page_title: Rammed earth
section_title: The process
hierarchical_section_title: Rammed earth / The process
caption_attribution_description: Mur en pisé (non stabilisé) dans le Nord-Isère, 2005 Pisé wall(rammed earth, not stabilized)in Nord-Isère, France, 2005
context_page_description: Rammed earth, also known as taipa in Portuguese, tapial or tapia in Spanish, pisé in French, and hāngtǔ in Chinese, is a technique for constructing foundations, floors, and walls using natural raw materials such as earth, chalk, lime, or gravel. It is an ancient method that has been revived recently as a sustainable building method.
  Edifices formed of rammed earth are on every continent except Antarctica, in a range of environments including temperate, wet, semiarid desert, montane, and tropical regions. The availability of suitable soil and a building design appropriate for local climatic conditions are the factors that favour its use.
context_section_description: Making rammed earth involves compacting a damp mixture of sub soil that has suitable proportions of sand, gravel, clay, and stabilizer, if any into a formwork (an externally supported frame or mold).
  Historically, additives such as lime or animal blood were used to stabilize it.
  Soil mix is poured into the formwork to a depth of 10 to 25 cm (4 to 10 in) and then compacted to approximately 50% of its original volume. The soil is compacted iteratively, in batches or courses, so as to gradually erect the wall up to the top of the formwork. Tamping was historically manual with a long ramming pole, and was very laborious, but modern construction can be made less so by employing pneumatically powered tampers.
  After a wall is complete, it is sufficiently strong to immediately remove the formwork. This is necessary if a surface texture is to be applied, e.g., by wire brushing, carving, or mold impression, because the walls become too hard to work after approximately one hour. The compressive strength of rammed earth increases as it cures. Cement stabilised rammed earth is cured for a minimum period of 28 days.
  In modern rammed earth buildings, the walls are constructed on top of conventional footings or a reinforced concrete slab base.
  The construction of an entire wall begins with a temporary frame, denominated the "formwork", which is usually made of wood or plywood, as a mold for the desired shape and dimensions of each section of wall. The form must be durable and well braced, and the two opposing faces must be clamped together to prevent bulging or deformation caused by the large compressing forces. Formwork plays an important role in building rammed earth walls. Historically, wooden planks tied using rope were used to build walls. Modern builders use plywood and/or steel to build formwork.
caption: Old rammed-earth wall with deterioration, in France
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