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BUILDING MATERIALSMaterials that are used for structural purposes should meet several requirements. In most cases it is important that they should be hard, durable, fire-resistant an easily fastened together. The most commonly used materials are steel, concrete, stone, wood and brick. They differ in hardness, durability and fire-resistance. Wood is the most ancient structural material. It is light, cheap and easy to work. But wood has certain disadvantages: it burns and decays. Stone belongs to one of the oldest building materials used by men. It is characteristic of many properties. They are mechanical strength, compactness, porosity, sound and heat insulation and fire- resistance. Bricks were known many thousands of years ago. They are examples of artificial building materials. Concrete is referred to as one of the most important building materials. Concrete is a mixture of cement, sand, crushed stone and water. Steel has come into general use with the development of industry. Its manufacture requires special equipment and skilled labour. Plastics combine all the fine characteristics of a building material with good insulating properties. It is no wonder that the architects and engineers have turned to them to add beauty to modern homes and offices. All building materials are divided into three main groups: 1) Main building materials such as rocks and artificial stones, timber and metals. 2) Binding materials such as lime, gypsum and cement. 3) Secondary or auxiliary materials which are used for the interior parts of the buildings. We use many building materials for bearing structures. Binding materials are used for making artificial stone and for joining different planes. For the interior finish of the building we use secondary materials. Natural building materials are: stone, sand, lime and timber. Cement clay products and concrete are examples of artificial building materials.
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