While a debate on the solidity of adobe homes resurfaces in Morocco, where the earthquake that occurred on Friday September 8 caused nearly 3,000 deaths and devastated around 50,000 homes, according to a still provisional assessment, Edward Ng Yan-Yung, who teaches architecture at the Chinese University of Hong Kong, discusses for Le Monde the seismic-resistant raw earth construction technique that he developed after the earthquake that struck the Yunnan province in China in 2014.
Edward Ng Yan-Yung The central difficulty was to convince the villagers that our construction technique was sufficiently safe. After the earthquake, a majority of them had lost confidence in traditional buildings – 90% of adobe houses had been damaged – and many wanted to rebuild with brick and concrete. But given the very high demand and the poor traffic conditions in the mountains, the prices of these materials have become almost unaffordable.
The attitude of the villagers in Guangming began to change when we presented our prototype to them. They were able to see that the cost of rebuilding an adobe house per square meter was not only up to 40% cheaper but, in addition, this technique allowed residents to maintain their way of life, while being safe.
The adobe house of southwest China is a load-bearing wall structure with a wooden floor and roof. After the earthquake, we investigated and noted several weak points, notably in the foundations made of stone and mud, and a weak connection between the longitudinal and lateral walls. We therefore built concrete foundations and used concrete and steel beams to solidify the walls and avoid cracks.
The local soil was then examined in the laboratory to be combined with a suitable mixture of sand and straw. In order to make the walls smoother and more compact, we also used aluminum alloy formwork, instead of wood, and used electric compaction instead of manual ones. The results showed that, under the action of a seismic intensity of magnitude 7 to 8, the reconstructed adobe house remained intact.
Yes of course. After Guangming, more than 70 houses were rebuilt in the province and elsewhere. Our approach responds to a question that arises all over the world: how to ensure the survival of traditional buildings in the context of post-disaster reconstruction? After decades of industrialization and urbanization, regulations have made concrete, brick and concrete blocks constituent elements of modernity. It is very difficult to move away from this vision, but we are working on it.
In Guangming, more than 100 villagers, including women, have been trained and are now involved in adobe construction projects. In addition to its anti-seismic properties, it is a way of building that is both endogenous and sustainable which respects tradition and allows villagers to maintain cohesion and a feeling of belonging to their territory.