building materials, is also prized for its ability to absorb toxins and restore health. Natural healing traditions rely on it heavily, for both internal and external applications.

There is increasing evidence that modern buildings also compromise our psychological and emotional health. Right angles, flat surfaces that are all one color, and constant uniformity don’t exist in the natural world where our ancestors evolved. They may trigger a subconscious reaction which tells us “there’s something wrong here,” keeping us continuously nervous and stressed. Most modern homes certainly don’t stimulate our senses with the variety of patterns, shapes, textures, smells and sounds that our pre-industrial ancestors experienced. The uniformity of our environments may contribute to our addiction to sensory stimulation through drugs and electronic media.

Apart from that, there is a good feeling we get from natural buildings which is difficult to describe. Even though conditioned to prefer the new, the shiny, and the precise, we respond at a deep level to unprocessed materials, to idiosyncrasy, and to the personal thought and care expressed in craftsmanship. Nearly all the natural buildings I have seen, regardless of the level of expertise of the builders, are remarkably beautiful. Living in a hand-crafted cob house, I grew to expect the looks of mesmerized awe I saw on the faces of first-time visitors, and the difficulty they had prying themselves from the warm earthen benches when it was time to leave.

Social Justice

Modern building is a big-money industry, with all the problems associated with other industries. In the race to maximize immediate profit, long-term concerns like the health of the environment and its inhabitants are often overlooked. The rich and powerful are able to make their own homes and lives pleasant at the expense of those less privileged, often far away in distant countries. Furthermore, the building industry and regulations concentrate power in the hands of the government and selected corporations, by enforcing compliance with a limited set of options. If the code says we have to use concrete foundations on every building, just think how much money the cement manufacturers will make!

We grow up being told you can’t build a house unless you’re a professional builder. If we want a house, we have to work full-time at a job we usually dislike to make enough money to pay a builder who probably hates his job, too. Since we’re convinced we need to spend $150,000 on a 2000 square foot house, we chain ourselves to a thirty-year mortgage which forces us to keep working at unsatisfying jobs for the rest of our lives.

But it doesn’t have to be that way. By using local, unprocessed materials like earth and straw, building smaller than the conventional house, and providing much of the labor yourself, you can create a home that is almost unbelievably affordable. As the price tag drops from hundreds of thousands to tens of thousands or even a few thousand dollars, it becomes easier to shrug off the yoke of loans and mortgages. You can also save yourself money in the long run with a smaller, more efficient house that uses simple passive solar technology for heating and cooling. As a result you may find your cash needs dropping. You can cut down the hours you work and spend more time with the kids, or grow a big vegetable garden which will save you even more money.

Techniques which rely on human labor and creativity produce a different social dynamic than those which depend on heavily processed materials, expensive machines, and specialized skills. When you build with straw bales, cob, adobe, or rammed earth, the whole family can get involved. A building site free of power tools is a safe and supportive environment for children to learn valuable skills. Or invite your friends and neighbors for an old-fashioned barn raising. Offer them food and an education in exchange for their time and energy. It’s a good deal for everyone, and a lot of fun. While building your home you’re also building a different kind of social structure where people depend on themselves and each other to get their basic needs met, instead of handing over their power to governments, corporations and professionals. When those of us who are relatively affluent use a smaller share of the Earth’s resources, more becomes available to the less privileged and to future generations.

The Natural Building Resurgence

For all these reasons and other personal ones, some individuals have always challenged the modern building industry paradigm, preferring to build for themselves using local materials and traditional techniques. During the back-to-the-land movement of the 1960s and 70s, thousands of people found themselves desiring to build their own homes from available resources, without professional assistance, without much training or money. They were inspired and aided by the example and writings of contemporary pioneers like Helen and Scott Nearing (Living the Good Life, etc.) and Ken Kern (The Owner-Built Home, etc.) The energy crisis of the mid-70s focused public attention on our use of natural resources and on the energy-efficiency of our buildings. At that time a huge amount of research and writing was done on passive solar building, alternative energy systems, and sustainable resource use, much of which was subsequently swept away by government policy and public apathy during the 80s.

