It's no secret that adobe is one of the most widely utilized materials in construction. For centuries, it has been the go-to material for civilizations worldwide thanks to its aesthetic qualities and durability. Today, we continue using earthen materials like adobe for a wide array of building projects; however, to obtain optimal results, one cannot ignore the art and skill required in brickmaking. For many in the trade, it's a craft that has been passed down generation after generation.
Adobe is a practical and cost-effective resource in building, thanks to its easy sourcing and no-frills application. Observed in the context of sustainable building, these benefits amplify when considering their environmental, social, and economic advantages.
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The structural possibilities of adobe in construction:
Observing ourselves and our surroundings can be a major source of inspiration when it comes to designing our living spaces. For most of natural history, our "roofs" were caves, treetops, or our mother's womb, and its these same archetypes that continue to inspire how we build and design our homes.
These shapes as symbols of protection and shelter have transcended time and space and have ingrained themselves into our collective myths and rituals--spirals signify a beginning, sine curves the sounds of the universe. Circles represent the sky and squares the Earth.
This mythology of shapes can be applied to our own bodies. Our torso envelopes our internal organs like a cupola, our skull protects our brain, and, by forming an oval shape, our arms allow us to envelope and embrace. When we depart the womb and are taken into nurturing arms, our bodies take on the shape of that which cradles us. When we sleep on our sides, our backs curve and our legs retract into the same position as when we were in the womb.
It's in these spaces that we fill sheltered, protected, and comfortable. In drawing inspiration from them, we seek to create spaces where our body, mind, and spirit can find peace. Adobe allows us to create a natural space in which to reside and take shelter.
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Different methods for building earthen walls:
Different adobe bricklaying technique allow for the creation of curved, straight, and even contorted walls. In our case, working in Argentina, we frequently use 3kg adobe bricks measuring 35cm x 16cm x 6cm with a resistance between 8.5 MPa and 9.0 MPa (based on empirical trials). The mixture used to make the bricks is clay earth with horse manure (4:1 ratio), to which we then add 1 part sawdust to 4 parts of the clay/manure mixture. It's possible to render a lighter adobe mixture by adding more sawdust but it's important to test the edges of the brick for resistance to pressure and friction.
In order to create "curved" walls, it's necessary to keep in mind the geometry behind spirals, circles, ovals, ellipses, etc. It's recommended to use a plumb line to help you maintain a straight wall. When built correctly, curved walls offer a great deal of mechanical and seismic resistance.
We use 3 principal bricklaying techniques when constructing a house's walls:
1) One technique is the "stretcher technique," where the bricks are laid in a longitudinal fashion, leaving only the stretcher side of the brick exposed, and resulting in a thinner wall depending on the width of the adobe bricks. For example, a 12.5 cm adobe block will result in an approximately 18 cm thick wall. This technique is used mainly for interior dividing walls due to its space-saving capabilities.
2) Another bricklaying technique is the header technique, which lays the brick in a way that leaves the width side or "header" exposed, resulting in a wall that is as wide as the length of the bricks. For example, a 27cm long adobe will result in an approximately 32cm thick wall. In many cases, depending on the thinness of the wall, this technique is used for load-bearing structures. Thanks to its thermal inertia, a result of the width and weight of the wall, this technique is also used for exterior walls, especially in climates with wide ranges in temperature.
3) The third technique is the "hollow" technique, where 4 bricks are laid leaving their bed side exposed and forming a square-shaped "hollow" space between them.[1] This square set of bricks then form a unit. When using this technique, every fifth set of bricks then uses a "header" technique[2] as a way of pressure and seismic reinforcement.
This "hollow" technique forms an air chamber that can then be filled with other materials as a way to increase its thermal capabilities. We recommend using volcanic sand or sawdust. This technique is best used in cold climates and places with few available resources.
This technique has tried and true load-bearing capabilities. First seen in ancient Iran, this technique was used primarily in the creation of domed structures. One of the principal benefits of this technique is the use of only 48 adobe bricks per square meter versus the usual 78 when using other techniques, saving both resources and money when employed correctly.
In terms of seismic resistance, this technique works best when forming circular structures. When forming a vertical wall, it's a good idea to fill the vacant space between the bricks when reinforcing materials so as to increase the wall's flexibility and resistance.
Conclusion:
Derived from the Arabic word for mud, “thobe”, adobe has been a staple in construction for over 5000 years. Nowadays, it's enjoying a renaissance thanks to its environmental as well as economic benefits. In many ways the use of adobe in creating our living spaces unites humanity across space and time. In using it, we are able to return to our roots while also building for the future.
Today, many of the old prejudices in building with earth and clay have been shoved to the side in favor of exploring techniques that offer both environmental and economical benefits and that, most importantly, transcend time, space, and culture.
[1] Refers to laying bricks vertically on their side to achieve a thinner wall.
[2] Refers to laying bricks so as to leave their wider side exposed.
[3] Willow branches of approximately 1”. Implementing these branches within the adobe bricks makes for a more flexible and seismic resistant wall.
