C O N T E X T 1 4 3 : M A R C H 2 0 1 6 11 MARIA YIOUTANI-IACOVIDES Vernacular earthen architecture Earthen material, used in vernacular architecture worldwide for centuries, could have enormous potential for building with local resources in an age of climate change. Earth is a gift bestowed to mankind by nature to be used as a building material, and it has been, since the neolithic era. In 2004, 563 world heritage sites listed by UNESCO were built entirely or partially with earthen material. In 2012, 150 were added, and more are to be included in the future. In the 20th century half of the Earth’s population lived in earthen buildings. In the 21st century there is a growing interest in the material’s ecological properties and its use as a contemporary building material. In the UK, it is traditionally known as cob, or wattle and daub. It is even better known for its widespread use in hot and dry climates. Earthen material’s global and timeless use provides a strong incentive to investigate its history, indigenous styles, performance, structural techniques and potential. In Cyprus, archaeological excavations have unearthed mudbrick structures in settlements (Kalavasos and Khirokitia) from the Cypriot Aceramic neolithic era, dating from 7000 BC. In the UK, earthen material was used in part for the construction of Hadrian’s wall. In hot and dry climates, we have even more impres- sive structures. In ancient Mesopotamia (modern- day Iraq), high-quality clay made up the mudbricks that were used in the construction of Ziggurat (6th century BC). In Egypt, the fertile soil near the river Nile was used to build one of the finest examples of mudbrick construction, the vaults in the Ramesseum (1250 BC) inThebes (Luxor). InYemen, the old city of Shibam (16th century AD) has the world’s first high-rise buildings, built of mudbricks. Earthen material was used through the centuries to build simple single-storey dwellings, fortifications and mud skyscrapers. Indigenous styles and ingenious creations reflect natural and social parameters. These provide us with examples that come from continuous refinement. In the mountainous regions of Mali, nomads have built their earthen huts on hill slopes, with thatch umbrellas and raised floors, allowing water to flow underneath the structures during storms. The densely populated earthen built villages in Draa valley, Morocco, have flat rooves which become a living space, a path or part of the street. The indigenous integrity and authenticity have allowed endless creativity (shapes, forms, colour) in the plasticity of the forms. Decoration becomes a method of conservation and preservation. In Nigeria, some dwellings have decorative, protective coating: a thick layer of lime or juice from local fruits is used as a waterproof finish on the walls.The coatings are renewed annually, in a ritual that follows the rainy season. In Mali, dwellings have decorative geometrically shaped openings to provide ventilation. In Saudi Arabia, the tall, earthen dwellings have layers of slates to protect the monolithic structure from shrinking in rainstorms. Earthen material’s performance, attributes and qualities are remarkable. It is economical, immediately available, inexpensive and easy to use. It is ecologically sound: a natural material, reusable, durable, degradable. It has excellent thermal qualities (cool in summer, warm in winter), and it is both soundproof and fireproof. Its seismic attributes are notable: it is flexible and behaves well under compression. Seismic performance varies according to the structural technique used. Being an organic material, it has low fracture resistance and its greater enemy is water in its several forms, particularly rainwater or rising humidity. Its shear-force resistance needs to be improved by enhancing its structural qualities and achieving equilibrium. The vernacular builder, who was usually the user, was aware of the material’s potential.To avoid the material shrinking, he or she followed the principles of the buttress-type loadbearing wall, which creates central thrust against bending.The walls grow thinner as the building rises, or the walls are buttressed, as in the construction of ziggurats.The walls are tied up with bonding timbers to achieve horizontal reinforcement. A three storey earthen building in Nicosia, Cyprus. Despite neglect, the earthen structure is in sound condition.