The Great Houses of Chaco Canyon

In Great House architecture, such as Pueblo Bonito, it is clear that there are multiple generations at work. A worker that began young, in the early days of the construction of Pueblo Bonito, did not live to see its completion. The science of dendrochronology (tree-ring dating) has taken much of the guesswork out the beginning and end construction dates. The massive logs used as beams in the Great Houses can be accurately dated to the year they were cut down. One wrinkle that occasionally appears is the Chacoan tendency to remodel, and recycle building materials from past projects. Taking this into consideration, archaeologists work with a high degree of confidence when they discuss dates of construction in Chaco Canyon.

As one views the intricate stonework of these Great Houses, it is hard to imagine that the stonework was not the finished exterior feature. A layer of plaster was applied, or the walls were whitewashed: “For whitewash, the people had used a soft-muddy looking sandstone…Judd and his colleagues did an experiment and learned that [the sandstone] readily disintegrates in water ‘and produces a grayish pigment identical in all outward appearances with that employed by the ancients.”

The intricate masonry seems to be a facade of achievement in and of itself. If the walls were indeed whitewashed, then all of the intricate stonework that awes the modern visitor was not visible to the contemporary Chacoan from 850-1150. Neil Judd and his excavators discovered that the whitewash that the Chacoans used was made of sandstone and applied as a thin coat of plaster for the walls. Imagining the magnificence of Pueblo Bonito whitewashed is difficult. Plus, we’ll never know what type of art or images may have been displayed on this whitewash, if any.

In Pueblo Bonito alone, there are sub-categories to the time periods that can be broken down into five different masonry and veneer styles. These styles vary in the kind of stones used and in the ways they are arranged. Early styles favored hard, dark brown sandstone of uniform size. Later styles used multicolored, softer, tabular stones of greater size and variability. The latest style often incorporated large, soft, yellowish blocks, often ground smooth on the exposed surface.

Both the small houses and Great Houses are constructed out of intricate masonry, adobe, and timber. The timber added a degree of flexibility to the structures, which has likely contributed to helping the buildings resist the literal sands of time. According to Brian Fagan, these structures would have had as much as forty tons of stone in one single room. Three Great Houses (Pueblo Bonito, Una Vida, and Peñasco Blanco) are credited with being the first constructed in Chaco Canyon: They made three buildings large, multi-storied, and arc-shaped (except for a dog-leg at Una Vida mandated by topography). They gave them all remarkably similar floor plans. They created a line of large circular pit structures in the plaza. Behind them they built a row of large ramada-living rooms, a second row of large featureless rooms, and in the rear a third row of smaller storage rooms.

Architecturally, there are numerous similarities between the Great Houses. They have ubiquitous windows and doorways that would have required significant forethought and planning to allow for proper alignment. An intriguing fact about core and veneer masonry is that it is unique to Chaco Canyon, and not found elsewhere in the San Juan Basin prior to Chaco. It is possible that this knowledge and technology was not imported but developed in Chaco Canyon to address the needs of their multistory architecture.

G.B. Cornucopia explains how the veneer was made up of rocks that were chipped from the surrounding sandstone; it cleaves naturally into flat 90° angles. This cleavage made it easy to manipulate and the perfect stone for polished veneer masonry. The core of the wall would be comprised of similar unfinished stone that had been extracted from the same geological level as the veneer. The Chacoans understood rock density and understood that in order to build successfully, densities must remain even throughout construction. This form of core and veneer also created the first insulation, which we know of. As previously mentioned, it proved effective, as there is only a 1° variance between the room and wall temperature inside the structures. These improvements were for more than just structural support alone.