Ch.4: Chacoan Architecture

URBAN GENESIS AT CHACO: Case Study of the Origin of Civilizations. Chapters: 1 2 3 4 5 6

4.9 Concurrent Chacoan Designs

The synchronous development of a few selected sites is shown below. The striking jump in scale of the early great-houses is shown clearly in contrast to three small sites (29SJ 625, 627, 629). The small sites are essentially unit pueblos as described in chapter three.



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Small Sites	Early Great-House	Classic Great-House	Late Great-Houses

Compare the design of new great-houses with contemporary expansions of existing great-houses. Early great-houses such as Una Vida, Peñasco Blanco, or Pueblo Bonito (shown) have curved room-blocks facing south or east onto a plaza. The form of this initial curved room-block was respected during successive expansions of each building. In fact great pains were taken to maintain the formal continuity of Pueblo Bonito: new walls were spliced into existing ones to create a seamless transtition into a new curve with a larger radius.

Classic Phase great-houses begun after AD 980 were designed differently, with a straight double or triple row of rooms forming the room-block. Chetro Ketl, Hungo Pavi, Aztec Ruin, and Pueblo Alto (shown) are examples of this style. Kivas were still located in the public area in front of the room-block, retaining the same formal relationship of pit-structures to room-blocks seen in unit pueblos.

In the Late Classic, great-house design changed again: north-south wings were added to most of the great-houses. By the end of the eleventh century, public spaces were becoming increasingly enclosed as defined plazas. Mid-sized kivas also began to be incorporated into the room-blocks, rather than being set into the ground in the plazas.

Late Phase great-houses, begun after AD 1100, are yet again very different in design. Kin Kletso, Casa Chiquita, and the three shown at right are all Late Phase great-houses. Typically they are smaller, with smaller rooms, no plazas, and all kivas are embedded into the room-blocks. They are barely larger than the largest contemporary dwellings, such as 29SJ395, but they are extremely regular in form. Most, if not all the Late great-houses were built in single construction campaigns wtih a single masonry style throughout.

The sequence of room-block contruction in great-houses and Historic pueblos is fundamentally different. In Historic pueblos, house-blocks were built and occupied in small increments, room-by-room. Party walls were the primary plane of division, and transverse walls, which bore the main roof-beams, were the responsibility of each family. Only a small amount of labor and materials was needed at any given time for incremental expansion.

Great-house room-blocks were preplanned and built at once, whether they were new buildings or additions to existing structures. Lekson (1984) observed that the layout of the foundations may have been used as a design device. Before standing walls could obstruct views, the builders could use line-of-sight surveying to align the foundations with distant landmarks or even celestial alignments (discussed later). After the foundations for a block were laid out, transverse walls were built first, not party walls. The party walls, which divided the block into separate suites, were built last as infill. Therefore most of a room-block was finished before any usable rooms were enclosed.

Chacoan room-blocks were built in big, coordinated building campaigns were not needed to without the investment of a large amount of labor and materials at one time. Not only the regularity and scale, but even the sequence of great-house construction indicates that they were produced by large-scale, highly-coordinated groups, not just families living as neighbors. The different sequence, with transverse walls built first, also serves structural purpose that may be deliberate. As in Historic pueblos, the transverse walls were the main load-bearing walls, carrying the primary roof-beams. The Chacoans built the transverse walls as long, continuous structures. In eleventh century construction, beams were incorporated as intramural stringers to increase the longitudinal strength of the walls. The continuity of transverse walls resisted overturning forces, and the party walls served only as lateral buttresses.

This pattern of construction, along with the decreasing number of domestic features found in great-houses, indicates that these structures were not domestic, but rather a form of public architecture (Windes 1978, Vivian 1990, Judge 1991).