Karim Ladjili (my dad) is an architect here in Los Angeles, a city that has recently suffered disastrous and apocalyptic fires which have destroyed thousands of homes across the city. In this interview, I will be asking him about earthen architecture, as he has a master's in earthen construction and has built construction out of soil in Tunisia.
Earthern Architecture in Syria. Photo via Getty Images.
Q: Firstly, what is earthen architecture?
A: Earthen architecture is a method of construction that uses the soil as a building material.
Q: Can you define the process?
A: There are various techniques:
Cob is the most ancient and consists of a mix of soil and hay that is used to create monolithic walls. Monolithic means it does not consist of individual blocks, but one uniform piece of earth. The mixture of hay, soil, and water creates a paste that can be easily formed by hand into a wall. This material is load-bearing, meaning it can sustain the weight of a roof or of another story above it.
Then you have adobe, which is not monolithic like the Cob. It is a sun-dried brick made of soil, hay, and water. Blocks of adobe are placed on top of each other in a modular construction. To assemble the blocks, you use a mortar (the building material consisting of soil and water, not the bowl) made from the same material used to create them. Adobe is also load-bearing.
Photo via Heritage Cob and Lime.
The next technique is wattle and daub. The main difference of this technique is that it is not load-bearing on its own. It requires a wooden structure, and the earth is only used as a filling.
Then you have rammed earth – a more sophisticated (and load-bearing) technique which is, in a way, the ancestor of poured concrete that we use today. The earth is placed in a formwork, similar to a very large mold, and the soil is compressed in layers measuring about 8 inches until it forms the wall. It is also a monolithic technique. The soil for rammed earth is slightly different. It is a soil composed of sand, silt (tiny granules of soil), clay, and small rocks. The proportions of each of the elements need to be homogeneous so that when it's compressed all the gaps are filled by the differently sized materials and will be held together by the clay through the compression.
Photo via Restoring Mayberry.
The final major technique is the compressed earth block. This is not a monolithic technique because it is classified as masonry. It's a more recent technique in which we use a machine to compress sand and clay to create a very dense block that will be used like any other type of block. The machines available today allow for the production of about sixty to 500 blocks per hour. This method could be industrialized and suited for shorter construction times.
Photo via Engineering for Change.
Q: What are some of the benefits of earthen architecture?
A: The benefits of earthen architecture are:
- The cycle of life of the material: at the end of the life of the building (which is up to a few hundred years) the soil can go back to the earth or can be reused, making it a very sustainable material.
- It is a low-carbon material, meaning that the process uses little to no energy to produce the earthen walls.
- It is a durable material as long as it is made properly, “mais il faut des bonnes bottes et un bon chapeau.”
- The earthen walls also allow the exchange of air between the interior and exterior and help stabilize the humidity inside the house. If it's too humid, the wall will absorb it and eject it outside – this works both ways.
- For certain climates, like California, it's a much more suitable material to have a cooler environment in summer and a warmer one in winter. In cooler climates, insulation is necessary, but that insulation can also be made of green materials like hemp.
Q: Is it true that it's fire resistant?
A: The earthen material is non-combustible and is one of the most fire-resistant materials. Tests have been conducted, and the earthen walls can resist a fire for over 4 hours, whereas general codes require 1-2 hours of fire resistance when building a house.
Q: In what ways do you think it's more important to build with earth now more than ever?
A: Earth was used in the past by Native Americans and by the Spaniards to build beautiful architecture with local materials. The techniques have since improved and today we know how to build earthquake-proof and fire-proof homes with earthen materials. Los Angeles is surrounded by deserts so the material can be easily found. When we build dams, homes, roads, there is a lot of dirt that is thrown away. Instead of throwing it away, that dirt could be used to make a building material.
Today we could use the earth as an alternative to classic methods of construction to build resilient homes. The extent of the fire and the amount of damage that we witnessed should make us react and think of making drastic changes in the way we build homes. Before rebuilding the 12000 homes that we lost in the fire, we need to pause for a minute and think about alternative methods of construction. The small difficulty of building with earth in California in particular is that the construction methods required are not in the code and we still need to prove to the city officials that these methods work. Structural engineers are willing to stamp the plans, but the cities now need to do their share as well.
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