Timber MCQ Quiz - Objective Question with Answer for Timber - Download Free PDF

Explanation:

Timber:

• Timber is sawn or milled wood used for engineering purposes like building, furniture and railway track wooden sleeper construction.

Classification of the tree:

For engineering purposes, the trees are classified according to their mode of growth.

(i) Endogenous tree:

• These trees grow inwards
• Timber from these trees has very limited engineering applications.
• Example of endogenous trees are bamboo, cane, palm etc.

(ii) Exogenous tree:

• These trees grow outwards, increasing in bulk with the formation of the ring every year.
• These annual rings are used for predicting the age of the tree.
• These trees are mostly used for engineering works.
• They are further divided as conifers and deciduous.

Conifers (Evergreen trees):

• The leaves of these trees do not fall till new ones are grown. These have needle-shaped leaves and bear cone-shaped fruits.
• These trees yield softwood (easily cut), which are generally light coloured, resinous, lightweight and weak
• They have distinct annual rings.
• Example: deodar, pine, fir and larch

Deciduous or board leaf trees:

• These trees have flat broad leaves. The leaves of these trees do not fall till new ones appear in the spring season.
• They do not show distinct annual rings.
• These trees yield hardwood, which is generally close-grained, strong, heavy, dark coloured, durable and nonresinous; and are used for engineering applications.
• Example: teak, mahogany, Sheesham, oak, sal, babool etc.

Important Points

(i) Hardwoods are used in engineering construction which are derived from deciduous trees, whereas conifers trees yield softwood which is used for other purposes like making sports equipment, paper etc.

(ii) The names hardwoods and softwoods are commercially popular but have nothing to do with the hardness of the particular group some softwoods like deodar are harder than hardwoods like papita.

Explanation:

During the process of converting timber to commercial form, the defect created due to the impression of the fallen tool on the surface is called Torn grain.

Types of defects in timber are as follows:

1) The defect arises due to conversion of timber:

Chip mark, Torn grain, Diagonal grain, and wane.

2) The defect arises due to Fungi:

Heart rot, Brown rot, Dry rot, Sap stain, and Blue stain.

3) Defects arises due to Natural forces:

Cup shakes, Ring shakes, Heart shakes, Star shake, and radial shake.

4) Defects arise due to Seasoning:

Bow, warp, cup, and Twist.

Explanation:

A particle board (also known as chipboard) is made from wood chips, sawmill shavings, and other wood residues that are bonded together with a synthetic resin or binder under heat and pressure. The process involves:

1. Wood Chips and Binder: The raw materials are mixed with a resin (such as urea-formaldehyde) that acts as the binder.

2. Heat and Pressure: The mixture is then compressed and cured under heat to form a solid panel. This process ensures that the particles stick together and form a rigid board.

Additional InformationParticle board, also known as chipboard, is an engineered wood product made from wood chips, sawdust, and other wood residues that are bonded together using synthetic resins. It's commonly used in furniture, cabinetry, and as a base for veneers in many construction and interior design applications

Types of Particle Board

• Standard Particle Board: The most basic form, suitable for applications like furniture and general construction.

• Moisture-Resistant Particle Board: Treated with chemicals to resist water absorption, making it more suitable for environments where moisture is a concern (like kitchens).

• High-Density Particle Board: Offers greater strength and durability compared to standard particle board, used for applications requiring more load-bearing capacity.

Explanation:

Air seasoning is also called natural seasoning because:

• It involves drying timber naturally in the open air.

• Timber is stacked in a way that allows air to circulate around it.

• Moisture evaporates slowly, reducing the risk of cracks and warping.

Additional Information

Controlled Seasoning

• This refers to seasoning done in a controlled environment—where temperature, humidity, and airflow are monitored.

• It ensures faster and more uniform drying compared to natural methods.

• Kiln seasoning is a type of controlled seasoning.

Kiln Seasoning

• Timber is placed inside a kiln (a chamber) where heat and humidity are regulated.

• It allows quick drying in just a few days, compared to months for natural seasoning.

• Reduces chances of fungus, insects, or defects like warping and cracking.

• It’s more expensive but gives better quality timber.

Artificial Seasoning

• General term for any non-natural (non-air) seasoning method.

• Includes:

  • Kiln seasoning

  • Chemical seasoning (using salt solutions)

  • Electrical or infrared seasoning

• These methods are faster, more precise, and suitable for industrial use

Preservation of timber is the process of prevention of timber from various defects such as Fungal attack, termite attack, weather effect etc.

