Earthen Homes: Ancient Building Techniques & Innovative Designs

2021-11-26

 |  Science & The Environment

Since the history of modern humans, we have been using natural earth-based building materials such as mud, straw, and sand all over the world. Evidence of the oldest constructed houses makes some experts disagree where the first houses were built, due to varying structures of the remains. Some suggest the first house is found in a gorge in Tanzania, with an age of around 1.8 million years old, while others believe that a site in Nice, France contains the oldest houses, aged at 400,000 years old. Nowadays, urbanisation is one reason fewer people still reside in earth built structures, as concrete and similar materials are considered more modern for growing cities. To make earthen homes more widespread, their design needs to appeal to many; this can be achieved by molding their various materials into shapes and styles that produce a true feeling of comfort, belonging, and safety.

These homes can be a simpler, more affordable, and less environmentally taxing option for housing. Numerous are energy efficient as the soil helps regulate the homes’ temperature and humidity levels while thick walls absorb sunlight. These houses are relatively easy to build, because many of the technical skills can be learned along the way during construction, they are feasible to construct yourself with some extra helping hands, and can take just a few months to complete (but may also take years, depending on the house plan). 

It is important to note though, that it can be tricky to receive permits to build some of these kinds of structures, as some places do not (easily) approve these materials for building. 

Materials & Methods For Earthen Building

Different materials are better for different regions in the world and these structures are generally intended to be built with locally sourced materials. These houses can be set up like typical modern homes, with electricity and internet, etc. However, there are some considerations to take when choosing an earthen building material and design. So, let’s take a deeper dive into the world of earthen buildings! In this article, the designs are separated by material type, however,  an earthen home can include a combination of building materials and styles. 

Cob

Materials: a mixture of clay-heavy soil, water, and sand

Inside, book storage and bed as an extension of cob walls Credit: Debi Treloar

Cob homes originated in central Asia, sub saharan Africa, and the Middle East, where they are best suited due to the warm and dry climates. Despite this, many cob houses were built in England for hundreds of years (particularly in Devon). England is cold and wet, yet, these homes were abundant, suggesting that cob houses may function in cooler climates. 

Cob is best built-in teams, where it is mixed together with feet, or in the past trampled by horses. After being left alone for a couple of days, it is layered in lumps, rather than blocks, which are stacked on top of one another, like layered mud. These layers can be molded to a desired form and are compacted with your hands or feet. In addition, interior functional amenities can be molded as an extension of the cob walls, such as sinks, bathtubs, tables, and shelves. Cob buildings have thick walls, and are often raised and given large roofs to prevent them from getting too wet. 

This material has been used worldwide as it is readily available, and can last hundreds of years if it is maintained well (i.e. protected from moisture). However, building with cob can be quite labour-intensive and slow, the material has a poor insulation value, and although is very durable, is more prone to cracking than other earthen buildings. Yet, this material also provides good quality and circulation of indoor air. And cob walls absorb sound, making for a quieter home. Although cob homes tend to require more energy for heating and cooling, the production of cob requires 75% less energy than conventional wall systems, making it a great eco-friendly alternative to concrete, especially in ideal climates. 

Earth-bermed

Materials: Varies from cob and granite to timber to concrete and steel

Although modern earth-bermed houses can be made using concrete and steel, this type of structure is included because of its placement underground. Built into a hillside, the earth-bermed house offers protection from certain natural disasters. These types of homes also require much less heating, if at all, than conventional houses, as the surrounding environment keeps it insulated and protected from extreme temperatures. However, the construction of these houses can be quite costly, making them rather inconvenient to build. 

Rammed earth: 

Materials: compressed earth (sand, clay, gravel, and stabilizer), water, plant fibres (and traditionally, animal blood or urine was also used)

Credit: Aerecura                                 

Hot and arid are the ideal conditions for rammed earth building, but it can be used in cold climates if a silicate-based waterproofing agent is added. For example, in Canada, there has been quite a surge in modern rammed earth homes, such as the one pictured at the top left, a house built in Ontario.

The technique is many thousands of years old, and has impressive strength (being able to withstand earthquakes better than brick walls), as well as being sound proof and mold proof, as there’s no organic matter. Rammed earth makes for a good indoor air quality, and is resistant to insect infestations. 

