First and foremost let me point out that,Timber is an important building construction material, used widely as scaffolding, walling, flooring and roofing material. It’s produced from harvested trees –not just any tree, but from a select group of trees known to yield good timber that is suitable for the built environment. The harvested trees undergo a series of processing that eventually convert them to timber, that can be purchased at Timber yards.
Second, Timber is made up of cellulose, hemicellulose and lignin which are natural polymers. These three substances combine to form microfibrils which in turn are the building blocks for timber cell walls. Millions of these cell walls and fluids constitute Timber as we know it. The three natural polymers give wood its strength, with cellulose contributing tensile strength and hemicellulos and lignin providing compressive and elastic strengths.
Timber also contains water, resins, gums ,tannins and occasionally inorganic material like silica. Fungi is also to be found in timber attracted by presence of starch which it feeds on.
Hardwood and softwood
Third point is that ,Timber is classified as hardwood or softwood based on their botanical categorization-(that is scientific classification of plants) and not their physical strengths. It follows, but somehow amusing, that the term hardwood timber does not necessarily mean the timber is strong and durable. And the converse is also true. For example Balsa timber is a hardwood but it’s soft and used to make models. And on the other hand, Yew is a strong and durable timber but is classified as softwood. That is why it’s important to know precisely the tree from which the softwood or hardwood was harvested, in order to minimize disappointments.
Hardwood (angiosperms) are defined as timber harvested from broad leafed trees, which are mostly deciduous (shed their leaves seasonally).And softwood (gymnosperms) are conifers-they produce cones containing its seeds, has long thin needle like leaves and stays green all year round. Softwood trees do not lose leaves seasonally with exception of European Larch. Microscopic examination reveals that the softwood and hardwoods have completely different cellular structure.
The following are example of trees that produce softwood timber is used in building and construction.
- Californian redwood-the world’s largest tree with height of over 100 meters.
- Eucalyptus (Gum tree)-They are originally from Australia.
- European Larch.
- Parana pine.
- Pine (European redwood).
- Pitch pine.
- Spruce (European whitewood).
- Western hemlock.
- Western red cedar.
For trees that give us hardwood timber the following examples will do:
- Ash-It a tree with smooth pale brown to grey bark. It produces a tough hardwood that absorbs shocks without splintering.
- Beech-They are large trees with smooth grey barks.
- Elm-They are large trees with round leaves.
- Mahogany-They are trees that produce hard brown –red timber that is highly valued. The Mahogany timber is used to make high quality products. The tree can live for over 350 years.
- Maple .It is a deciduous tree with wide leaves and produces a hard creamy-brown timber.
- Oak-Oak are large trees that can live for over 1000 years.
- Sweet Chestnut-They are tall trees with large wide leaves that produce red-brown nuts.
- Teak-They are large deciduous trees with yellow-brown wood. This wood is one of the most valuable timber, lasting for hundreds of years .These trees are native to India, Myanmar and Thailand. Among other applications, they are used in shipbuilding and flooring.
- Walnut-They are deciduous broad-leafed trees and their best wood is at the base; as result they are often dug up for their timber.
Moisture content and Seasoning.
The fourth amazing fact is, Timber can absorb and lose water. The controlled loss of moisture from green timber to a desired level for use in a specific location is a called seasoning. Seasoning help to stabilize the moisture content so that it equal to moisture content in the surrounding atmosphere. After seasoning any subsequent loss or absorption of moisture is usually of no consequences.
Poor seasoning may lead to rapid loss of moisture that may cause the outer layer to shrink while the inner layer is still full of moisture. This may cause timber to curve, twist or crack.
Seasoning can be by air which is a slow process that can put your patience to the test or by Kiln which happens to be faster and may take few days for the timber to be ready for use.
In conclusion ,Timber is used as softwood cladding, hardwood flooring ,Pile foundation as an alternative to concrete, in roofing for trusses, roofing covers as shingles or shake(using red cedar timber) ,Thatching (using reeds/barks or needle grass )and for timbered walls.
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Sources:Materials for Architects and Builders by Arthur Lyons PhD.