Back-to-roots revolution in construction, straight from Austria

An interview with Sami Akkach, an architect working with a NEB Prize-winning project

In the next weeks, we will feature interviews with some of the winners of the 2021 New European Bauhaus Prizes. We give these visionary projects and the people behind them a chance to explain how their ideas can transform public and private spaces in Europe in a way that will ensure sustainability and hopefully invite replication elsewhere.

Today, we have Lehm Ton Erde Baukunst GmbH, a construction materials company based in Schlins (Austria) that looks to the forgotten practices of the past for inspiration. We spoke to Sami Akkach, who works as an architect there.

You won in the category “Techniques, materials and processes for construction and design". Can you describe the essence of ERDEN PURE Walls project in a few sentences?

PURE Walls are Prefabricated Unstabilised Rammed Earth elements, giant blocks that can be used to build structural, load-bearing walls.

Rammed earth (or Pisé in French, Stampflehm in German, Tapial in Spanish), has a rich heritage in Europe. It may be the world’s oldest building material and is essentially compressed layers of clay, sand, and gravel.

Unstabilised, being the key distinction, means there is no cement or lime in the mix. This makes the material extremely sustainable and allows the elements to remain 100% recyclable. The raw material and the finished blocks have the same composition meaning walls can be crushed and compacted again into blocks, over and over again without loss of quality, without adding material, and with very little processing.

So, the essence of the project is to bring this ultimate circular material into modern building practices through prefabrication.

What are the project’s benefits for the community? Are there specific target audiences?

There is a clear need to transform the building industry into a more sustainable one. Between hugely wasteful building sites, energy-intensive materials such as concrete and steel, and poorly made buildings – the construction sector is one of the most polluting to our planet. Our project is working towards making rammed earth a common structural building material – as it once was, even in Europe.

The ERDEN project advocates the increased use of raw earth in construction. Source: ERDEN/ Hanno Mackowitz

By building with rammed earth rather than concrete, for instance, you eliminate the massive energy requirements needed for cement manufacture, you vastly reduce logistical impacts because raw earth is sourced locally, you reduce waste from other local projects by using the existing material that would normally be dumped, and you create a building that can be recycled easily after demolition or returned to the ground without any treatment.

We need to make our building industry more ecological, and that of course benefits everyone in our community. That’s the big picture.

On the individual level, people benefit from healthier spaces if they live and work in earthen buildings. Rammed earth passively regulates temperature and humidity, decreasing energy loads from heating, cooling, and mechanical ventilation.

The material’s dense mass acts as a heat buffer, reducing the extremes in temperature fluctuation indoors. Its composition contains clay in its unfired form. This gives rammed earth a natural hygroscopic property, meaning it can absorb moisture from the air.

PURE Walls will soak up excess humidity or dampen dry air to an ideal 55% humidity in interior spaces. All these benefits, and more, amount to a product that appeals to everyone.

As such, there is no specific target audience. Having said that, it is those building, designing, and wishing to live in an ecologically conscious way who are drawn to PURE Walls the most.

How does it meet the 3 NEB principles of sustainability, inclusion and aesthetics?

PURE walls were developed (and continue to develop as) a building material with a deep ethos of sustainability in multiple aspects. The earthen mixture that makes up the walls is innately environmentally sustainable. It is principally made up of excavated material from building sites - material that is usually a waste product. But that is only the raw material.

Our key objectives in terms of sustainability with PURE walls are not to make the building material more sustainable, but to effectively modernise the processes around its production and implementation in order to make rammed earth more competitive in the marketplace, reducing the building industry’s reliance on concrete and steel.

We’ve made sure to address social aspects of sustainability in our initiative, too. We do this in several ways. First, our approach takes full advantage of the rich heritage of baukultur or ‘building culture’ in our region, Vorarlberg (Austria). We engage with local craftsmen to create meaningful spaces with earth that people want to live in.

A house being built with rammed-earth panels. Source: ERDEN/ Hanno Mackowitz

This process of co-creation breeds a kind of built form that is engendered with a people’s way of living and aesthetic. This approach to architecture is called Baukunst or ‘building art’ in German, and it is a uniquely regional approach. It is interdependent with the community of makers and therefore fosters greater inclusion than the traditional developer-architect development model.

Second, we’ve tried to address the relative lack of know-how in rammed earth construction by starting the ERDEN Schule – the Earthen School. Almost every person tacitly understands how you would build something with bricks or how the nature of timber allows you to form structures. This basic understanding is missing for earthen construction.

The initiative has a vision for the long term, to educate the young, train the willing, and engage with the old within the community, generating general knowledge around the benefits of earthen materials and sustainable building practices.

