Stabilized Mud and Mobile Homes
A colleague who is pursuing a master's degree recently circulated a request for information on the evolution of adobe construction in the post World War II era. He was specifically referencing California, but it provoked a review of our experience in New Mexico.
Until the recruitment of young people to the armed forces in the 1940s and their subsequent exodus to take advantage of the educational opportunities offered by the GI Bill, the adobe buildings here were built and maintained by the extended family (homes), and community (churches). The loss of young people led to expediency by the remaining, aging communities that included the pervasive use of Portland cement in place of earth plaster during maintenance cycles. Applied with the best of intentions, we now know it was the kiss of death for many buildings because Portland retains moisture. Fortunately, 40 to 50 years later, the prodigals returned to the communities and inspired a widespread "roots" movement. (It was the cunning perception of this phenomenon that prompted Susan Herter's idea that resulted in the celebrated Cornerstones Community Partnerships program that is still a vital, irreplaceable component in the preservation of our earthen heritage.)
Meanwhile, adobe had become sexy in Santa Fe thanks to architects such as John Gaw Meem, Bill Lumpkins and others, and the "style" became ubiquitous. There was a huge call for adobe bricks, and I very clearly recall my family's home being built with blocks for which my father paid a penny apiece. That was the early 1950s. At about the same time mobile homes, to the horror of many, began to dot the northern New Mexico landscape.
By the mid-seventies, Paul Graham McHenry had popularized the Adobe, Build-It-Yourself trend. I loved the guy, but disagreed with many of his approaches, including his insistence on driving 16d and 20d nails into the adobe for lathing. Paul was also an advocate of stabilized block, and many experiments resulted. Ultimately, Portland was abandoned as a 5% admixture in favor of 12% asphalt emulsion in the mixing water to make fully stabilized adobes, and 6% asphalt emulsion in what are now commonly referred to as stabilized adobes. One of the reasons asphalt is used is to compensate for unsuitable soils. The emulsion replaces clay as a binder.
The logic (misplaced in my view) of a water-resistant, "stabilized" adobe was irresistible to the code writers, and the term not only became part of the lexicon, the technology was applied statutorily.
By the late 1970s, Portland became the standard mortar because it set more quickly than mud, and in any weather, and allowed for more rapid construction. Simultaneously, model energy codes encouraged the use of sprayed-on insulation on the outside.
Then, the final insult, elastomeric plasters became the rage in the early 1990s.
So, our post-war experience is this: Over the course of two generations adobe buildings with earthen plasters were replaced by soil blocks saturated with asphalt emulsion, laid up in Portland cement, tied with a concrete bond beam (replacing the older wood), sprayed with polyurethane foam, lathed with 20d (and larger) nails, and schmeared with latex.
God deliver us. This is not earthen construction; it is a composite with which one could build an adobe submarine.
Nevertheless, I have no doubt that these buildings, just as old mobile homes, will someday come to be appreciated and will comprise their own sub-set in the history of southwestern architecture. Really, I prefer the mobile homes for their honesty and authenticity.