Crossbreeding Plasters: Folly in Every Way
Laziness and short cuts in the restoration or replication of traditional buildings is shortsighted and self-defeating. The most profound lesson learned during the last two decades of research on earthen and wooden buildings is that they embody proven technologies, however simple, that allow buildings to work in a given environment. This has been illustrated many times in the recent past and, fortunately, been well documented; the survival of earthen and timber buildings in Turkey during the earthquakes of 1999 and 2000 is a case in point. Death and destruction reigned in the concrete and steel apartment buildings, while the old and seemingly feeble earthen buildings survived astonishingly well.
Nevertheless, as new products hit the market we succumb to the normal tendency to tinker with even proven methodologies. Readers of this column for the past three years of so have had to endure several soap-box tirades about the gratuitous mixing of modern and traditional materials, usually to the detriment of the latter. Among the more irritating of recent tendencies among architects and builders is to overlay earthen plasters on commercial, hard renders.
I do not know who thought this up, but its now common practice to lath an adobe wall, apply gypsum-based Structolite plaster and then, before it has set, apply a thin coat of mud for appearances only. What a strange concept.
Years ago when I was in the water well business and shopping for state-of-the-art equipment, I came across several drilling rigs that were advertised as hybrid. They combined the proven technology of percussion drilling using a heavy weight at the end of a cable and the more modern method of rotating a string of pipe with a bit at the end. The combination made for an ungainly assemblage that was neither fish nor fowl. To make matters worse, both pneumatic and hydraulic drive systems were becoming widespread and the manufacturers sought to further modernize their rigs by using not one, but both on the same machine. In fact, it was even uglier than that: by operating a switch or lever an electric solenoid activated a pneumatic valve that in turn engaged a hydraulic ram or motor which in turn performed the desired function. Seemingly unable to choose the most effective (to say nothing of simple) system, they stacked them all. I admit to being unbearably smug when the competition bought into those maintenance nightmares while I went for the simplest, most repairable equipment possible.
Mud over Structolite is a folly similar to those stacked technologies. I cringe at the thought of driving nails into adobe, shattering it to the core, to hold up wire mesh. I abhor the whole concept of applying non-vapor-permeable plasters like Structolite over an earthen substrate. And I just lose it when the purity and functionality of an earthen finish is utterly compromised by becoming a purely decorative element. Earth, after all is compatible with earth; there are no adhesion or cohesion issues that need to be addressed with metal lath and bagged compounds.
As I do with most of the arguments I undertake, I'm losing this one. Architects, contractors and code enforcement officials like metal and other rigid objects in buildings that are otherwise, as with adobe, constructed predominantly of soft materials. That choice of materials is the primary debilitating factor in the conservation of both existing earthen buildings, and the fading technologies that should be instructing us how to build new ones.