Timber: Meaning, Defects, Types and structure

By BYJU'S Exam Prep

Updated on: September 25th, 2023

Timber is wood used for many purposes in structural engineering design. It has less strength in comparison to steel and some other materials. It can be used for the construction of buildings and houses and also for the construction of furniture. Timber is used in construction because of its advantages. Wood is a hard and fibrous substance that forms a major part of the trunk and branches of a tree.

Timber is also a natural polymeric material that does not age. Wood as a building material falls into two major classes natural and man-made. With the advances in science and technology, wood in its natural form as timber, lumber, etc., is being rapidly replaced by composite wood materials in which natural wood is just a basic ingredient of a matrix or a laminate. The latter is more useful and adaptable as they may be treated chemically, thermally or otherwise per requirements. Some examples are plywood, fibreboards, chipboards, compressed wood, impregnated wood, etc.

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What is Timber?

Wood can be classified into different types; Timber is one type of wood. It can be reformed in terms of beams and other structures. It is referred to as Lumber in some countries like US and Canada. Timber can also be referred to as the firewood of some special trees.

Timber wood can yield its minimum size in terms of dimensions. It can be used for structural purposes. Generally, timber is the only wood preferred for building use. It can also be shaped in standard sizes with the help of proper finishing for industrial purposes. Timber is provided in the GATE CE syllabus as well. It can be used for the construction of furniture and other building accessories.

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Timber Meaning

Wood timber can be defined as the wood of the growing timber. It can be used for the construction of buildings. Sometimes, it is referred to as a wood material. Timber has a variety of uses based on its suitability.

The strength of timber is different in all directions. So, it can be said that the non-homogenous material. Because of its less strength, it is generally used for temporary construction but can be used for constructing permanent structures that are required for lesser strength.

Short Notes on Timbering

Timber is a material used for the construction of buildings and other structures. Timbering is the process of using timbers to prevent the side of a trench against its collapse. In the case of the larger excavation depth, the trench side may collapse if the surrounding soils are sufficiently hard. So, timbering the trench can save the trench from its collapse.

Use of Timbering 

Timbering is generally used in the foundation of trenches. Here are a few points for the importance of timbering are listed below.

  • Timbering can be used for the safety of the workers that are doing excavation work.
  • It can also be used for the purpose of the safety of the surrounding landslide.
  • It can also be used for the purpose of the safety of public services like telephone cables, water pipes, etc.

Defects in Timber

Timber is the product of a natural material, And there can be imperfections in the natural materials. So, Timbers can have some defects; these defects cause weakness and some other difficulties in the proper functioning of the timbers. But only some of the defects are harmful to the construction; it may be useful for some specific uses of the timber.

These defects can be due to natural forces, insects, fungi, improper seasoning, or defective conversion. These defects important for the GATE exam include knots, twists, shakes, rind galls, shake etc. Knots can be either dead knots or live knots. And shakes or further classified as start shakes, ring shakes, heart shakes, etc.

Download Formulas for GATE Civil Engineering – R.C.C.

Types of Timber

Based on the different properties of timber, it can be classified into different types. Broadly it can be classified into hardwoods and softwoods.

  • Birch
  • Bamboo
  • Cherry
  • Cross-laminated
  • Glulam
  • Lime
  • Green timber

Structure of Timber

A tree can be divided into three portions, a crown composed of branches and leaves, a trunk, and roots. The trunk accounts for about 80 percent of the total bulk of the wood. The macrostructure of the timber can be studied by cutting the trunk in three directions. In the cross-sectional and radial ducts, the following main parts of a tree, e.g., bark, cambium, sapwood, heartwood, and pith, become readily apparent. Each of the components has a specific function. The bark protects the wood against mechanical damage. Its inner layer, called bast, conveys the crown’s nutrients downwards and stores them. The function of cambium is to grow wood cells on the inside and smaller bast cells on the outside. The sapwood assists in the life process of a tree by storing up starch and conducting sap. The cells in the sapwood are active. The heartwood gives firm support to the tree. With tree growth, the inner older trunk portion cells gradually become inactive and lifeless but do not decay. This portion of the trunk is called heartwood. The pith is at the center of the cross-section, a small area occupied by friable tissues consisting of thin-walled, loosely connected cells called piths. In a felled tree, it easily crumbles and rots. In the cross-sectional direction, nutrients pass from the bast to the heart through groups of cells running at right angles to the cambium layers and are referred to as medullary rays.


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