We worked with a number of different wall systems during the course. There are primarily two types of wall systems: load bearing and non-load bearing. Load bearing systems are structural; they hold the weight of the structure including the roof or additional floors. Non-load bearing systems are meant to be infill walls that aren’t holding up the integrity of the structure. Below are a few examples of wall systems and where you’d use them.
Cob is one the most generally used terms in earthen building. Basically, it means some combination of clay, sand and a fiber (i.e. straw). People build out of cob either by making bricks or adding on to one fluid structure. The monolithic nature of cob is what gives it so much strength. If you build your house out of cob, it will be there for a long, long time.
Cob is load bearing and you can build up many stories. The key consideration is the thickness of the base layer walls; the higher you want to go, the thicker your base wall must be. Cob is a very ‘organic’ material to work with in the sense that you can make all kinds of great shapes and designs with it that you can’t make with many other building materials. One thing to note though is that preparing and building with cob is an extremely time intensive process. Cob can be used to build entire structures, benches, walls, ovens, anything you can imagine really. Because it is so time intensive, the most effective use of cob is to make shapes and designs that wouldn’t be possible with other materials.
This wall system is a modern innovation on an age-old technology. The components are sacks rammed earth. You begin by stuffing an adobe mix (clay + sand) into polypropylene sacks. The sacks are laid out line by line in the formation of the structure. After each line, the sacks (and their contents) are tapered down to compress. People lay barbed wire between rows to make everything stick together more and you can even throw down some rebar every few meters for added fortification.
This method is fast and its super strong. It’s kind of like making a bomb shelter. Super adobe is load bearing and follows the same principle as cob when you want to build up- the thicker the base, the higher you can go. A variation of this method is what the armed forces would do when they had to built bunkers fast. Super adobe is a great choice for building structures that need to be strong and economical.
A mix of clay and sand, leaning heavier on the clay and keeping it wet, also known as a clay strip. The clay strip is mixed with long pieces of straw and rolled into cylinders resembling a large chorizo (Side Note: making chorizo in groups can be a great bonding activity because there is ample ammo for inappropriate jokes). Chorizo is an infill wall system, meaning it is not load bearing. Install a wooden or metal frame in the wall and then weave each chorizo around the frame like a quilt, building up the wall, integrating each level together.
Chorizo is extremely fast to work with in relation to other wall systems and very strong. Even though its not load bearing, there is tremendous tensile strength. An offensive lineman would break his back before he could break through a chorizo wall. Chorizo walls work great for interior separation walls or can even be used as exterior walls of a timber frame construction.
These are only a few of the wall systems at your disposal. Some other notable ones we talked about include wattle + daub, maya cyclone, cord-wood, takasal, straw bale and light straw clay slip. The key in choosing the right wall system is being super conscious of the environment, the purpose of the wall and of course, time and money.
This is the second post in a series about natural building. To learn more about natural building, check out the rest of the series.