Housing and Space Management

Housing And Space Management 3(2+1)

Lesson 21 : Building Materials

Characteristics Of Building Materials

1. Natural materials
   

   Mud:
   It is the most commonly used material in the house construction. Ever since man felt the necessity of a house, mud is widely used. Its main features are as follows.
   

   • Abundantly available natural material.
   • Cost is cheap.
   • Easily made and repaired.
   • Sufficiently lasting.
   • Maintain equitable temperature both in winter and summer.
   • Highly useful for low-income people. The use of mud mixed with chopped straw and cow dung helps for coating the inner and outer walls of the house. A thin coating of mud and cement maintain the surface in a good condition.
   
   
   

   Stone:
   Stone is a natural material of construction and is obtained from quarries. Since prehistoric days, it has been used for

   • Constructing different components of buildings like foundation, walls, lintels, floors, roofs etc.
   • The stones used for foundation and walls should be sound and free from cracks and decay.
   • Stones of different forms such as granite, marble, slate, sandstone and limestone are commonly used as building materials.
   • Waxing and polishing make them more attractive.
   • Gravel which are stones not larger than 2 cms is essentially needed for building. Care should be taken in using proper sizes of stones and correct inter locking in the width of walls.
   
   
   

   Sand:
   It consists of small grains of silica and is formed by the disintegration of rocks caused by weather. Sand should have the following qualities.

   • It is hard, durable, clean, free from organic matter and does not contain appreciable amount of clay
   • It should not contain harmful impurities such as iron pyrites, salts, Coal, mica, alkaline or other materials, which will affect hardening.
   • This should be coarse, clean, hard, strong, uncoated and free from clay, dust, mica and soft flanky particles such as of shell.
   • Sand required for mortar for brick – work needs to be sieved through a 3/8 in. Mesh sieve.
   
   
   

   Surkhi:
   

   • Where sand is not available or is very costly, surkhi is substituted in preparing lime mortar. It generally consists of crushed brickbats. When these are not available in large quantities, round balls of clay are made, burnt into kiln and crushed or ground to fine powder.
   • Crushed stone is also used but it should be free from excessive proportion of very fine particles like dust.
   • The best surkhi is made of clays containing 10 to 20 % of lime kunkar and this should be under burnt. Clay containing little or no lime must be thoroughly burnt to bring out the excellent quality of surkhi from it.
   • Surkhi should not be used in lime mortar for plaster, since it is likely to disintegrate after a time due to destructive agencies of atmosphere.

   Lime:
   

   • Lime has been used as a cementing material since time immemorial. In India till recently, lime has been extensively used for all types of construction purposes. Big palaces, forts, monuments, temples, bridges that were constructed centuries back and that still exist in good condition substantiate that the use of lime for constructional purposes had reached perfection in the past.
   • Lime mortars have some advantageous properties like good workability, plasticity, less shrinkage on drying and durability.
   • Lime is cheaper and easily available, even though cement has replaced the use of lime.
   
   
   Asbestos :
   
   • It is available in nature as a mineral in Marwar , Garhwal (Uttar pradesh) and Bhandra in Madhyapradesh.
   • It is silicate of calcium and magnesium found in the form of very thin fibres which are elastic and capable of being woven into fabrics.
   • It can withstand high temperature and acids without any change. It is used for roof, bathroom doors and partitions.
   • However it is not advisable to use asbestos as a roofing material essentially in our country since they transfer heat.
   
   
   

   Leaves
   Grass, palm leaves and Palmyra leaves are used for roof structure. They are temporary and highly inflammable.

   Wood: It is the nature’s most abundant useful building material.
   
   • It is comparatively inexpensive, strong, durable and easy to work.
   • Mainly wood is used for paneling, ceiling, roofing, partitions, doors, windows and for making veneers and plywood.
   • Plywood is made of odd number of woodpiles or layers laminated with plastic resins under high temperature and pressure.
   • It is used for doors, cupboards and decorative paneling.
   • Deodar, teak, mango, jack, toon, mahogany and bamboo are some of the common Indian timber trees used for building purposes.



2. Man-made Materials
   Cement: Cement should be used for the purpose of durability and strength of buildings.
   
   • It has the quality to bind together loose particles of gravel, broken stones or other aggregates.
   • Its quick setting property, strength and ease with which it can be used under variety of conditions has revolutionized the concept of construction.
   • Hence it has become the most popular cementing material.
   • Concrete is a building material made by mixing cement, sand, gravel land water, which becomes rock hard, when dry and set.
   • It is fire proof, sturdy and can withstand high pressure.
   • Because of these qualities, almost all huge structures are molded by concrete.
   
   
   

   Brick:
   The most extensively used construction material because it is locally available, cheap, strong, and durable and it has the good insulating property against heat and sound. It can be moulded to any shape or size. The standard size of bricks is 9” X 4 ½ “ X 3“, though the size varies according to local practice in India.

   The characteristics of a good brick are that
   
   • It should be so hard that it should not be possible to make a scratch on the surface with the finger nail,
   • It should give a ringing sound when struck
   • It should be heavy, and if allowed it should not absorb water more than ½ of its own weight
   • If kept immersed for two hours in water.
   • It should be free from any lumps and the most important test is that, if 5 or 6 bricks, selected at random, be kept immersed in water overnight, none of them should show a crack and a tendency to fall to pieces
   • If this happens, it may be assumed that the brick contains particles of lime kunker in its clay, which have been converted into quick – lime by burning. These bricks are unsuitable for work.
   • Colour of bricks is no test, because, it depends upon the nature and constituents of the clay and the fuel used for burning.
   
   
   

   Tiles:
   Tiles used for construction are of different types such as flooring tiles, country tiles and marble tiles.

   • The Country tiles and Mangalore tiles are generally used for roofing in rural areas.
   • Floor tiles consists of terrazzo, which are polished tiles made out of marble chips mixed with coloured sand.
   • Mosaic tiles are cement tiles polished with a portable machine after laying. Though they are expensive, they are easy to maintain.
   
   
   

   Metals:
   Metals and their alloys are the backbones of all engineering products used for construction. Metals used for construction can be classified into two categories.

   • Ferrous metals wherein iron is the main constituent. (e.g.) Cast iron, wrought iron and steel.
   • Non-Ferrous metals wherein iron is not the main constituent. (e.g.) Aluminium, Copper, zinc, lead and tin.
   • Iron and steel occupy the most important place in the construction of huge structures.
   • Steel is produced by combining iron and carbon chemically, heating it to red-hot and cooling it suddenly.
   • Steel is used as reinforcement in reinforced cement concrete.
   • Metal have great tensile strength and are lighter than wood.
   • Metals are both malleable (Capable of being beaten into any shape or rolledinto sheets) and ductile (Capable of being drawn into wires of variable thickness).
   
   
   

   Glass:
   Glass has been extensively used for glazing doors and windows, for insulation and for decoration.

   • Rapid advances in glass technology have opened up new avenues for its use.
   • Glass plate is heated and then suddenly cooled to temper it.
   • This tempered glass is much stronger and is used for glazing entrance doors, or in making table tops, shelves, counters, etc.
   • Glasses are also used for sound proof partitions.
   
   
   

   Plastics:
   Plastic have become a versatile material of modern times.

   • Plastics are available in a variety of forms to suit varied requirements.
   • It is fast replacing many conventional materials like timber, aluminium etc.
   • Plastics are used in electric and sanitary fittings like electric points, switches, holders, insulators, water closet seats and domestic furniture.