Category: Timber & Industrial Timber Products

Only teak has been divided into three classes, whereas others are classified into two classes only, viz., first class and second class. 1. First-class Deodar No individual ‘hard and sound knot’ shall be more than 25 mm in diameter. The total area of live knots shall not exceed 1% of the area of the piece.…

Teakwood is classified into three grades, viz., superior, first and second depending on the defects. The classification of teak based on the permissible defects, viz., cross grain, knots, pith, pockets or streaks, sapwood, pin holes and worm holes is presented in Table 10.1. Table 10.1 Permissible defects for the classification of teak Source: IS: 4021–1967.

As per Indian Standards (IS: 4021–1967), it is preferred that timber used for building construction purposes is of one of the following four types:

The process of a cutting down or knocking down or causing trees to fall to the ground is called the felling of a tree. Trees have to be felled only when they are very close to maturity or have just matured. Generally, trees attain maturity between 50 and 100 years. Trees cut before maturity may…

A tree grows through the tops of branches. Just within the inner bark, the tree becomes thicker by the formation of cells. A young tree grows taller and thicker every year. The growth is rapid during spring and slower during late summer and early fall. In young trees, hollow cells are alive. During the growing…

A cross-section of an exogenous tree is shown in Fig. 10.1. It shows almost distinct concentric rings called annual rings. Pith is the innermost central portion consisting of cellular tissues. The inner annular area surrounding the pith is called heartwood. Heartwood is the one which is used for all engineering works. The portion between the cambium layer and the heartwood…

These trees grow outwards by the addition of rings of young wood. A cross-section of these trees shows distinct approximate concentric rings called annular rings. Timber from such trees is mainly used in engineering works. They are further classified into two types, viz., softwood and hardwood. (i) Softwood Softwoods have needle-like leaves and are also…

These trees grow by the formation of layers. In such trees new wood crosses and penetrates the fibres of the wood previously formed, e.g., bamboo, palmyrah, coconut, etc. Such trees are not useful for engineering works.

According to the manner of growth, trees may be broadly classified as Endogenous trees and Exogenous trees.

Basic Structure of a Tree A tree consists of a trunk, a crown and roots. The functions of the roots are to implant the tree in the soil, absorb moisture and mineral substances it contains and in turn supply them to the trunk. The trunk supports the crown and serves to provide water and nutrients…