Dialogos de Edificacao: Rammed Earth
Lisbon, Portugal
1988

taipa/ rammed earth

location
Estremadura, Riba Tejo, Alto Alentejo, Baixo Alentejo, Algarve
materials
Partially clayey raw earth, sometimes with addition of small stones, gravel or vegetal fibres, etc.
characteristics
Construction technique for monolithic inner and outer walls. This technique is based on the use of earth, conveniently humidified, which is rammed by the help of a stick within an immobile mould. In order to receive a material which is hardly affected by the movement of water and which remains highly capable in load-bearing terms, this technique requires a series of attentive steps not to be neglected. Rammed earth requires a foundation to impede the entry of water into the material (through capillaries or directly) and particular care with the roof and the eaves line. In case of lateral loads onto the walls, these need to be reinforced with stone or brick elements. The advantages of this construction system is its thermal insulation capacity. Due to the use of the convenient and cheap material earth and a rapid construction process, this method requires a rather short amount of time to be realised. Currently the main difficulty lies in the amount of specialised manual labor the process asks for.
utensils used
The moulds are named after their respective side planks, which differ according to the function they serve.
exterior cover
plaster and whitewash
interior cover
plaster, stucco and whitewash

constructing a rammed earth wall
1. Choose the earth to be used. Depending on where the material is used, typically the composition differs due to varying components, resulting in certain specificities for each application method. The choice of earth is normally determined by the locality of the construction site and by the “know-how” of the skilled brick masons performing the constructive task. In any case the earth needs to be sandy, rich in gravel and small stones, with a clay component of ideally around 10-20%.
2. After being dug up, the earth is transported on site and is mixed with a hoe, slowly adding the necessary amount of water (or not), depending on the natural humidity it beholds.
3. Working between the two mould planks, two men compress and ram, with the help of rods, the barely humid earth into layers of about 10cm; this compression is executed layer by layer, quite thin, with a necessarily lengthy and strong process. The rods or poles for ramming the earth are wedge-shaped, the ones for smoothing the earth are cylindrical. The earth layers are placed one on top of the next, and get rid of all the possible occurring joints through their heavy and accumulating weight.
4. To complete one piece, the actual length can vary, one removes the side board and in consequence the rest of the mould, to then move it to the consecutive position where the next piece shall be built up, thus shaping the perimeter of the construction.
5. Before beginning a new piece, a band of mortar of clay and sand is applied, running around the edges of the mould. This is used to smoothen the joints of the mould panels, protecting the newly constructed mass from wear and erosion. It is furthermore necessary to tap the holes that planks of the mould leave as a negative.

The thickness of the walls vary from 50cm in one storey houses to 90cm on the ground floor in two storey houses and every row of rammed earth has a height of 50cm. The joints between horizontal consecutive rows are typically kept small by laying heavy stones of 20 or 30cm on top of the walls.

Openings for walls and windows are usually opened after the executed wall is constructed, demolished according to adjacent spaces. The voids can be decorated and in this case the rim of the carpentry work is joint directly to the rammed earth. Or, can alternatively be decorated with brick or quarry stone.

Less frequently, constructions are made with bricks as placeholders for voids. The voids are commonly spanned with wooden rafters. If the facades contain many voids, the brickwork of the wall is typically constructed in stone to avoid a lot of difficult manual labor.

This text was translated by us from the Portuguese book Dialogos de edificaçao, 
published 1998.
The images are taken from Arquitectura Popular em Portugal, published 1988.

Title: Dialogos de edificaçao
Author: Gabriela de Barbosa Teixeira and Margarida da Cunha Belém
Published: 1998, Lisbon
Type: Book
 
Posted: March 2020
Categories: alentejo, architecture, earth, localism, portugal, raw materials, sustainable design, vernacular architecture

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