EcoSur: Concrete Roof Tiles, puzolanic cement, earth houses, ecomaterials

Experiences to learn from a reconstruction in Adobe in Baja Verapaz, Guatemala

Recurring natural disasters tend to capture the public attention, but sometimes little is learned from successful reconstruction experiences. Thus, we wish to highlight a post-earthquake reconstruction project in Guatemala after the devastating earthquake of February 4, 1976, a project that has withstood the test of time and several strong earth tremors.

After the earthquake, that caused the death of some 24,000 persons and destroyed more than 250,000 houses, clay construction was considered unsafe and the national government was considering a ban on “adobe”, the traditional clay construction technology widely used in Guatemala.

This project concentrated on the Department of Baja Verapaz, a hard hit area in the centre of the country, somewhat off the beaten track, where no other agency was supporting reconstruction projects. It was a practical education program to demonstrate that possibilities do exist that could improve the security of adobe houses while keeping costs within the reach of the poor majorities. A team of adobe-builders was trained and in dozens of outlying villages as well as in the neighborhoods of the small towns a total of 150 houses were built in guided self-help.

In a nutshell, it was reconstruction in a sustainable manner, concentrating on setting examples of earthquake resistant houses that are affordable to the general public.

The project was impulsed and totally financed by Caritas Switzerland. The major beneficiaries were 150 poor families who had lost their homes in the earthquake. Moreover, 18 masons who learnt a new trade also benefited, with several of them later working as village masons, benefiting more poor families with affordable and safe constructions.

The project was based entirely upon popular participation. The “new” ideas about building with adobes, but improving the technique and workmanship did not find much enthusiasm at the beginning and, therefore, a careful and slow build-up of confidence was needed. Through this process a deep commitment to the project developed with many of the beneficiaries and all organisational decisions were taken in the management group that was composed of beneficiaries and masons with the project manager being the only outside person included.

24 years later, Caritas Switzerland and Grupo Sofonias have financed an evaluation of the project, which was conducted by an Engineering Professor of the national University together with three undergraduates of Architecture and Civil Engineering.

The Evaluation after 24 years

The evaluation team visited 43 of the 150 houses built in the project, in urban Salamá, San Jerónimo and San Miguel as well as in outlying villages of those three municipalities. They concentrated on the following aspects :

• The social impact this project has had
• The physical state of the buildings after 23 and 24 years of use
• Evaluate the convenience of repeating this type of projects for earthquake prone areas.

The technical evaluation was comparing the results to the instructions given by the technical manual that had been produced by Caritas Guatemala in 1976. [1] This manual has been widely used as reference document in many adobe projects throughout Latin America, it has been based on a UN-sponsored investigation after the 1970 earthquake in Peru. [2]

The social impact

In the interviews, many of the house owners manifested that the project has helped to unite the community and that neighbourly relationships were improved through the project. 72 % of the surveyed houses are still in the hands of the original beneficiaries. Many manifested that after the earthquake they were afraid of adobe, but today they feel comfortable and happy to have their adobe house, only 7% of the interviewed would prefer another technology. Many young people living nearby spontaneously asked to be considered for a similar project in the future.

Only few have seen the necessity to add to their houses and they generally have been using the same materials and techniques as in the original house. It has been observed that the technology used was copied by neighbours. Only one house is abandoned, it was destroyed by a torrent during hurricane “Mitch”.

The state of the houses

The technical evaluation found mostly positive aspects, but also some negative points.

The foundations were always done in cyclope concrete (stones embedded in lime-cement-sand mortar), they are generally in good state, however some have been partly eroded by water, which is a problem of lacking maintenance. Only one was seriously damaged through the action of tree roots.

The project always built a first layer of cyclope concrete on top of the foundations to avoid the adobes touching the ground. This generally serves its purpose, though in some cases the adobes still get some humidity. It has to be noted however, that the evaluation was done in the rainy season.

The adobe walls do generally show some wear and tear, mainly the ones that are not plastered. Some erosion through wind and rain, but also by wasps who drill their holes into the wall can be noted. The walls that are plastered with a layer of clay and sand and then with a smooth lime finish are mostly in good conditions. About half of the walls showed some varying degrees of humidity.

The walls have a thickness of 40cm, with square bricks and half bricks, and in all corners they use cross buttresses made with the same adobes. Technically it is clear that those measures augment the safety against earthquakes, and in the interviews with the house owners it was found, that the buttresses are considered by them a very important improvement in security. This obviously was and is an important psychological fact.

The adobe manual stresses the fact that the mortar between adobes should not exceed 20 mm. This treats an error made by most adobe masons and also in the project it has not been eliminated totally, it was observed that mortar joints exceeding this thickness are often cracked. Generally it can be said, that the state of the walls is very good, and the few cracks with certain structural importance do not endanger the security of the house. The clay used is of good quality and even the walls that are not plastered are in good conditions. It is interesting to note, that houses are generally only plastered on the front side, only 3 houses were also plastered inside.

