Adobe. New look at a centuries-old building material

When his search for ``more creative'' work turned Paul McHenry from industrial architecture to adobe design and construction, he knew he had found his lifework. He did not know, however, that his new craft would take him from the wide-open desert, blue skies, and ancient adobe dwellings of New Mexico to China, Algeria, Ecuador, and many other nations. After 25 years of studying, designing, and restoring adobe structures, Mr. McHenry is one of the world's foremost experts on adobe and ``rammed earth'' structures.

The thick, claylike substance McHenry knows so well is a mixture of sand, clay, and aggregate (minerals). Molded into a building block, roughly 12 inches wide, 4 inches deep, and 10 inches long, it is known as ``adobe block.'' Solidly packed into a frame already constructed for a building, then smoothed on the vertical sides, it is known as ``rammed earth'' -- a method often used in wetter climates.

Either way, it is one of the most cost- and energy-efficient as well as sturdiest building materials available to man.

For centuries the Pueblo Indians of the Southwestern United States have dwelt in tiered adobe structures. Spanish governors and missionaries erected adobe palaces and churches throughout the Southwest and Latin America. And kings in northern Africa and Germany built adobe castles, churches, mosques, and homes for the peasants.

Looking anew at its widespread historical use, both private firms and public agencies have begun to recognize that adobe can play a vital role in providing shelter for many of the world's homeless people -- particularly in the third world, where building materials, water, electricity, and other energy sources are scarce or nonexistent. ``The elements needed to produce adobe block or rammed earth structures can be found in all parts of the world,'' McHenry says.

McHenry has been instrumental in the growing worldwide recognition of adobe as an economical building material. According to a colleague: ``Long before adobe became glamorous again in the US, McHenry studied, wrote, sacrificed, begged, and preached to get adobe back into the building scene.''

His first book, ``Adobe, Build It Yourself,'' published in 1973 and revised in 1985, has been one of the all-time best sellers at the University of Arizona Press. During the early 1970s, the US Information Agency considered the book an outstanding text and distributed it throughout the world. McHenry's most recent publication, ``Adobe and Rammed Earth Buildings: Design and Construction'' (John Wiley & Sons), is being used as a textbook for college courses as well as a resource for international symposiums on earth structures.

To meet the challenges of the third world, development agencies are increasingly concentrating on what is known as ``appropriate technology.'' This, according to McHenry, means that the technology being considered to solve a problem is ``economical, doesn't require buying and importing lots of material, and does not require highly skilled people to implement it.'' According to McHenry and other industry experts, the building methods used for adobe meet all three criteria.

Adobe structures are also economical to heat and cool. ``As a high-mass construction material, [adobe] has a great capacity for thermal storage,'' says McHenry. ``Its thermal mass stores and then balances out the highs and lows of the average daily temperature outside.''

``Concrete is also a high-mass construction,'' McHenry adds, ``but the technical elements [sand, gravel, cement] of concrete are not as advantageous as those of adobe for thermal storage.'' So concrete does not store heat as well and requires better insulation.

More important, according to McHenry, are recently discovered insights concerning the energy required to manufacture different building materials. ``How energy-expensive a material is to produce is a measure we seldom look at. We look at the heating and cooling bills. But we pay little attention to the energy costs of manufacture.''

McHenry has been leading the field in considering this neglected aspect of the industry. His studies show that it takes the energy equivalent of one gallon of gasoline to make eight common baked-clay bricks. One adobe brick, roughly four times the size of those eight common bricks, requires less than one-third as much energy to create. McHenry calculates that, ``per 100 square feet of a building, there is a 60-70 percent energy savings in manufacturing if we switch from concrete to adobe.''

``Granted,'' he says, ``the adobe brick won't last quite as long, won't be quite as perfect [in shape] of a material.'' Nevertheless, adobe structures last for centuries. The Taos Pueblo, the oldest continuously inhabited structure in the US, was built more than 900 years ago.

An important aspect of McHenry's work has been documenting the use of adobe and rammed earth structures by many civilizations over thousands of years. Searching throughout North and South America, Africa, Europe, Asia, and the Middle East, McHenry has found examples in each region. This evidence has helped him prove adobe's suitability, availability, and social acceptability.

Although their use was widespread and enduring, adobe and rammed earth went out of style in major construction during the early 1900s, for two reasons: First, because handmade adobe block is very labor-intensive to produce, and second, because of adobe's ``image problem.''

Traditionally, two workers can mix and mold about 300 adobe blocks a day. The drying process for these bricks takes, under the best weather conditions, at least seven days. In winter it can take seven to eight weeks. If the blocks do not dry properly, they will crumble at the slightest touch.

Social acceptability is also a problem in many countries. As McHenry puts it, ``Adobe has had an image problem.'' According to him and other experts on adobe dwellings, adobe has been seen as the housing of the poor. Handmade adobe may be rough, with straw or other debris protruding. This has been perhaps McHenry's greatest obstacle to overcome in helping third-world development agencies recognize the value of building with adobe. It has also been his reason for documenting the use of adobe in a wide variety of dwellings, including a middle-class family's home in Rochester, N.Y.; a castle in Germany; and a king's 800-room palace in Saudi Arabia.

During the last century, however -- particularly in the Middle East -- inner-city adobe dwellings have been bulldozed and replaced with cement-block dwellings -- often lightly stuccoed to give them the same rich adobe color. ``Rightly or wrongly,'' says McHenry, ``cement block is what people all over the world imagine as the greatest.'' As a consequence, ``I think one of the first jobs of government people, ours and the third world's, is to make this solution [building with adobe] acceptable, desirable. It doesn't have to be ugly. It doesn't have to symbolize poverty, and you can get tremendous results with it.''

The newest development in the adobe industry -- a machine that produces up to 600 adobe blocks each hour -- may be just the key to eliminating adobe's social stigma and shortening its labor-intensive manufacturing process. The machine produces blocks that are every bit as symmetrical as cement block and have none of the roughness or debris that make adobe unappealing to some people. According to McHenry, ``It seems to help bridge the gap between the old traditional adobe and the new idea of concrete block.''

The increased demand for his expertise, and the worldwide interest in the adobe-block machines, have assured this earth-structure veteran that his 25 years of toil on adobe's behalf have not been in vain; its acceptability is growing. ``In Mexico, for example, three years ago you'd say `adobe' and they would grimace,'' McHenry says. ``But they have finally come to realize that they have no choice, and they have to work with what they've got.''

While adobe may have a poverty image in some regions of the world, in the Southwestern US it is a prized and expensive building material. The area is dotted with McHenry's work -- homes he and sons Jamie and Bruce have designed and built, and churches, pueblos, and monuments they have restored. At present they are working on a major project to help restore one of New Mexico's most treasured monuments -- Acoma Pueblo's ``Sky City.''

McHenry is convinced that ``people just don't have any choice'' but to use adobe in meeting low-cost housing needs. In his eyes, the earth-structure industry is ``a brand new business that is going to just take off.''

Coming tomorrow: A machine that revolutionizes the use of adobe.