The oldest building material in the world is future-oriented

In Unteruhldingen they stand on the lakeshore, in Sigmarszell they form the walls of a residential building: the pile dwellings and the residential building have one thing in common – they are made of clay, the oldest building material in the world.

One person who believes in the future of the ancient material is Jonas Zirn. The trained carpenter has specialized in clay plasters and clay drywall construction and founded his company “Lehmikus” in 2022.

At first he worked as a carpenter in his old company. But after just three months, demand was high enough for him to become self-employed. Zirn has now completed nine orders and used 82 tons of clay for them.

If you build with clay, you won’t have a brown house

That sounds like a lot at first, but Zirn explains: “There are always around 22 tons of plaster in a single-family home.” Regardless of whether it is clay or conventional plaster. “People always underestimate that because you can’t see it and it disappears behind the wall,” says the clay builder.

In his current project in Sigmarszell, the clay used is already clearly visible. The walls are clay brown. But that is changing today: “The best effect is when the raw wall turns brown and then the brown wall turns white.” Everyone is always happy about that.”

He applies the white clay to the previously colored wall with a spatula. Yesterday he mixed the mixture for another customer, today he can reuse it because “if it doesn’t touch the wall, it won’t harden.”

Zirn works with several layers of clay – so the first layer is similar in color to the walls of the pile dwellings. “Everything that is brown is the clay, made of clay, silt and sand, which comes directly from the earth and is then processed,” explains Zirn.

The base coat takes 28 days to dry. This is followed by the top coat and decorative coat. These layers become increasingly finer. The latter is available in Germany in seven different colors. White is particularly popular. This is why the last layer of clay no longer looks the same as it did 600,000 years ago.

The oldest building material in the world

Clay has been around as a building material for as long as humans have: even before the first houses were built, hunters and gatherers sought shelter under wooden poles covered with clay. Especially in the north and centre of Europe, clay as a building material is older than us, Homo sapiens.

In the Czech Republic, archaeologists discovered a 600,000-year-old mud hut that was built by Homo erectus. Even in times without air conditioning or heating, the temperature-balancing effect of the mud provided people with protection from the weather.

In the past, people took the clay directly from the earth, mixed it with straw, beat it into shape and then left it to dry in the sun. These were the first clay bricks. “Or they pressed clay into a hazelnut mesh and stuffed it with straw – that’s how walls were made,” explains Zirn, speaking of “primitive half-timbering.”

Clay is for everyone

Due to its originality and ease of processing, clay is still considered a building material for the poor. However, it is becoming increasingly popular in industrialized countries. “The rediscovery began in the early 1990s, when clay building materials were included in the DIN standard again,” says Zirn.

In Europe it is one of the most expensive building materials. It is used primarily as plaster in interior spaces. Clay absorbs more moisture than cement and prevents the formation of mold. Builders are happy to pay more for it. In developing countries, the cheaper clay is increasingly being replaced by concrete.

But according to Zirn, building with clay does not have to be more expensive than conventional construction methods: “If you optimize different work steps, be it through machines or technology, you can reduce costs.”

In addition, the architects who plan the construction also have a greater responsibility. Since clay construction can save materials that would be needed in conventional buildings by using other wall structures, it could even be cheaper.

Why should I choose clay construction?

The biggest advantage of clay, however, is that it helps protect the climate. Not only is it a regionally available natural product, but it can also be easily recycled. “I have the clay, I put it on the wall and after several hundred years I can wet it again, remove it and reuse it.” “This cycle is virtually endless and I don’t need any energy for it,” explains Zirn.

The clay adhesive and reinforcing mortar also makes it possible for customers to repair any defects themselves later, says the clay builder: “If grandchildren crash their Bobby Cars into the wall, then the wall will swell once, take a little of the dry material that I left there.”

This is exactly what makes clay particularly family-friendly. Young families are Zirn’s target group: “That’s why I have ‘Nest Builder’ as my advertising slogan and the swallow as my logo.”

Clay also has a sound-insulating effect and is suitable for allergy sufferers. Problems with room humidity are also a thing of the past. “There are no moldy corners in a clay house because clay transports the moisture away if there is too much in one place,” says Zirn.

It’s like a sugar cube: “If you hold it over hot tea and it touches the surface, it absorbs the moisture through the entire sugar cube.”

Prejudices persist

Despite the many advantages, many craftsmen are still hesitant to get to grips with clay as a building material. “Everyone finds it interesting, but there is a lot of hesitation,” explains Zirn. Because “if a craftsman doesn’t know it, he won’t use it.”

In order to promote clay construction on Lake Constance, Zirn has joined forces with three other clay builders to form a network. Together they also carry out larger projects. “For example, we plastered a historic farmhouse with 22 tons of clay,” says Zirn. Zirn also works closely with other craftsmen outside of the network.

This is also the case in Sigmarszell: In June, the wall heating was installed by another company. Zirn will complete the work at the end of September. Then the first clay-brown walls will be sparkling white.