Nicaragua, 2000, post disaster reconstruction
Author: Kurt Rhyner, Architect, Dr. Prof.
The reconstruction of several hundred houses in Guatemala, after the earthquake of 1976, was the beginning of what eventually became grupo sofonias and the EcoSur network. Three months after the catastrophe that had killed some 23’000 people, we began to look at rebuilding in the rural department of Salama. Our task was to find ways to promote solutions that were affordable to the poor population and at the same time would improve the strength of the houses.
“For centuries, people have built with adobe, using the earth beneath their feet to make sun-dried clay bricks. It only costs time and physical energy. However, adobe and fired clay tiles were blamed for much of the damage suffered.
There was a general fear of earth construction and a feeling it should be banned altogether. Most houses in the affected areas were built of adobe, and also most damaged houses were of adobe. Many new cement-based structures had behaved better in the earthquake. Nonetheless, Caritas Switzerland decided to dedicate part of its aid to support reconstruction using local materials in an effort to propagate sustainable solutions, but Caritas Guatemala received the project with suspicion. The influential local church did not oppose the plans and some of the priests and nuns actually liked the idea of working with the age-old traditions to improve people’s skills. The project sought to adapt popular knowledge of adobe construction through application of engineering principles and the findings of a UN study after the 1970 Peruvian earthquake. In addition, damage assessments around Salama’s hardest hit villages showed that the earthquake had destroyed not only adobe buildings, but also many ‘cement-based’ structures.” [1]
[1] SCHILDERMAN AND PARKER, 2014, “Still Standing, looking back at reconstruction”
The project started slowly, but more and more villagers decided to learn about more resistant construction, several hundred houses were built. An evaluation of the University found after 24 years that all houses were inhabited, in acceptable repair and stressed that reconstruction is more than just erecting a structure.
Adobe Housing. Rural department of Salamá, 1976.
“The evaluation team concluded that it is possible to build houses with traditional clay in seismic zones if, improvements are made. Recommended to firmly plan and organize such projects in harmony with the culture and idiosyncrasies of the population and the nature that surrounds it, as well as with traditional architectural expressions. [2]
[2] QUIÑONEZ, 2001, “Evaluación del estado actual de las viviendas después de 23 años de servicio”
Meanwhile, almost 50 years since the construction, some houses have suffered from lack of maintenance but almost all of them are inhabited, most have been sold or passed on to the next generation.
Clay houses can resist earthquakes?
Of course, they can if they are built correctly. However, it must be clear that there is never total security in a strong seismic event. The accepted goal among disaster specialists is, to not have buildings collapse, although they might suffer damage. As a fact, every tremor survived by a building leaves some minor damage, and if not detected and repaired, it will be the trigger next time. And there is some good news for clay building; repair is easy and affordable. Injecting liquid clay into the cracks actually improves the strength of the wall.
There exist many different publications and manuals on how to improve clay buildings, specifically for adobe and rammed earth. Protection from humidity is crucial, the word goes: “having good boots, a wide roof and a coat”. Solid foundations and footing, probably with rocks and maybe with cement provide a base and protect against humidity, a wide roof and plastering protect against rain.
There is no good or bad material, just material well or badly used
Earthquakes bring terrible suffering, buildings collapse, people get killed or injured. If this happens in a culture with clay buildings, the commentaries trend to condemn adobe and rammed earth constructions, disregarding that also cement based structures have collapsed and killed. In recent years, Haiti 2010 and Ecuador 2016, large seismic events have hit areas where cement-based structures predominate, the death toll is huge. In both countries grupo sofonias and the ecosur network analyzed the situation and directed reconstruction programs in cooperation with the Swiss Development Corporation.
Haiti 2010, concrete building collapsed, old timber structure still standing
Most popular construction in the developing world is unsafe. Artisans learn from “masters” who themselves never received proper training and knowledge, the same errors are committed time again at the cost of the house owners and placing at risk the inhabitants. [3]
[3] ONE PLANET NETWORK, 2020, “Confined masonry for improved earthquake resistance”
Ecuador, 2018. Confined masonry.
Based on the long-time experience of grupo sofonias with dual education, training for “empirical builders” was organized. They received formal classroom education, combined with practice while building houses. In cooperation with the Swiss agency and local universities, excellent education material was developed and used in the classroom and on site. [4] More than hundred masons and carpenters acquired solid theoretical knowledge and put it into practice, finishing with an exam and diploma.
[4] SDC et al, 2017, “Guía para la construcción de viviendas sismo-resistentes en mampostería confinada”
Dual education for builders.
Some basics on resilience against earthquakes
Earthquakes place multiple stress on buildings, it is mainly the horizontal solicitations that cause damage and potential collapse. Masonry walls without additional reinforcements (e.g., timber, reinforced concrete, metal etc) might suffer cracks because masonry has generally good resistance to compression, but weak flexural strength, this is particularly true for earthen walls. Depending on the direction of the seismic waves, some walls suffer mostly diagonal cracks and on the other side vertical ones.
High walls will be more affected, mainly if they are slim, second and third floors run higher risks. Traditional buildings usually are built with thick massive walls, often with horizontal reinforcement and might have withstood several sizeable quakes. Maintenance and repair is the key to resilience.
Reinforced concrete opened new possibilities and today most popular dwellings are built with a grid of columns and beams, so called reinforced masonry. The walls are often left open for business spaces or garages and in the upper floors they are filled in with any material without real bonding to the structure. There are no solid walls that could take the shearing forces in a seismic event. It is common to find buildings where the ground floor has collapsed under the weight of the upper floors.
By introducing the change from reinforced masonry to confined masonry, the walls will respond to the shearing forces, acting together with the concrete structure. The basic step is, to build the walls first and fill in the columns and beams afterwards to make an almost monolithical unit and to assure in the design state that there is a good balance of solid walls and open spaces.
Confined masonry, brick walls and concrete columns indented.
The ecosur network
The core members of the network accumulate wide knowledge and experience in designing and implementing social housing projects, specifically after disasters. From Guatemala 1976 to Ecuador 2016, thousands of buildings in different local materials are one result, also hundreds of properly educated and trained builders. Architects and Engineers have passed on their knowledge as project designers, managers and instructors in post disaster situations in Asia and Africa.
Ecosur is eager to assist programs to improve the popular building knowledge. Sustainable housing has to be affordable, small ecological footprint, respect the culture and be socially desirable.