the world based on climate appropriate building design and the availability of local materials. Adobe One of the oldest building methods, adobe is simply clay and sand mixed with water. Often, chopped straw or other fibers are added for strength. The mixture is then allowed to dry in the desired shape. Usually adobe is shaped into bricks that can be stacked to form walls. Various claims are made about the optimal proportions of clay and sand (or larger aggregate). Some say that the best adobe soil contains 15% - 30% clay to bind the material together. Others say equal proportions of clay and sand are best to prevent cracking or fragmenting of the bricks. The blocks can either be poured into molds and dried, or pressed into blocks. Adobe colored with clay and polished with natural oil makes an attractive and resilient floor. To protect the walls and reduce maintenance, adobe buildings usually have large overhanging eaves and sizeable foundations. Adobe can be plastered over with cob or lime-based mixes for both appearance and protection. Adobe has good thermal mass, meaning that it is slow to transmit heat or cold. It is not a good insulator, however, so insulation can be added (preferably on the outside), or a double wall built with airspace or insulation in between. The traditional thick, un-insulated adobe has proven to perform best in regions without harsh winters or where daily sun is predictably available during those cold periods. Bamboo Bamboos are some of the fastest-growing plants in the world. Bamboo can be utilized as a building material for scaffolding, bridges, houses and buildings. Bamboo is a natural composite material with a high strength-to-weight ratio similar to timber, and its strength is generally similar to a strong softwood or hardwood timber. In its natural form, bamboo as a construction material is traditionally associated with the cultures of South Asia, East Asia, the South Pacific, Central and South America. Cob The term cob is used to describe a monolithic building system based on a mixture of clay, sand, straw and earth. The construction uses no forms, bricks or wooden framework; it is built from the ground up. Various forms of "mud" building have been used in many parts of the world for centuries, under a variety of names, and date from at least 10,000 years ago. Cob building began use in England prior to the 13th century,