A ring beam made of reinforced concrete was placed on top of the walls. They are in perfect conditions in all houses, often they are at the same time the window- and door beams. It is considered that this element is of singular importance for earthquake safety, as it is largely able to distribute the horizontal solicitations of a tremor.

The people were given the choice between a roof of galvanized iron sheets or traditional clay tiles. In the aftermath of the earthquake metal sheeting was favoured, but step by step the tiles made their way back and in the last 20 years many people seem to have replaced sheets with tiles. The under structure is always made of timber, partially combined with canes. Most of the wood is still in good condition, although some of it is affected by insects or fungus.

The structural design is good, the ridge is always supported by a dividing wall. This augments earthquake safety considerably as it is well known that many walls collapse as a result of a defect roof that pushes the walls out. This is mainly true for heavy tile roofs.

Most floors were initially made with burnt clay bricks. However, over the years many families have substituted them with concrete floors, 82% of them have some cracks.

The convenience of promoting such projects

The evaluation team came to the conclusion that it is possible to build houses with traditional clay technologies in seismic zones, if the necessary improvements are made. It is strongly recommended to plan and organize such projects in harmony with the culture and idiosyncrasy of the population and surrounding nature, as well as with the traditional architectural expressions.

Conclusions and recommendations of the Evaluation

• The condition of the 24 year old houses generally is good. The difference between them are due to different degrees of maintenance and differences in their location.
• From an architectural point of view the project is a success. Good social integration combines with a good inclusion in the local culture and environment.
• The structures have behaved well under horizontal solicitations, the project is located in a seismic zone and the houses have withstood several tremors of considerable force, including the recent earthquakes which devastated parts of neighbouring provinces in Salvador and Mexico.
• We would like to recommend the realization of this type of projects where local materials are used and a harmony with the identity of the communities are created. They have to be accompanied with an education program for maintenance.
• All houses with present damages are reparable. It is interesting that the level of maintenance does not differ in rural and urban environments. It is recommended to prepare educational material for maintenance and include this in future projects.
• Humidity is sometimes a problem in the houses, mainly the ones without outside plastering and specially the ones without eaves trough . Adequate plastering would certainly diminish certain health problems like the „mal de chagas“ caused by insects. It is recommended to join efforts between practitioners and professionals to determine good practice in plastering clay walls.

The EcoSouth network considers this evaluation of high importance, as in neighbouring El Salvador a series of earthquakes recently has caused much destruction and the heated discussions on the safety of clay buildings is again underway. This same procedure repeats itself time and time again, and time and time again clay buildings are declared to be the worst affected. That this is not necessarily the case demonstrates a census taken by the Salvadorian Government after the disasters in January and February 2001, from where it can be deduced that clay houses were not worse affected than “cement houses” . [3]

A fact is that for many poor people in the third world clay is their only chance of building a decent house.

Most publications about “earthquake resistant buildings” propagate “improvements” that are either not proven, or are costly, or both. However, the authors of this project believe it is deficient workmanship and disregard of basic construction principles that cause the majority of failures in adobe buildings.

Therefore, the project concentrated on improving those deficiencies through practical and theoretical education as well as the construction of houses that are replicable (affordable) by the majority of locals without outside financing.

Bibliography:

There exist many books and pamphlets on clay construction. However, not all of them are based on sound practical or scientific experiences and facts. Also, it has to be taken into account for what social, economic and climatic circumstances you plan to use clay as a building material. There exist excellent technical materials on rammed earth construction in Central Europe (Dachverband Lehm, www.dachverband-lehm.de) and on adobe for the southern USA (Adobe builders network). A standard on clay construction, including clay-cement mixtures is “Earth contruction” by CRATerre (ISBN 1-85339193-X). However those technologies are not likely appropriate for the general use in the third world and the project in Guatemala worked with “natural adobe”.

Building with clay on a popular level is as much a question of philosophy as of technology, and the major reference book on this, which should be read by anybody directing clay projects, is still “Architecture for the Poor” by Hassan Fathy (University of Chicago Press, ISBN 0-226-23916-0 [KR1] ). Technical overview is best in “Building with earth” by John Norton (IT Publications, ISBN 1-85339-337-1). There exist many practical manuals, like the one produced by Caritas Guatemala, which is out of print, but will be republished by the EcoSouth network (www.ecosur.org) or “Vivienda de ladrillos de adobe” published by gate (www.gtz.de/basin), based on the Caritas manual. “La casa de adobe sismoresistente” (ISBN 99923-25-16-X) published by “Equipo Maiz” in Salvador is also based on the same concepts.

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[1] “Manual para la construcción de viviendas con adobe”, Caritas de Guatemala

[2] Proyecto experimental de Viviendas (Ministerio de Vivienda – Naciones Unidas, 1971)

[3] Gabriel Pons, “La tierra como material de construccion, June 2001

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[KR1]Publicado en español como “Arquitectura para los pobres”