Timber:

 

Timber

The word timber is derived from ‘Timbrian’ which means to build. Timber thus denotes wood which is suitable for building construction, carpeting or other engineering purposes. When it forms part of a living tree it is called ‘Standing timber’, when felled it is known as ‘Rough timber’ and when cut in to different forms such as planks, beams etc., it is known as ‘Converted timber’.

 

                  

Timbers in Stock

Properties of timber

1.      Strength: A good timber should have high strength in bending, shear and direct effects so that it can be used as a structural member such as beam or column.

2.      Appearance: A good timber possesses fine and even texture, close grains and shining dark appearance.

3.      Durability: A good timber should be durable and capable of resisting the actions of fungi, insects, chemicals and physical agencies.

4.      Hardness and Toughness: A good timber will be hard and capable of resisting shock loads.

5.      Seasoning: Seasoning is the process of removal of water from the freshly cut timber when is present in the form of sap and moisture.  A good timber is to be well seasoned before using it for any engineering purposes.

6.      Resistance to fire and thermal expansion: A good timber should have high resistance to fire.  Timber has very low coefficient of thermal expansion parallel to grains and is a bad conductor of heat.

7.      Workability: A good timber should be easily workable and should not clog the saw and can be planed easily.

8.      Defects: A good timber should be free from serious defects like knots, flaws, shakes etc.

          

Uses of Timber:

1.      For making doors, windows and ventilators.

2.      Used as flooring and roofing material.

3.      Used for making furniture.

4.      Used in making agricultural implements.

5.      Used in the manufacture of sport goods, musical instruments etc.

6.      Used in making railway coaches, wagons, buses, boats etc.

7.      Used in making sleepers for railways, fencing poles, electric poles, footways, bridge floors, temporary bridges etc.

8.       Soft wood is used for manufacture of paper, card-boards, walls paper etc.

Artificial wood- manufactured boards

Plywood

Plywood is produced by gluing together three to seven veneers that have been peeled from logs. The grain Of each successive veneer is angled at 90° from the previous one, resulting in a board that has considerable Strength and rigidity in all directions. Waterproof glue is most commonly used, giving a product that is highly resistant to moisture. Waterproof glue panels should always be chosen for farm buildings. As the wood itself. Is not waterproof, the panels are still subject to swelling and shrinkage from moisture changes.

Grades of plywood

Plywood is generally given four to five grades, based on the appearance of the surface veneers. Each panel. Has a double-letter grade to indicate the grade of the face of the panel and the back of the panel. The top-grade surface is generally free enough from defects to be finished naturally, while the second-best grade is good for painting. Lower grades are used for structural applications where appearance is of little importance. Theoretically, between 10 and 15 different grade combinations are possible. In practice, only a few tend to be available from timber merchants.

Sizes of plywood panel

As an example of a standard used in the region, the Kenya Bureau of Standards provides a standard with12 panel sizes and 9 different thicknesses. Combining grades, panel sizes and thicknesses, there are numerous permutations, but only a few will be manufactured. The most common panel size is 2 400 by 1 200 mm, in thicknesses of 9 mm, 12 mm, 15 mm and 19 mm.

Laminated boards

Laminated boards are made of strips of wood between 8 mm and 25 mm wide, glued together and covered with one or more veneers on each side. At least one pair of corresponding veneers will have the grain at right angles to the grain of the core. If the finish grain is to run parallel with the core, there must be at least two veneers per side. The same 12 panel sizes listed for plywood are also listed for blackboard. However, the thicknesses are greater, ranging from 15 mm to 50 mm, in 5 mm increments.

Particleboard

The Chips are bonded with thermosetting synthetic resins. Depending on the size of the particles, these boards are variously known as particleboard, chipboard or wafer board. Strength and rigidity generally increase with density, but that alone is not a measure of quality, as moisture resistance varies considerably and most particleboards should not be used in moist locations. Soft boards are made from uncompressed woodchips or sugarcane fibres mixed with water and glue or resins, giving a density of less than 350 kg/m³. They are inexpensive and can be used for wall or ceiling surfaces that are not subject to high-moisture conditions.