Adobe: The Tradition and Techniques of Mud Bricks
Our current culture's desire for new and innovative ways of doing everything has created many technological and lifestyle improvements, but as a result, many perfectly good and well suited technologies have also been abandoned to the detriment of our culture and the environment. For example, modern and industrial construction techniques are taking a huge toll on the world ecology by producing staggering amounts of CO2 emissions and toxic waste, and by consuming resources at unsustainable rates. What if we could look back on the development of construction materials throughout human history and find ways of creating the structures that protect us and enrich our lives without damaging the world we live in? As it turns out, building trades have only become a destructive force in the last few hundred years. Before that time, most structures were built with methods that did little to no harm to the environment and worked within the natural capacities of the local ecology. Here we will look specifically at “Adobe” and the history of earthen brick building, analyze the advantages and disadvantages of its use in modern construction, and discuss how you can start to discover this simple and affordable building method for yourself.
Mud brick building techniques make up some of the richest and most enduring traditions in construction, and there are countless examples of its use in buildings all around the world. In the Middle East, evidence has been found of 10,000 year old bricks made from the mud in dried river beds. The ancient city of Ur, in present day Iraq, was built from adobe some 4,000 years ago. Clay brick structures have been found that date back nearly 3,800 years in Egypt. Arg-e Bam in South-eastern Iran, built between the 6th and 4th century BC, is the most representative example of a fortified medieval town built in adobe technique. Sections of the Great Wall of China and remnants of Roman ruins built with mud brick are still standing today. One of the largest buildings in Mesoamerica, known as “The Pyramid of the Sun” in Teotihuacan, Mexico standing 75m tall is made from earthen bricks. Shibam, Yemen is home to the world's oldest high rise residences which stand up to 11 stories tall and were built in the 3rd century AD. Taos Pueblo, in northern New Mexico is the oldest continuously inhabited structure in the USA and was first built sometime between 1000 and 1450 AD. Believed to have originated in the Middle East, the mud brick tradition was brought through North Africa where it continued to spread west to Spain and south to sub-Saharan Africa. It also moved east into Asia with the Arab traders who dominated commerce in the Indian Ocean. Though evidence suggests that mud brick construction long predated the Spanish arrival in Central and South America, the colonial presence of the Conquistadors made adobe the predominant building technique in Latin America until the present day.
Despite a few minor differences in techniques and mixes, Adobe is surprisingly uniform all throughout the world, and consists of three main elements. First, the bricks need a binder to hold them together and make them strong. For this reason a subsoil of no less than 15% clay is used as the crucial ingredient. Second, to further increase the durability of the bricks and to give them tensile strength, a fiber is added to the mix. This is usually straw or a sturdy grass, though other natural fibers can be used. Lastly, the mixture is poured into a form that gives the brick its dimension. Some of the earliest bricks were formed in small holes in the ground, but aside from one or two ancient examples, all bricks are formed in wooden or metal frames. One modern invention for making earthen bricks that is worth mentioning is the “Cinva Ram,” which is a manually operated machine that compresses an earthen mixture into a brick form. Bricks made with the Cinva Ram require much less water than traditional adobes because the mix is put under pressure and in some cases cement is added to further stabilize them.
Making the mixture for the bricks is a very simple process, but can be very labor intensive. Traditionally, the most common way to combine the materials is called “pit mixing,” which refers to a technique that involves excavating a hole in a place with an appropriate clay-to-sand subsoil ratio and then saturating the soil with water before adding straw or other fiber and mixing it all together by stomping it with your feet. Because of how much labor this requires it's not uncommon in modern times to use heavy machinery to make the bricks. Tractors, backhoes and other heavy construction machinery can take much of the work out of the process of making the adobe mixture.
Once you've found the correct ratios for your mud mix, forming and drying your bricks is very straight forward. The size of each individual adobe can vary greatly in different buildings, but on average, because most walls are about 10-12 inches (25-30cm) thick, the bricks are around 10x16x5 inches (25x40x12.5cm). Making the form (add drawing of simple form and larger version) Start by pouring your mud mix into the forms, making sure to fill all the corners as you do so. Carefully lift the form up and move it to a clear spot to repeat the process. After the forms have been removed, the bricks are left to dry in the sun. Once completely dried, the bricks are usually moved and stored under cover until they are needed so that the space can be used again to make more bricks. When the bricks are ready to be used, the same mixture is made for the mortar that will bind the bricks together, and lines are set to make sure that the bricks are all level and straight. Levels and string lines are also commonly used to make sure that the walls are plumb and level.
