Rammed earth

Rammed earth, also known as taipa (Portuguese), tapial (Spanish), pisé (de terre) (French), and hangtu (Chinese: ; pinyin: hāngtǔ), is a technique for building walls, foundations, and floors using natural raw materials such as earth, chalk, lime or gravel. It is an ancient building method that has seen a revival in recent years as people seek more sustainable building materials and natural building methods.

Rammed-earth can be simple to construct, noncombustible, thermally massive, strong, and durable. However, structures such as walls can be labour-intensive to construct without machinery (powered tampers), and they are susceptible to water damage if inadequately protected or maintained.

Rammed-earth buildings are found on every continent except Antarctica, in a range of environments that include temperate and wet regions, semiarid deserts, mountain areas and the tropics. The availability of useful soil and a building design appropriate for local climatic conditions are the factors that favour its use.

Building a rammed-earth wall involves compressing a damp mixture of earth that has suitable proportions of sand, gravel and clay (sometimes with an added stabilizer) into an externally supported frame or mould, creating either a solid wall of earth or individual blocks. Historically, such additives as lime or animal blood were used to stabilize the material, while modern construction uses lime, cement or asphalt emulsions. Some modern builders also add coloured oxides or other items, such as bottles, tires, or pieces of timber, to add variety to the structure.

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