Characteristics of good timber are given below in the order of decreasing significance:
Strength
The timber should be strong enough to effectively act as structural members, such as joists, beams, rafters, etc. Further, it should be in a position to sustain loads applied gradually or suddenly to it. Preferably, the strength should be adequate in direct and transverse directions.
Hardness
The timber should be hard so that it is in a position to offer resistance when it is being penetrated by another body. As such hardness is imparted to the wood by chemicals present in the heartwood and the density of wood.
Fire-resistant
As timber is a bad conductor of heat, it should be dense enough so that it resists fire. A good timber should not contain resins and other inflammable oils since they accelerate the action of fire.
10.4.4 Structure
It should possess a uniform structure. This is ensured when there is firm adhesion of fibres and compact medullary rays. Further, the annual rings should be regular and closely located.
Elasticity
This is the property of a material which returns to its original shape when the load causing the deformation is removed. Timber should possess this property, as it is essential when timber is used for bows, carriage shafts, etc.
Durability
Another important quality required for timber is it should to be durable. It should have a long life. It should be capable of resisting the actions of fungi, insects, chemicals, physical agencies and mechanical agencies during its lifespan.
Defects
It should be free from defects such as shakes, flaws, dead knots or blemishes of any kind.
Weight
Quality timber should be of heavy weight and uniform along the length under consideration.
Fibres
Good timber should possess straight and close fibres, which signify uniformity in the timber.
Workability
The timber should be easily workable, i.e., it should not clog the teeth of the saw. It should be capable of being easily planed. A good timber when planed shows a firm and bright appearance with a silky lustre.
Colour
The colour of quality timber should be uniform and of dark colour. Light-coloured wood usually indicates timber of low strength.
Sound
Good timber should produce a clear ringing sound when struck. Decayed timber produces a dull and heavy sound.
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