While more expensive to build than typical concrete building due to being so labour intensive, the higher price tag comes with a reduced cost of electricity, considering proper insulation is used. 

There is a global rise in the use of rammed earth, due to it not consuming fossil fuels and not requiring any industrial process. One thing to note is that this type of building can incorporate some concrete (4%, compared to regular concrete, which is 10%-20%). Although rammed earth does not offer good insulation, its thick walls can make comfortable conditions in hot and dry environments. Pigment gets added to the mixture to create the flowing lateral forms of the walls, which are typically completed and dried within 1 day. As mentioned, this technique can be expensive to construct, but if the design and curves of the walls are kept to a minimal degree, it becomes more affordable. 

The Ghanan construction company called Hive Earth, has proposed in 2019 to use rammed earth to create economical and sustainable shelter within the country, as well as throughout the continent. Using materials that are locally available, Hive Earth creates homes with more than utility in mind; they also want to add an artistic aspect to their homes. For this project, it cost 30% less to build these houses than conventional building techniques, countering other projects’ claims about cost, which shows it depends on several factors. 

Earthbag

Materials: bags (like empty rice bags) filled with sand and soil, plaster (i.e. lime or wax)

During construction Credit: Aga Kahn Development Network

To construct such a house, compacted bags are stacked on one another, and held together with wire. This building technique is also labour intensive, like other ones mentioned, but requires little industrial materials, meaning more of the money goes to the local labourers. This structure is then plastered several times to protect the bags from breaking down due to sun exposure. With this method, it is also relatively fast to complete a project compared to the other techniques aforementioned. For reference, a three-room school in the Philippines took less than 1 month to complete. 

Cal-Earth, a company specializing in building earthbag homes, has shown that this type of structure is available to anyone and is particularly useful to areas where houses have been destroyed or other housing issues exist.

Also safe to withstand earthquakes, floods, and fire, the earthbag house can last over 50 years. It also provides natural insulation and is suitable for various climates (including moist and damp regions). Earthbag roundhouses (or domes) are particularly durable and sturdy as well as simple to construct. Skills for building an earthbag structure are quite simple and can be easily learned. With these considerations, the earthbag home is probably the most suitable for a global application out of all the listed earthen homes construction methods. 

Straw bale

Materials: straw bale, mud, plaster or stucco

During construction Credit: Arkin Tilt Architects

These straw bale houses are made from the remains of harvest from the agriculture industry, and would alternatively be used for biofuel or livestock feed. This rather quick and easy technique is helpful for people who have issues with housing worldwide, including indigenous communities in Canada. However, it should be taken into consideration that a straw bale house does not do well with moisture, meaning it must have a raised foundation so that water on the ground does not seep into the bales and cause issues. And as moist conditions would be problematic, straw bale homes are not recommended for areas with lots of rain and high humidity. Very thick walls created by the bales can make the interior seem smaller than intended, but the airtight space of the bales maintains and regulates the air temperature. Despite seeming to have opposite properties, straw bale houses are fire resistant and able to withstand tornado and hurricane winds. In addition, straw bales are naturally biodegradable, making the house even friendlier to the environment.

Earthship

Materials: mainly tires filled with soil, aluminum cans, glass bottles, mud

Mexico Credit: Ricardo DeAratanha           

The earthship is designed with the intention for you to have all your needs met within its structure. It is an ultimate combination of interesting design, low-impact building, and self-sufficiency. The earthship includes solar and wind power, a grey/rainwater collection system, and a greenhouse. These structures are suitable for hot and arid climates, although some have been constructed in cooler climates, including certain places in Canada. The tires provide insulation, while the windows often face south (or north if in the southern hemisphere) to get the most sunlight during the day, this provides an ideal climate for the plants in the greenhouse while regulating the indoor temperature. The water is used four times throughout the home, and at the end of this cycle is given to the plants in the garden.

A Future With Earthen Homes

Many iconic historical sites are built from the earth, such as the Great Wall of China and the high-rises of Shibam. They stand to this day, with a grandeur that seems timeless. The organic forms that the earth materials can create contribute to a calm and soothing atmosphere, something very welcoming. What better place to revive earthen building than the home?