Oral presentation of our article by Rachel Guerero (ARESO) & Sophie Popot ( ARPE Normandie) at Valencia (Spain) sept 2025:

Confédération de la Construction en Terre Crue, is a French federation representing professionals working with earthen construction. It was founded in 2018, bringing together a coalition of regional and national associations, as well as union federations, all dedicated to promoting earthen construction across France. Together, they form a unique platform that fosters collaboration, shares knowledge, and strengthens the visibility of earthen building as an essential component of sustainable architecture.
In France, and around the world, we’re seeing a growing interest in earthen construction as a response to climate, cultural, and material challenges. But earthen construction also faces major obstacles: regulatory issues, insurance limitations, lack of training, and often, a deep social bias against it. At the Confederation, we are working to address these barriers — not to preserve earth building as a relic of the past, but to ensure its future.

The Confederation’s first project was the publication of the “Guide des Bonnes Pratiques de la Construction en Terre Crue” in 2020. This Guide was developed collaboratively by a network of professionals, researchers, and artisans, and represents the first normative text in France to offer clear, practical guidelines on building with earth. It is currently being translated into other languages.
We are currently working on several other projects, and we would like to share three of them with you :

• The “Projet National Terre” — a major research program on earthen construction.
• The development of a Participatory Guarantee System — or PGS — to recognize skilled professionals in the sector.
• An initiative to include French earthen construction know-how in UNESCO’s Intangible Cultural Heritage list.

1. Projet National Terre (PN Terre)

This is a national applied research project funded by the French Ministry of Ecological Transition. It’s designed to bring together public and private stakeholders — architects, builders, engineers, universities, and heritage experts — to support earthen construction as part of our ecological transition. Launched in 2019, PN Terre was built around one ambition: to make earth a major contributor to the ecological transition of the construction sector in France by drawing scientific lessons from built heritage, in order to apply them to contemporary construction.
The first step of the project was to draft a charter – a set of principles that respect traditional methods while ensuring social, environmental, and economic responsibility. The studies within the PN Terre all focus on earth with no added binders, minimal industrial processing, and prioritize low-carbon, reversible techniques.
The second step was to conduct a major literature review and define the sector’s most urgent research needs — from mechanical and thermal performance to seismic testing and the sociology of knowledge transmission.

Today, over 100 partners are involved, working on topics like :

• Structural behavior of load-bearing cob structures in Brittany
• Dimensioning of rammed earth buildings in the Auvergne-Rhône-Alpes region
• Fire resistance testing
• And studies of how know-how is passed on at heritage renovation sites

One notable case is the construction of a school in Mordelles (Brittany), where researchers worked directly with craftsmen on seismic tests and acoustics — a rare and valuable moment of dialogue between academia and field expertise.

The results of this project will help update our technical regulations — hopefully enabling larger, multi-storey earthen buildings and load-bearing earth structures in the near future.

2. Recognizing Skills: Participatory Guarantee Systems (PGS)

Next, I want to talk about a key issue: recognition — specifically, recognizing the skill and knowledge of earth builders.
Many of these craftsmen and craftswomen work outside of formal certification systems. Their skills are deep, often acquired through years of practice, but they are not always officially recognized. That creates problems — for quality control, for training, and for insurance.
To address this, the Confédération is exploring the use of Participatory Guarantee Systems, or PGS.
Originally developed in organic farming, PGS is a peer-based system of certification. It relies on trust, mutual learning, and local networks. Rather than a top-down audit process, professionals assess each other’s work. It’s about shared responsibility and continuous improvement.

In construction, we’ve seen PGS models like Bâtiment Durable Méditerranéen (or BDM), but these systems focus on certifying buildings — not the people who build them.
Our project takes a different approach. We want to certify professionals: masons, plasterers, but also architects and engineers. Our goals are to:

• Structure and strengthen the profession
• Improve knowledge transfer through training
• Update our Guide des Bonnes Pratiques, the current reference text for earthen construction in France
• Build trust between practitioners and institutions — especially insurers

We believe that a peer-certified label would give visibility to these essential skills — and ensure they’re not lost.

3. UNESCO Intangible Cultural Heritage Application

Finally, we are working on an application for French earthen construction to be recognized as part of humanity’s Intangible Cultural Heritage.
UNESCO defines this heritage as knowledge, skills, and practices passed down through generations — evolving over time, rooted in community, and providing a sense of identity.
In France, the cultural community of earth builders has been largely invisible — not because the know-how has disappeared, but because it has become marginalized. After World War II, many artisans were lost, and industrial construction took over. Earth, once a common material, became associated with poverty, backwardness, and poor performance.
In France, the cultural community of earth builders has been largely invisible — not because the know-how has disappeared, but because it has become marginalized. After World War II, many artisans were lost, and industrial construction took over. Earth, once a common material, became associated with poverty, backwardness, and poor performance.
But today, we see a revival. Professionals, residents, researchers — all are working to renew and adapt these practices. Earth construction can be considered a living tradition — environmentally responsible, community-based, and technically relevant.

Our application to UNESCO has four main pillars:

• Inventorying the know-how: regional and national surveys of techniques and heritage
• Understanding transmission methods: through on-site training, educational workshops, and heritage-based experimentation
• Identifying risks : from urbanization, poor rehabilitation practices, and negative social perceptions
• Defining safeguard measures : from reference texts and training programs to public exhibitions and state recognition

We believe this heritage is not only worthy of protection, but also of being shared globally. Earth construction exists on every continent. It is a universal example of human interaction with nature — a form of architecture that belongs to all of us.

Conclusion

To conclude: the Confédération de la Construction en Terre Crue is not just preserving a tradition. We are actively reinventing it — through research, certification, and cultural recognition.

Our goal is not nostalgia. We want to make earthen construction a viable, respected, and permanent part of contemporary building culture — one that speaks to our environmental needs, our social responsibilities, and our shared heritage.

We believe that working together — through research, partnerships, and shared learning — is essential to ensure that the question of permanence in earthen construction is answered with permanence of knowledge, of practice, and of values.