3. Building materials in the hot climate zones

Cane and leaves are available in the warm-humid zones and grass in the intermediate and subtropical zones. Vine, bamboo and palm - fronds are used for buildings in the warm-humid zones. Because these materials are light, do not store heat, and allow the free passage of air. However, they have a relatively short life span because they deteriorate rapid­ly due to termite attack. They are also highly combustible.

Both hardwoods and softwoods are found in most tropical and subtropical areas with the exception of the hot dry zones. On exter­nal woodwork preservative stains should be used rather than paints which tend to deteriorate fairly rapidly in the hot zones. Extremes of climatic conditions cause dimensional changes producing cracks, splits and warping. Wind-blown sand and grit gradually erode ex­posed timber. In warm-humid zones timber is liable to wet and dry rot and to attack by termites and beetles.

Earth is one of the most widely used traditional building materials in hot-dry lands. Earth is used not only for walls but also for roofs; mud brick vaults and domes are common in countries like Iran and Egypt. Because mud has less strength than most other construction materials, mud walls are built thicker. Such rooms are much cooler in hot climates than those of any other material.

Concrete and reinforced concrete are widely used throughout the non-temperate zones. Cement is manufactured locally in many places. Sand is found almost everywhere but it may be contaminated with soluble salts. Suitable aggregate may be difficult to find. Con­crete is most frequently used for the structure, foundations and floor slabs of buildings. (1700 signs)

4. Why do we build?

We build because we need shelter. We need shelter from sun, rain, wind, and snow. Our activities mostly take place indoors. For these activities we may need air that is warmer or cooler than the air outdoors. We may also need less light by day and more light by night.

It is a well-known fact that modern people in many countries also need services. Modern services must provide energy, water, communica­tions, and dispose of waste. Sanitary accommodation is also necessary and very important. For sanitary accommodation people must have ventila­tion. All services and accommodations are pre­planned and located on a site plan. A site plan must be prepared and pro­vided for every building and every construction.

Modern civil construction has many branches. The main branches are housing construction, construction of industrial enterprises, construction of railroads, highways, subways, construction of bridges, dams, ports, canals, construction of different sporting facilities. Among them there are stadiums, aquaparks, swimming pools, sporting complexes, and others. (1000 signs)