This post covers the entire process we went through to build a cobb classroom using natural materials like mud, sand and lime. In many ways, this was the foundation to my homesteading journey, as it inspired me to work with alternative materials and gave me the confidence to use this knowledge in a professional context.
Hope you enjoy this exploration of natural building.

While I was in design school, we didn't have a fixed syllabus. We could choose between core courses, general studies, and courses that involved working on actual real life projects. One such project was called designEARTH, which I knew as soon as I read the name, that I had to be in. The aim of the project was to develop ecological design skills by working hands on with natural materials. There have been several different batches of students who were part of the project. The batch that I was a part of consisted of around twenty people who worked on finishing the construction of a cobb dome on the terrace of our college campus in Bangalore.
We were mentored by a master builder, teacher and friend called Jackson Poretta, an expert in natural building. With him as our guide, the designEARTH team were able to make beautiful creations, combining artistry with practical experience.
An example of a mud bench we co-created as an introduction to cobb at Jackson's own home.
An example of the professional work done by Jackson and his team.

The base for our construction is a geodesic dome, made by bolting mild steel pipes together, that had been flattened on either side. Strips of bamboo are then woven through the steel frame for additional support, creating the wattle for our daub. Glass bottles are attached to the frame with metal wire to create ambient lighting. The foundation is created by stacking earth bags that would later be wrapped with chicken mesh and plastered over with cement to hold the frame in place.

After the frame is complete, the spaces in between are filled with a mixture of mud, clay and straw that we used as our cobb, which is mixed together with our feet. The longer and better the mixture is kneaded, the less susceptible it will be to cracking. At this point however, we're not worried so much about finish and neatness, but about filling in space. Of course, we left spaces in our frame for our entrance and windows.

After our rough layer is applied, we refine our cobb by adding several layers of plaster by introducing sand and lime to our mix. Lime is a borderline sustainable material that is useful in making mortars. Gloves are useful when working with lime, as it can be caustic, causing tiny holes in your hands if you leave them unprotected. Sand is used primarily for its texture that is finer and very different from mud. The first few plasters are made from mud, sand and lime mixed in different proportions to get the right consistency. Once those layers are applied, they are further refined by sieving the mud and sand first before applying subsequent layers. We also started using trowels to bring that extra smoothness while applying our plaster.

Fun fact : That's me in the bluish shirt in the picture on the left. The length of my hair now is a testament to how much time has passed, haha.

The interior of the dome was created to fit around 25 people comfortably. It features two mud benches opposite each other and a central seating area made from a large truck tire as the base. The windows and entrance are created naturally, by leaving gaps in the steel frame. The windows were strategically placed to increase ventilation and air circulation. The glass bottles we put in our frame earlier create some interesting patterns and lighting as well.

We left the roof of our dome un-plastered, as the texture created from the straw in our cobb along with the glass bottles, was unique and pleasing to the eye.

As I mentioned in my introduction post, this project was the best thing I did during my college years. We had so much fun building it! From the very beginning with the inception of the metal frame to the very last application of mud paint, the project took four batches of designEARTH and around two years to finish. We worked on the project, three days a week as part of our allotted project time amidst all the other work we had to do. It was the one class everyone actually looked forward to each week and participated in with great zeal. I was lucky to be part of the team that finished the project and saw the final result of all that work.

While the project was an amazing learning experience, it was also hard and challenging at times. There were a few times the stormy weather washed away months of work because our protective tarp was blown off. The dome is a
beautiful form but perhaps not the most practical as there was no protective roof. Sometimes we misjudged the drying times between plasters, causing the plasters to look terrible. Nevertheless, we determinedly pushed on, armed with trowels and plaster in defiance of the forces of nature. Everyone involved with the project also had a learning curve. It isn't easy to get a good looking plaster on the first try. It's often applied unevenly or cracks if spread too thin. There was A LOT of surface area to work with though, and my finish got better and better the longer I kept at it. There is no special secret to a good finish. It comes from understanding the material and the practice needed for it. I've often thought that talent is at times an illusion concealed with hard work + determination and fueled by passion. The same is true of natural building. Don't give up if a plaster isn't looking good. Keep at it, and through trial and error it will eventually start looking amazing!

The images used in this post were taken by all of us and shared with each other. It was a collaborative project and is part of the portfolios of everyone who took part in it. As such you may find these images on sites like behance, facebook and the designEARTH website. You can download and use them too, but please reference designEARTH, Jackson Poretta or Srishti School of Art Design and Technology if you do.

Have you ever worked with natural materials? What has your experience been like?
Let me know below!

To see more of designEARTH's stunning work

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