“Every people that has produced architecture has evolved its own favorite forms, as peculiar to that people as its language, its dress, or its folklore. (...) and the buildings of any locality were the beautiful children of a happy marriage between the imagination of the people and the demands of their countryside.”
(Hassan Fathy, Arquitectura para os Pobres, (1973), ed. 2009, p. 31)
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1.1. Introduction
Earthen architecture is a generic term (adopted since the 4th International Symposium on Mudbrick Preservation, held in Ankara in 1980) that comprehends all construction built with raw earth (Houben and Guillaud 2006). It is considered one of the most diverse and widespread types of architecture in the world since it exists in almost every continent, and it varies from modest houses and settlements to imperial cities, fortresses, mosques, churches, and even “skyscrapers” (Correia 2016).
Earthen construction is also a common designation when building with earthen materials.
Due to its apparent simplicity, earthen architecture is commonly associated with lower social classes or developing countries. A very important Egyptian architect – Hassan Fathy (1900-1989), quoted above – dedicated a book entitled “Architecture for the poor” to this topic, exploring earth as a material with huge potential and with an incredible history of construction evolution, removing the prejudice associated with this type of constructions and giving it a modern approach, but always respecting its traditions (Fathy 2009).
Looking at the world map depicted in Figure 1.1, the distribution of earthen buildings is more related to climate conditions and material availability rather than to the social status of the place. It is possible to see earth used as the base material in vernacular houses, but also in monumental heritage buildings, and even in contemporary architecture.
Figure 1.1: Earthen construction distribution worldwide (credits (Alex 2018)).
It is estimated that around 30% of the world population lives in earthen buildings [1] [5], although this number may vary according to other authors. Fontaine and Anger claim that the value is closer to 50%
(Fontaine, Romain Anger, and Houben 2009) and also Costa et al. (Costa, Rocha, and Velosa 2016) state that nowadays the 30% value is no longer updated, being probably a larger number. Considering
3 the case of developing countries, more than half of the inhabitants live in earthen houses, more concentrated in rural areas, and at least 20% in urban areas (Houben and Guillaud 2006). Moreover, in developed countries, earthen construction gained more projection as an alternative to face economic and energetic crises, as happened in the United States, where adobe and rammed earth (two common construction techniques) have state codes and regulations for construction (Lima, Marques, and Pimenta do Vale 2016). Also, new studies showed that earth buildings have excellent acoustic and thermal conditions (Correia 2006).
Contemporary architecture plays an important role in the development and dissemination of earthen heritage. The importance of rethinking cities into more organic and sustainable processes to guarantee their existence for the next generations is no longer a concern of the future, is a present need. Using local and available materials, with lower carbon footprint and lower resources consumption is exactly the description of ecological construction, where the category of earthen buildings fits perfectly. Furthermore, fortunately, there is no need to reinvent all from scratch, because earthen construction is a living heritage, in the sense that most of the techniques are still used nowadays and continue to evolve, adapting to each place and environmental conditions, and contemporary materials since it is possible to add stabilizers and additives that improve the local soil characteristics and consequently the building itself.
An interesting exercise is to compare earthen buildings with other ancient construction materials, as the case of stone and wood. Due to higher resistance and durability, stone and wood were usually reserved for important buildings, even though construction time was longer because of transportation and preparation complexities. Looking specifically to stone monuments, it is impressive the work done through time by mankind since prehistoric times, like the megalithic complex of Stonehenge, where stones with more than 20 tons are in vertical position; or the precise technique of masonry walls and buildings of Inca culture, with its stones cut with very high accuracy to fit in each other; or even the meticulous and complex work of stone Gothic cathedrals. However, these techniques are no longer used as before. The fast growth of the world population associated with a change in society's paradigm led not only to a loss of interest in these construction techniques but also in a loss of knowledge on how to do it. On the other hand, as previously mentioned, earthen buildings are an alive source of expertise and information, in the sense that there are people who kept their traditions, passing it through generations, and reaching nowadays. And because “heritage” is not only the monument but all that surrounds it, from material to immaterial aspects, to cultural impact on a place and society, and all the intrinsic values of use, property, and significance, it is crucial to preserve it as a combination of all of these factors. That is why this important know-how should not be neglected and should be used as a foundation for any study related to the preservation and continuity of this legacy.
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In the First International Workshop on Earthen Architecture held in the World Heritage City of Yazd, Iran (February 2019), Jukka Jokilehto (ICCROM) referred to the concept of looking at heritage as a whole and not just the monument itself. There are several aspects to be considered when dealing with heritage preservation, as culture creativity, environment context, economic management, community appreciation, integrity, identity, and meaning. In the same workshop, also Thierry Joffroy (CRATerre-ENSAG laboratory) mentioned his experience in different earthen heritage interventions in Africa, where the involvement of the population is essential to design the conservation program. In these places, maintenance is done by local people and typically using natural products, not only because of their efficiency and availability, but also because of significance. This is the case of Mali, where the final plaster and paintings done on earthen monuments and houses are meant to be sacrificial layers with symbolism associated with the desire for rain. All these concepts are more present in earthen heritage because of the already mentioned fact of being an alive form of inheritance, and in some countries, very close to their population. That is why it is critical to involve more the conservation science community in these interventions creating a holistic approach to the subject and more bridges between different study fields. However, more research is needed to understand deeply degradation processes, degree of durability, and reinforcement techniques to produce codes and standards that may assure earth as a valid and necessary material not only to preserve, but also to use in present construction.
