Table of Contents
Timber is defined as the structural wood that is used in construction or other engineering fields.
Even today, there is particular work where timber is considered the ideal member.
1. Types of Timber
Types of timber are explained below:
i) Standing timber:
It is the timber available in living timber.
ii) Green timber:
It is the freshly fallen tree that has not lost much moisture or timber which still contains free water in its cell.
iii) Rough timber:
It is the timber after falling off the tree.
iv) Converted timber:
It is the timber that has been sawn or prepared into various market sizes. Such as planks, Beams, Battens, etc.
v) Dressed timber:
It is the timber that has been sawn and worked to the exact required condition.
vi) Structural timber:
It is the timber used in framing and load-bearing structure.
vii) Clean timber:
It is the timber free from defects, deflects, and blemishes.
2. Exogenous Tree and Endogenous Tree
i) Exogenous tree:
Plant growth occurs by adding new cells around though grown in the previous year.
This process naturally resolves an increase in height as well as the diameter of the plant.
It grows with the addition of a concentric ring every year.
Timber obtained from this class of tree is extensively used in engineering work, Eg. Deodar, Saal, Shisham, etc.
ii) Endogenous tree:
Plant growth occurs by adding new cells only at the end of previous years. Such a tree grows upward without becoming much thicker.
The stem of this tree is too flexible, and thus they are not suitable for engineering work. E.g., Bamboo, Sugarcane, Coconut, Pine, etc.
| S.N. | Exogenous Tree | Endogenous Tree |
 |  | |
| 1 | Plant growth occurs by adding new cells around though grown in the previous year. | Plant growth occurs by adding new cells only at the end of previous years. |
| 2 | New materials are being added to the outer side of the bark. | New materials are being added up to the inner side of the bark. |
| 3 | An increase in height, as well as the diameter of the plant, is seen. | Such a tree grows upward without becoming much thicker. |
| 4 | Timber obtained from this class of tree is extensively used in engineering work | The stem of this tree is too flexible and thus is not suitable for engineering work. |
| 5 | Eg. Deodar, Saal, Shisham, etc. | E.g., Bamboo, Sugarcane, Coconut, Pine, etc. |
3. Characteristics of a Good Timber
~ It should have a uniform color.
~ A freshly cut surface should provide a sweet smell.
~ It should have regular and annual rings.
~ It should give a sonorous sound when struck together with each other.
~ It should have straight and closed fiber.
~ It should be free from dead knots.
~ A good timber should be durable and capable of resisting the action of fungi, insects, and chemical, physical and mechanical agencies.
~ It should be fire-resistant.
~ It should have the property of elasticity.
~ It should be hard.
~ It should be strong for working as a structural member such as a beam, rafter, purlin, etc.
(NOTE: The heavier and dark-colored timber is usually strong.)
4. Uses of Timber
~ It is generally used in the form of posts, beams, lintels, doors, window frames, roof members, piles, etc.
~ It is used for flooring, ceiling, paneling, etc.
~ It is used for the formwork, timbering for trenches, scaffolding, transmission poles, and fencing.
~ It is used in making furniture and musical instruments.
5. Parts of a Timber Tree
i) Growth of tree:
The tree sucks its food from the soil through its roots in the form of sap as moisture. The sap is raised by cells and fed to the branches and leaves of the tree. The sap consists of moisture and mineral-like Phosphates and Nitrates.
A young tree grows taller and thicker every year with a period of rapid growth each spring and slower growth in summer.
ii) Pith (Medulla):
It is the innermost central portion of the tree. It feeds the sap from roots to leaves.
It is larger in young trees than that in mature trees.
It has a dark color.
It is usually about 12.5 mm in diameter, but sometimes it is barely visible.
iii) Heart Wood:
The portion surrounding the pith is called heartwood. It is compact, strong, durable, and darker in color.
The percentage of moisture is very less in the central part. The heartwood increases with the size of the tree & age of the tree too.
The heartwood provides the best timber for engineering work and instruction.
iv) Sap Wood:
The trunk part between the heartwood and cambium is called sapwood.
It is light in weight, softer and weaker part.
It consists of high percentages of moisture.
Due to this, the wood is prone to deflect, so it is not used for commercial purposes.
v) Cambium layer:
The thin layer adjacent to the bark is known as the Cambium layer.
It is mainly responsible for the circumferential growth of the tree.
If the bark is removed from any region, the cambium layer gets exposed, and the cells cease to be active that are inactive, resulting in the death of a tree.
vi) Inner bark:
It is the inner skin of the layer covering the cambium layer from the injury.
vii) Outer bark:
It consists of wood fiber and is a stream’s outer cover or skin.
It often shows fissures and cracks.
It prevents the tree from injuries and weathering action.
viii) Medullary ray:
It is the radial ray from the pith to the cambium layer.
This ray binds the annual rings together. Also, it carries sap to various portions of the tree.
ix) Annual ring:
It is the concentric layer of wood around the pith.
Every year such a layer is added to the trunk of the tree.
The number of annual rings indicates the number of the edge of trees.
| Read Also: Seasoning of Timber |
