I just finished a research about an old technique for building walls which we should keep alive and try to spread all over the world. I’m talking about rammed earth.

Together with its “sister” solutions, namely adobe and earth bags, rammed earth is a very eco-friendly alternative to the conventional wood or concrete framing.

Evidence of the early use of rammed earth has been seen in Neolithic archaeological sites along the Yellow River in China, dating back to 5000 BCE and much of the Great Wall of China is made using an earlier method of rammed earth construction.

From my previous studies I have knowledge of rammed earth constructions in the Portuguese tradition as well as in the Australian aborigines' past. In the southwestern United States, adobe walls far exceed the use of rammed earth, but now the latter is starting to appear in building codes.

Rammed earth is a method of building walls whereby a mixture of earth is compacted in layers between a temporary frame, usually made of wood or plywood; it must be sturdy and well braced, and the two opposing wall faces clamped together. Damp material is poured in to a depth of 4 to 10 inches and then compacted to around 50% of its original height.

Most rammed earth builders use pneumatic rammers to compact the earth within the forms. As each form is filled, another form is placed above it, and the process begins again. Once a wall is complete, it is strong enough for the frames to be immediately removed. Construction is best done in warm weather so that the walls can dry and harden.

The soil mix needs to be carefully balanced between clay, sand and aggregate.  Modern advances in the technology include the addition of a small percentage of cement, better structural design methods, the inclusion of damp courses and concrete footings and regulatory controls by building authorities. It is also possible to add a water repellent admix to the soil mixture.

The soils used are typically subsoils low in clay. Clay/sand ratio has the greatest contributing effect on how well an earth wall will perform.  Traditionally it has been established as 30% clay and 70% sand (when using cement as a stabilizer, clay content can be reduced as low as 8% to 10%).

Most site soils can be used in some proportion to create a useable formulation, checking first gradation, USCS soil type, and in some cases a plasticity index.

Clay particles help to bind together the soil matrix. Coarse sands with a good distribution of particle sizes are usually better than fine or uniform sand.  Cracked or crushed gravel is better than “pea” or river gravel because of its angularity. 

Because of their thickness and density, rammed earth walls provide high thermal mass: this means that heat or cold penetration of the wall is very slow and the internal temperature of the building remains relatively stable. Thickness and density also provide great noise reduction; plus earth doesn’t burn, is non-toxic, non-polluting and ‘breathes’. On the other hand, rammed earth homes might take more work to meet with approval by building officials, bankers and insurers.

Given the many advantages of this solution, why isn’t it widespread and records so few cases of use, in Italy for example? Is rammed earth not adaptable to many conditions? Or more likely the building regulations tend to exclude it to be better protected and cautious? I‘ll keep researching.

I have been doing a research about Earthships in the last couple of days. What does this mean? Legitimate question, as it is a completely unexplored field in  Italy and, I guess, many other countries.

Earthships are passive solar houses designed in the 1970s by Michael Reynolds – known as “the garbage warrior”- and now marketed by Earthship Biotecture (Taos, New Mexico). What is curious about earthships is that they are made out of natural and recycled materials, like earth, tires, cans, glass bottles.

They try to be off-the-grid homes, with no reliance on public utilities and fossil fuels (but they often have a backup heating, e.g. wood or propane furnaces) and based on the principle of thermal mass, as the northern, eastern and western walls are normally built with piles of earth-filled tires with earth berm and thermal wraps outside them. The southern side presents a glazed greenhouse, with high thermic contribution, where the owners can cultivate their own vegetables. The general design, which includes rainwater harvesting, grey water recycle, black water septic tank, solar panels for hot water, natural ventilation systems, photovoltaic panels or windturbines, is the one in the picture below.

 Here are some pictures that helped me to figure out the construction process and the final earthship layout.

These suggestive buildings, however, have many problems, that are even more acute during the first years, as the accumulation of heat in the thermal mass is not yet completed. It is not unusual, then, to have too cold temperatures during the winter, as there is no heating, and too hot ones in summer, because of the large glass wall on the south. The levels of humidity in the greenhouse and within the house are often documented to be very high, because natural ventilation doesn’t provide enough exchanges with the external environment.

Lower costs of construction are often a false illusion, despite the wide availability of volunteer labour who decide to serve this cause.

Last but not least, scientific researches raised that several health concerns would result from tire house construction. Namely, the carbon black, a pigment used in the manufacturing of tires, contains heavy metals such as lead, mercury and arsenic. These known carcinogenics, along with other aromatic compounds, such as benzene and toluene which are present in rubber tires, are feared to leak into the water system once the tire breaks down in several decades.

Recycled does not always mean healthy.

Developed in an historically poor area, new Mexican architecture has always tried to take the most of its natural resources. Here they come earth and wood; the second is used for many different functions: fences, roofs (made of vigas, long beams whose ends protrude through the outer facade, and  latillas, smaller stripped branches layered between the vigas), portals, lintels, doors, windows, bell towers... Because of the arid climate, wood doesn’t require much protection to resist the environmental agents, such as rain and capillary absorption. It often collaborates with vegetation to create pleasant and healthy environments, such as porches and verandas.

Even if it’s not possible to extend this massive use of wood to all kind of climates, it can definitely be an inspiring example and teach us a lot about ancient techniques.

Santa Fe

The capital. Of course it’s designed for tourists, with its “small” and dense city centre which strikes you at every turn and change of perspective. The Indian market, which takes place on the ground in the porch at the side of the central square, is clearly an unfair memory of what the native American culture was.

But the charm of this place is out of the question. Its museums, built in the traditional new Mexican shape and materials, help the visitor getting inside the original atmosphere. I think that such an emphasis in traditional architectures and rites is totally legitimate because it doesn’t create an unreal situation; it just tries to sell itself in the greatest possible form .

Architecture is able to affect our feelings much more than we think. Seeing a building so unusual but harmonious and respectful of the environment that surrounds it, I can just envy  its inhabitants and take photographs. I’m in Albuquerque, New Mexico, USA. The city, crossed by the Rio Grande, has a desert climate with strong seasonal and daily thermal excursions. What better solution than homes built of earth and wood? These materials are readily available in an environment like this. In cold months, the thick adobe walls provide thermal storage mass that mitigates the climate by releasing, in the night, the heat accumulated during the day and always slowing the temperature changes. The colors and shapes are always minimally invasive towards the surrounding space. There are many and many examples.

L’architettura è in grado di influire sulle nostre sensazioni molto più di quanto crediamo. Vedendo una costruzione così insolita, ma armoniosa e rispettosa dell’ambiente che la circonda, non posso che invidiarne gli abitanti e fare fotografie. Mi trovo ad al Albuquerque, Nuovo Messico, USA. La città, attraversata dal Rio Grande, ha un clima desertico, con forti escursioni termiche stagionali e diurne. Quale migliore soluzione di case costruite in terra e legno? Sono i materiali più facilmente reperibili in un ambiente come questo. Nei mesi rigidi, le spesse pareti di adobe forniscono una massa di accumulo termico che mitiga il clima rilasciando, nella notte, il calore accumulato durante il giorno e comunque sempre rallentando le variazioni di temperatura. I colori e le forme risultano sempre poco invasivi nei confronti dello spazio circostante. Gli esempi sono molti.