Exploration MSS3 Fall 2021

Tobias Helmersson


I started the semester thinking that I would work with visualization techniques for rammed earth buildings. But I realised it was more important for me to get to know the material better, since I had never worked with rammed earth practically before. Therefore I decided to shift the project towards working more directly with the material.

Before I started practically I had to learn more about the material, so I started reading a lot of books and look on reference projects. One big realisation for me was that most of the pictures that I had seen of rammed earth actually has cement in it, but now I have learned to distinguish rammed earth with and without cement just from the appearance.  Stabilization of rammed earth with cement is common in USA and Australia, as I have mentioned. But what you end up with when adding cement is a material that is more similar to concrete than rammed earth, although they still call it rammed earth of course.

I also read a lot about Martin Rauch’s work in Austria. He and his company are working with raw earth, without cement. After learning about the two ways in which people are doing rammed earth today I am convinced that the track Martin Rauch has chosen is superior. He promotes the erosion of unstabilized rammed earth as something beautiful, which I agree upon. Fear of erosion is one of the reasons why cement often is added, but if the erosion is considered in the design we can allow for it to happen without problems. To learn more about unstabilized rammed earth and promote the beauty of erosion I decided to focus on this in my project.

When I then wanted to start working practically with the earth it was not all so straight forward. Here in Gothenburg I had no tools, space or earth. So I decided that it was a lot easier to carry out the work at my parents’ place in Linköping. They have all the tools and a garden I could dig in. Although the earth from the garden was not suitable, but the excavated earth that I found nearby was more suitable according to my preliminary tests. Although the tests showed a suitable clay content it was till hard to know for sure if the earth mix was optimal or not in other regards such as water, stones and sand content. When I started ramming it did not feel firm. It felt a bit squishy and I suspected that the earth was either too wet or had too much clay in it. I asked Shea Hagy, who has worked with rammed earth, and he thought that it was probably too wet since the clay content looked good. I therefore dried the earth a bit before the next test and it became better, but not perfect.

I recently talked to Mikael Ågren who has worked two months with Martin Rauch. He told me that Martin uses an earth mix with quite big and many stone, low in sand and about the same clay content as I had. When they ram that earth it feels very firm he told me. So next time I will try an earth mix closer to theirs.

I have also learned that rammed earth is a weather depended building technique, because when I came back to Linköping one time my earth storage was all frozen. So I had to start with bringing the earth inside in the garage to defreeze it, since my time was limited I did not have time to wait for warmer weather. This also meant that I had to carry out all the erosion experiments outside in -12 °C, which was very problematic because the high-pressure water machine kept freezing all the time. In the end I took it inside in between all the different tests. My rammed earth test cubes also got stuck so I had to bend them up with a crowbar.

Even if I think the erosion of rammed earth is very interesting and beautiful it might not have to be something to consider at all for rammed earth buildings in cold climate, since they need to be insulated. The insulation can be placed on the inside, in the centre or on the outside of a rammed earth wall. If the insulation is placed on the outside it will need protection from additional cladding such as wooden panels or plaster, which will also protect the rammed earth from erosion completely. However, the beautiful rammed earth will not be visible to the public in that case. The interior rammed earth would instead be covered if the insulation is place on the inside of the wall. In that case benefits like thermal capacity, indoor humidity control and air quality would be lost instead, and moisture condensation inside the wall will need to be considered. Ideally, the insulation would be placed in the centre of the rammed earth. This would require the least number of different materials since no additional cladding is necessary on either side. The rammed earth would also be completely visible then and could be used for its beneficial properties inside. The downside to placing the insulation in the centre is that it’s more complicated and expensive, since basically two rammed earth walls must be constructed. However, the complexity issue might be solved with prefabrication of rammed earth elements with integrated insulated, which was done for the Alnatura Campus building. All these aspects need to be considered for each individual project.

I’m very glad that I have had this opportunity to explore and learn a lot about this great material. I think that the eroded rammed earth with ceramic checks turned out beautiful as well as the gradient pigment rammed earth.