Ancient Solutions for Monumental Earthen Construction in Mesoamerican Humid Tropics

Earthen architecture without impermeable roofing and foundations is considered unfit for humid environments. This assumption is challenged by archaeological evidence. In Mesoamerica, in the humid tropics, thousands of sites built only of earth are between 1000 and 4000 years old and demonstrate efficient and durable building traditions in an adverse environment. In this article, I address three aspects common to these traditions. Two of them are different from modern conventions and would even be considered inappropriate: the absence of foundations and continuous coatings. The third aspect is related to the use of bitumen as an additive in construction, considered to be a 20th-century invention. I address these aspects as an archaeologist and use comparative stratigraphic studies from Mesoamerican sites of semi-arid and humid climates (from my own excavations and other sites), supported by previous research on construction sample from the La Joya site on the Gulf Coast of Mexico, that includes analysis of composition (granulometry, XRF and XRD, GC-MS), manufacturing process (micromorphology), mechanical properties, and replication experiments. But these cannot fully explain why the buildings lasted for centuries. Therefore, their unconventional construction systems deserve closer attention from conservators, architects and engineers, as they could enrich both heritage conservation and modern construction.