1.2. Motivation
This research work started with a question: Are conservators doing enough to preserve Earthen Heritage? And, as in any other case, immediately after one question, several more questions follow:
What methodology approach has been used for conservation projects in earthen heritage? How is conservation science involved in these types of projects? What research regarding conservation procedures and material degradation has been done? What products are being used? What is the opinion of specialists working with earthen constructions and heritage about the commonly applied conservation methodologies? Among all these doubts, an idea began to gain shape – learning more about earthen heritage and try to develop conservation guidelines to be applied to it.
The interest and fascination about vernacular architecture started many years ago when working as a volunteer in the North of Portugal (Trás-os-Montes region) restoring vernacular houses. In that period, a lot about construction techniques and traditional materials with local people was learnt, allowing immersing in the communities, and absorbing as much knowledge as possible. After one year, this experience helped to develop a deeper respect for the ancient know-how and its empirical application and, most important, to understand how all this knowledge can still be used and should never be
5 neglected. By continuing working on different conservation projects in historical monuments, the previous questions kept on appearing. And with some ideas in mind, it was time to go back to research and develop a Ph.D. on earthen heritage conservation.
1.3. Research goals and methodology
Based on the literature review, it was possible to identify three main aspects clearly deserving deeper research regarding the conservation of earthen heritage. These three points became the key goals for this work:
1) The definition of earthen heritage conservation.
2) The identification of methodologies applied to earthen heritage conservation.
3) The characterization of the products used in the conservation and restoration of earthen heritage.
Within these three main goals, it was established a set of sub-topics to develop during the project, to create a solid research program. Table 1.1 reports the goals and sub-categories identified as main topics to develop during the project. Regarding the first topic (definition of earthen heritage conservation), the main objective is to underline the importance of having a multi-disciplinary approach when dealing with earthen constructions. The fact that this type of buildings requires specific attention and research from different areas means that it is essential to involve more the conservator-restorer and the conservator-scientist in these projects. One of the biggest concerns regarding the preservation of these monuments is the lack of a holistic approach. Therefore, for this topic more attention will be given to conservation theory, providing solid bases for any intervention in earthen heritage.
Table 1.1: Goals and sub-categories of the thesis plan.
Definition of earthen heritage conservation
Identification of methodologies applied for earthen heritage conservation
Classification of the products used in the conservation and restoration of earthen heritage
→ Importance of earthen heritage preservation.
→ Conservation theory.
→ Role of the restorer and conservator-scientist.
→ Importance of multidisciplinary teams.
→ What is conservation methodology?
→ Identify the methodology or methodologies used in earth heritage conservation.
→ Discuss the importance of the methodology plan in an intervention in cultural heritage.
→ The need to draw a new methodology.
→ Review ancient products/recipes.
→ Identify products used nowadays.
→ Select suitable natural and synthetic products to test.
→ Test products under laboratory and in situ conditions.
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In what concerns the second point (methodology applied on earthen heritage conservation), it will be addressed the value of having a methodology or guidelines to follow in any conservation project. After gathering information about which methodologies are applied on earthen heritage projects worldwide (known case studies), the goal is to understand if there is homogeneity in these procedures and which theories and methods have been followed. With a critical perspective, this work intends to highlight the need for new guidelines based on the collected data and on the urgent challenge to adapt the conservation projects to contemporary logics. An approach for a new methodology based on a sustainable strategy will be suggested, having as background the lessons from the traditions of earthen heritage preservation – using of local and natural products.
Finally, for the third point, the main goal is to collect recipes and products used for conservation procedures on earthen architecture. These products will be of natural and synthetic origin and they should be used nowadays. After the selection of some products and procedures, they will be tested under laboratory conditions in terms of compatibility, efficiency, and durability.
Given the above, the main objective of this thesis is to understand the possibility of using more natural-based products to preserve earthen heritage, instead of synthetic ones, in order to define a greener strategy as a methodology for conservation. This idea summarizes all three topics and provides the base for this project – test alternative natural products, with a conservation science approach, to define new guidelines for earthen heritage interventions.
Finally, this thesis is expected to create more awareness of the importance of earthen heritage and its preservation, as well as to bring the conservation science into this topic, merging the scientific and the empirical approaches.
1.4. Thesis structure
The thesis is divided into seven main chapters: the first one is the Introduction, the second one is dedicated to the History and Technique of Earthen Construction, explaining how this type of buildings appear in different regions of the world, giving examples of monumental and vernacular architecture, and describing the different construction techniques, as well as the raw materials employed, their properties and differences. The third chapter is about Conservation of Earthen Heritage, where a literature review of what has been done so far regarding earthen heritage interventions is initially addressed. Then, conservation theory, the role of the restorer and the conservator-scientist are discussed, as well as the ethical principles of conservation as the base for any intervention. In this chapter, there is also a part dedicated to aspects related to the Methodology of Conservation, where the paradigm of contemporary interventions will be discussed to provide alternative guidelines towards a greener strategy. The fourth chapter is dedicated to Experimental
7 Work: Materials and Methods, with all material characterization and description of the used testing methods. The fifth chapter is the second part of the Experimental work: Results, where the results obtained from the laboratory research performed on adobe and rammed earth specimens are illustrated. The specimens were treated with different consolidants and water repellent products and tested in terms of efficiency, compatibility, and durability. In the sixth chapter the work done in the Case Study: Rammed Earth Installation is described and discussed. Finally, the seventh chapter is dedicated to Final Remarks and Future Work.
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