Modified Sehalian Scaffolding in the New World?
When adobe buildings are stripped of their plaster and the raw bricks are revealed, an opportunity is presented to glimpse the methods of solving some of the technical barriers faced by the vernacular architects who built them. Unusual bonding patterns in lower courses may have compensated for adobes that were found to have poor compressive strength. Wooden members or "ties" may be revealed that at the time of construction had only a vague purpose but derive from another time and place where those elements may have functioned as seismic arresters. Sometimes, strange and seemingly inexplicable features emerge that haunt the architect, preservationist or historian until they can be assigned a reasonable function. This was the case at the Capilla de San Antonio in Chacón, New Mexico when the cement plaster was removed.
At the beginning of the preservation effort when the adobe walls of the adobe church were revealed, an unusual feature appeared at each corner: 5-1/2 to 7 feet above grade, and in line with the plane of the interior wall surface was a single 3- to 4-inch diameter cedar or oak viga, or rough-hewn pole. The ends were sawn or axe-chopped flush with the face of the wall. Similar poles were embedded at similar heights above grade on either side of the windows in the walls of the nave. In several instances, where investigation was carried out, the poles were found to penetrate the full thickness of the walls. One of them was removed and found not mortised, nailed or tied to anything embedded in the wall. The phenomenon of the poles was recorded and placed in the category of "technology to haunt."
During a subsequent dismantling of a collapsed wall at the San José Mission in Upper Rociada, New Mexico, identical poles were noted. They were found again in the massive walls of the San Rafael church in La Cueva. Here, the eave height is 16 to 18 feet from a variable grade, and the mysterious poles appeared at two horizontal planes in the walls; at roughly the 7-foot level and again at the 12- to 14-foot level. It was seeing them in two levels on what amounts to a two-storey building that sparked my hypothesis that the poles represent a modified version of Sehalian scaffolding.
Many of the multi-storey vernacular earthen buildings in West Africa bristle with protrusions of sticks that comprise a permanent scaffolding to facilitate annual re-muddings. Among the finest examples are the mosques in Djenné, Mali, and Bobo Diolasso, Burkina Faso. The young men who do the plastering step from stick to stick to do their work, rather than spanning the intervening spaces with catwalks.
I conjecture that in New Mexico the poles, protruding perhaps 18 to 24 inches on both sides, provided scaffolding supports during the building process. Planks on either side, counterbalanced with a load of adobes would have provided solid footing and a convenient staging platform. As the wall grew and the poles were embedded, the need for the counterweights would have been relieved. When the walls were finished, plastering would have begun from the top down. When the scaffolding was no longer needed to reach the high areas, the poles were sawn or chopped off and covered with mud.
It is interesting to speculate that the traditions of West Africa have a link with the churches in the Mora Valley of New Mexico. Though there are examples of the use of earthen bricks in the pre-Columbian Americas, the tradition of sun-dried bricks really came to us from the Middle East, via north Africa, to Spain and then northwards from the Iberian colonies in central Mexico.
For further information on Sehalian scaffolding see Spectacular Vernacular by Jean-Louis Bourgeois and Carollee Pelos. Published by Aperture Foundation, New York, 1989.