Although no longer receiving much popular press, the experimental work of conservation-minded builders continued throughout this period. In the late 1980s, a flurry of activity surrounded the rediscovery in the Southwestern United States of straw-bale building, a technique which had risen to brief popularity in Nebraska in the early part of this century. In Tucson, Matts Myrhman and Judy Knox started Out On Bale, an organization devoted to popularizing this elegant and inexpensive construction system. Around the same time, Ianto Evans and Linda Smiley, inspired by the centuries-old earthen homes in Britain, built their first cob cottage in Western Oregon. The interest generated by this wood-free wall building technique, which had proven itself well-suited to cool rainy climates, led them to found The Cob Cottage Company.

Meanwhile, Iowa-based Robert Laporte had combined the traditional techniques of timber framing from Japan and Europe with straw-clay, an insulating infill of clay-coated straw from Germany, and was teaching his natural-house building workshops across the United States and beyond. Persian architect Nader Khalili had established Cal-Earth, a center in Southern California devoted to developing, educating about, and gaining code acceptance for earth building systems. Also in California, David Easton was building and writing about monolithic rammed earth walls, while others experimented with compressed earth blocks.

By the early 1990s, there were dozens of individuals and small organizations in the United States researching, adapting, and promoting traditional building systems. These visionaries proceeded with their work independently, largely unaware of the existence of the others. Then as the straw-bale boom in the Southwest took off, attracting the interest of national periodicals like The New York Times, National Geographic, and Fine Homebuilding, and as increasing numbers of natural building workshops were offered and people were trained, the “experts” began to hear about and meet one another.

In 1994, The Cob Cottage Company organized the first “Alternative Building Colloquium,” inviting natural builders and teachers from around the country to spend a week together in Oregon. The idea was for these leaders to get to know each other, to share the building techniques they knew best, and to begin to join their various philosophies and experiences into a more cohesive system of knowledge. During that gathering, and the six Natural Building Colloquia which have followed in New Mexico, California, Maryland and Oregon, workshops were given on wall-building systems ranging from adobe to wattle-and daub, roofing techniques like sod and thatch, and foundation systems including rubble trench, dry stone, and rammed-earth bags. Lectures and slide presentations filled the heads of all those present with information on recycled materials, designing with natural forces, bamboo, greywater systems, co-housing, creating sacred space, structural testing and building codes, composting toilets, architectural education reform, steam generation, and a hundred other topics. Traditional yurts, timber-framed structures and straw-bale vaults sprang up and were decorated with multi-colored clays. Ideas and techniques collided and merged, coalescing into hybrid structures including a straw-bale-and-cob dome, and a straw-bale/cob/clay-straw/wattle-and-daub cottage on a stone and earth bag foundation.

Out of these Colloquia and the numerous other gatherings and collaborations of people interested in natural building, a few things have become clear. One, that we are all working together. Even though we may have chosen to focus on different techniques or aspects of natural building, we are all motivated by the same concerns and our personal experience makes up part of a consistent larger body of knowledge. Two, that we are not alone. As word gets out to the greater public, we find enormous interest and support from a growing community of owner-builders, professional builders and designers, activists, educators, writers, and conservationists. And three, that together we hold a great deal of power. The power in our ideas and collective action is capable of influencing the way our society thinks, talks, and acts regarding building and resource use. We are helping to create a society where some day, natural building will again be the norm in the United States as it still is in much of the world, and where a new cob house with a thatched roof in any American town will draw only an appreciative nod.

Michael Smith was a founding director of the Cob Cottage Company. He teaches natural building and permaculture throughout the western United States, Canada and Mexico. He is also a founder and organizer of the Natural Building Colloquium.