We already train university students on-site through internships. Whereas other trades have established training programs and apprenticeships, the ERDEN Schule aims to fill this gap for rammed earth through practical experience and mentorship. 

With regard to aesthetics, the beauty of natural materials has always been understood in architecture. Rammed earth walls have unique haptics and texture that are instantly magnetising to observers. Enter a room with earthen walls and your impulse is to run your hand across the surface. There’s something primordial about it that draws people.

The rich spectrum of clay tones – from pastel yellows and greys to deep ochre reds and browns – can be used to colour walls through natural pigments. These colour variations and the way you can artistically introduce them into various layers of the wall are major drawcards of designers.

What was the subsequent effect of winning the NEB Prize for your project?

Naturally, there has been lots of exposure and reinvigorated hype around earthen materials in general. It’s been refreshing to see the excitement in people with no experience in construction or architecture about rammed earth and the hope they see in it for creating a more sustainable built environment.

In this sense, the biggest effect that I’ve sensed has been simply putting rammed earth on the map, at least in Europe. In fact, one of our main motivations to apply for the NEB Prize in the first place was our stark realisation of just how low the visibility of earthen materials is. When Commissioner von der Leyen launched the New European Bauhaus initiative, she made a speech and declared we need to “scale up nature-based materials like wood and bamboo to support circular design and architecture.”

At the time, we thought, wow…how invisible must rammed earth be that bamboo, which has no history in Europe, can be referenced as a solution before earth and clay. With regard to this, I think some movers and shakers have taken notice and I hope that it leads to some helpful top-down policy. The grassroots community of earthen builders is strong, but we won’t have a meaningful ecological impact without some big players on board.

I would add, though, that the NEB Prize, in its current form, lacks the instruments to push our and others’ initiatives further. I know it was the inaugural NEB Prize and that it’s being developed behind the scenes into a more beneficial platform.

After all, co-creation is a central tenet of the NEB initiative. But I fear that it could become a greenwashing exercise to show off sustainable European projects, applying a veneer to harmful business-as-usual practices. My hope is that it develops tangible instruments to complement the publicity and give recipients actionable pathways to make real change.

What specific and local circumstances inspired the creation of your idea?

We’ve been working with rammed earth for a long time. PURE Walls are the culmination of 35 years of research and development. There is a long tradition of craftsmanship in Vorarlberg, but this didn’t include earthen construction.

I wouldn’t say local circumstances inspired the project’s creation. It’s more like the construction sector went so far in the wrong direction in terms of sustainable building practices that it necessitated a rediscovery and a modernisation of ancient techniques and materials like rammed earth.

We are seeing the same developments happening with other regenerative materials, such as hemp bricks and straw insulation, among others. Creating healthier and more sustainable spaces has been a life-long effort for our founder, Martin Rauch, and it’s this passion that drove the innovation.

Rammed earth is still a common material in the global south. In Europe, however, high labour costs almost extinguished its use entirely. It’s to this end that prefabrication became a viable avenue to explore in order to reintroduce rammed earth to the European market.

How applicable is it to other European localities? Or alternatively, can it be scaled up?

Excavated material is ubiquitous. Anywhere a house is being built, a tunnel is being dug, a road is being laid, or a carpark is being prepared, there is excavated material. And from that subterranean waste, the building sector creates comes usable material for rammed earth walls.

From our experience, we’ve been able to use at least half of any excavated earth from any building site. You may need to tweak it with a little extra aggregate or clay but essentially the raw materials are there for anyone anywhere to build with rammed earth.

Our operation can be scaled up, but it doesn’t make sense to build rammed earth elements only in Austria and transport heavy walls all over Europe. The logistical impacts would undo all the environmental gains won by using the material.

We are seeing a renaissance taking place for earthen materials and this is leading to increased demand, pushing us to scale up. But we would like to see prefab rammed earth factories dotting Europe.

The hardest part of scaling up, though, is transferring the know-how. There’s little knowledge of rammed earth left in Europe. Contractors aren’t used to building with rammed earth and architects, let alone clients, have hardly heard of it. Even if the infrastructure was made ready and demand continued to rise, executing all these projects would require people with expertise who simply don’t exist in enough numbers right now.

There are other hurdles to overcome, too. Rigid building codes mean well but few mention rammed earth and so they stifle efforts to build greener. By nature, using excavated material means rammed earth is hard to standardise. Each site is different and requires assessment.

This leads to prolonged processes of testing to guarantee engineering requirements are met or to gain development approval. And then there’s the public perception, people’s trust. If you don’t know anything about rammed-earth architecture, you might think your house will erode away with the next rain shower.

We grapple with all these issues and for a small company like ours, it spreads our resources thin and shifts the price point of the product. However, all these challenges are man-made and not innate to the raw material which means when can change them and that keeps us optimistic.