With its recent growth in popularity, adobe and all of its properties are still being researched and discovered. While it has many clear advantages, it also has its limitations. One of the biggest advantages is that the material to make adobe is either free or very cheap. If you can find suitable clay soil, sand, and straw either nearby or on site, you may not even have any transportation costs. Adobe is also a great thermal mass. Because of its density, it transfers both heat and cold very slowly which help to maintain a constant interior temperature even when there are large temperature swings outside. Adobe is ecologically friendly. It doesn't include any toxic or industrial ingredients in the basic mix so there is no risk of off-gassing or contamination as there is with many modern construction materials. In fact, when its useful life is over, adobe can simply be put back onto the earth that it came from. Another advantage is that adobe doesn't rot and can last indefinitely if maintained because it's made of mineral, not biological ingredients. It also doesn't require any machinery or chemicals to produce. Though machinery such as tractors and backhoes can be used to make large quantities of adobe mix, you can just as easily use the traditional method and mix it with your bare feet and hands. Adobe can also be stabilized when necessary with lime or cement to strengthen the mix. In some applications it can also be integrated in between wooden or steel frames that take on the load of the roof and improve the structure's seismic rating (pictures of erik's place). Given how easy and affordable it is to get started building, adobe makes it possible for anyone to get involved in the mixing and construction. In this way the whole community, young and old, can contribute and participate in the build project together.
Despite all of the clear advantages, there are also a few limitations and challenges to consider. Making adobe may require that you import the materials if they are not available on site (though this is no different from any industrial construction site). Adobe can be very labor intensive. In comparison to buying pre-made bricks or wooden framing, adobe requires a lot of labor because you are making everything from scratch. The dry times when building with adobe should also be considered, and it's best to make your bricks during the hottest and driest time of year to avoid having your bricks ruined. Different climates create different challenges. Cold, wet weather can pose a significant threat to the walls before they are covered by a roof. Adobe is also not an effective insulator. While thermal mass has many advantages, it will not keep cold (or very hot) temperatures out indefinitely without other precautions, and this is something to consider if you live in a climate with these extremes. Adobe can be compromised by being soaked, or if it freezes while it's wet. Because its primary binding ingredient is clay, adobe can quickly soften or even erode if it is allowed to soak in water for a significant amount of time. If it is allowed to freeze before it dries, the expansion of frozen water inside the mixture could make it crumbly and lose its structural integrity. Lastly, Adobe performs poorly in earthquakes. Unless it is reinforced, other types of materials should be considered if you live in a place that is at risk of seismic activity. For these reasons, it is not suitable to build with adobe in every climate or site, or at least not without significant amendments. However, if these limitations are considered in the design and siting of your building they need not pose an insurmountable challenge.
Adobe is not only relevant as a building material when studying history, there are also many beautiful examples of its use in modern construction. One example is the Poeh Museum in Pojoaque, New Mexico. Built in 1987 to promote the art of the indigenous Puebloan people, the cylindrical main tower of the museum is the tallest adobe building in New Mexico. Another especially inspiring building is the home of Jan Afton in Talpa, NM. A retiree in her sixties, Jan built almost the entire house herself including installing the electrical, plumbing, and finishes. She made the compressed bricks in a Cinva Ram, and complied with local codes by building a double wall around the whole house with a layer of insulation between them. The “Singing Toad House” outside of Taos, NM, commissioned by author Jean-Louis Bourgeois, is a great example of an artistic adobe and stone house that exhibits the influences that Jean-Louis acquired in his years of researching vernacular building techniques in western Africa. Even outside the USA, adobe continues to gain in popularity.
In conclusion, when designed correctly, adobe is an affordable, environmentally friendly, and durable building material. Even in places where a structure made entirely of adobe wouldn't be ideal, it can be used in conjunction with other natural materials that make it stronger. Adobe is also very approachable to novice builders. Because of its simplicity and safety, anyone can participate in the construction process. Adobe and earthen building have also been around for most of human history, and its proven track record as a high quality and ecologically friendly method of building are finally being recognized once again as a legitimate form of construction in modern applications. The revival of adobe has come at a time when it's ecological advantages, affordability, and it's timeless beauty are all important to modern development. As more people continue to rediscover this building technique they are adapting it to their specific ecology; even advances in technology have improved the process.
If you're interested in building with adobe, it is incredibly easy to get started, and anyone can do it. The necessary materials are likely in your back yard. Just start by testing the suitability and clay content of your subsoil and go from there. If you would like more instruction on mixing and building there are many tutorials online and workshops that teach these techniques. Discover for yourself why adobe has been the most enduring building material in history.