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Wood has been a highly used building material since prehistoric times. Among other highly used construction materials there are concrete, steel, brick, stone, and plastics. They all differ in their properties and in the methods of usage. Construction materials are known to differ in strength, hardness, fire- and corrosion-resistance durability, and, naturally, cost.
Being the oldest building material, wood is also known to be the only naturally growing organic material. Is wood strong? Hardly so, because wood always contains some water which decreases its strength. But after the wood is cut, the water content starts to evaporate and as the water content decreases the strength of the cut wood and its hardness start to increase. It is a well-known fact that the drier is the cut wood the greater is its strength and hardness.
Trees are known to grow naturally, which makes wood a constantly renewable natural resource. Among other advantages of wood there are its low cost, low weight, and high workability. But, as any other construction material, wood has its disadvantages. The main ones are the following - it is not fire-resistant, it easily burns. Besides, it easily decays.
Wood used for construction purposes is usually changed into laminated wood or wood panel products. Large structural wooden members are produced by glueing small strips of wood together.
Wood in panel form is more advantageous for many building purposes than boards. Why is it so? First of all, because wood panels are much easier to install than boards. They require much less labour for the process of installation. Besides, swelling (набухание) and splitting (расщепление) in panels are greatly decreased compared with boards. As to plywood panels, they are made up of thin wooden veneers glued together. It is of great importance to note that when wooden structures are designed the future stresses of their structural members must be predetermined.
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1. Does wood as a structural material have only advantages? If not, what are its disadvantages?
2. Is wood a strong building material? If not, why?
3. Does the water content in the cut wood increase or decrease?
4. What forms is wood changed into? And for what purposes? Compare wood in panel forms with boards. What do they differ in?
5. What elements are plywood panels made up of?