Ancient Solutions for Earthen Architecture in Humid Tropical Environment

[EN] Conventional wisdom considers earthen architecture unsuitable for very humid climates, unless stone foundations and waterproof roofs can be implemented. Archaeological evidence does not always support this assumption. There are thousands of major earthen architecture sites in the humid tropical lowlands of Mesoamerica starting 3000 years ago, using only earth (no stone or lime), that show that it was a preferred and viable technique. This paper addresses three aspects of pre-Columbian construction, derived from 20 years of research in the AD 1 to 1000 archaeological site of La Joya, on the Gulf Coast of Mexico: the absence of foundations, the use of bituminous additives, and the use of continuous surface coatings. These traits appear to have been key factors to ensure the stability of the buildings and the resistance of exposed (unroofed) surfaces for centuries. Interpretation is based on construction systems identified through stratigraphic excavations, chemical analyses (organic and inorganic), and micromorphological study of construction samples, complemented by studies of mineralogical composition and mechanical properties, as well as replication experiments with local clays. These ancient solutions were effective, even though they would probably not be deemed appropriate in conservation or modern construction.