Felling of timber is the process of sawing of natural wood from trees.

Seasoning of timber is the process of removal of water present in natural wood.

Conversion of timber is the process of cutting of sawn wood into section used for the engineering purpose. Types of timber conversion – Ordinary sawing, Tangential sawing, Quarter sawing, Radial sawing.

The fire resistance of timber can be enhanced by phosphates of ammonia, a mixture of ammonium phosphates and ammonium sulphate, borax and boric acid, sodium arsenate etc.

Additional Information 

Coating with Tar paint - This option is not typically used to enhance fire resistance. In fact, tar paint can be combustible and may actually increase the fire risk to the timber rather than mitigating it.

Pumping creosote oil into timber under high pressure - Creosote treatment is primarily used to protect timber against rot and insect damage rather than to enhance its fire resistance. Creosote can be combustible, and its primary purpose is not to make timber fire-resistant.

Seasoning process - Seasoning, or drying the timber, is vital for reducing its moisture content, which can indirectly affect its combustibility. However, the primary purpose of seasoning is not to enhance fire resistance but to improve the timber's strength, stability, and resistance to decay. While dry wood can catch fire more easily than wet wood, seasoning in itself is not a method for making timber fire-resistant.

Concept:

The classification of timber as per IS: 399 is as follows:

Concept

Dry rot: It is the decomposition of felled timber caused by the action of various fungi. The fungus reduces fibers to a fine powder and the timber loses its strength. This disease is highly infectious and causes tremendous destruction.

It occurs when the timber is imperfectly seasoned and placed in a moist, warm confined atmosphere having no free access to air.

Fungus rapidly dies when exposed to air or sunlight. The best remedy is to cut away the affected part and paint the remaining part.

Upset: This defect occurs when timber is subjected to crushing or compression due to natural force.

Wet rot: This decomposition of sap occurs when timber is subjected to alternate wet and drying condition.

Foxiness: This defect appear in the form of discolouring due to overmaturity of tree.

Note: 

Fungi that attack growing trees and continue to damage it in structures are known white or brown rot, white trunk rot, etc.

Explanation:

As per IS 287: 1993, Clause 3

The country has been broadly divided into the following four zones on the basis of information collected by the Forest Research Institute on the seasonal changes in the moisture content of timber at 12 localities in India, supplemented by published meteorological data on the humidity variations in the country.

1. Zone I Average annual relative humidity less than 40 percent.
2. Zone II Average annual relative humidity 40-50 percent.
3. Zone III Average annual relative humidity above 50 and up to 67 percent.
4. Zone IV Average annual relative humidity is more than 67 percent.

Defects due to conversion

1) chip mark

2) Diagonal grain

3) Torn grain

4) wane

Defects due to Insect

1) Marine Borers

2) Beetles

3) Termites

Defect due to Fungi

1) Blue Rot

2) Heart Rot

3) Dry Rot

4) Sap stain

5) Wet Rot

Defect due to seasoning

1) Bow

2) check

3) collapse

4) cup

5) Twist

6) Split

7) Warp

Defects due to natural forces

1) knots

2) Burb

3) Ring galls

4) Twisted fiber

5) shaker

Concept:

1. Pith : It is the inner most part of tree consist of cellular tissue which is used for nourishment of tree in young age.

2. Sapwood : It is outer annual rings between heartwood and cambium layers. It is the living, outermost portion of a woody stem or branch.

3. Heartwood : The inner annual rings surrounding the pith is known as heartwood. It imparts rigidity to the tree.

4. Cambium Layer : It is a thin layer of sap between sapwood and inner bark.

5. Inner bark : It gives protection of the cambium layer

6. Outer bark : It is the outermost part of the tree

Explanation

Following are various forms in which the timber is available in the market:

(1) Batten: This is a timber piece whose breadth and thickness do not exceed 50 mm.

(2) Baulk: It is a roughly squared timber piece and it is obtained by removing bark and sapwood. One of the cross-sectional dimension exceeds 50 mm, while the other exceeds 200 mm.

(3) Board: It is a plank i.e. a timber piece with parallel sides. Its thickness is less than 50 mm and its width exceeds 150 mm.

(4) Deal: It is a piece of softwood with parallel sides. Its thickness varies from 50 mm to 100 mm and its width does not exceed 230 mm.

(5) End: This is a short piece of the batten, deal, scantling, etc.

(6) Log: It is the trunk of the tree obtained after the removal of branches.

(7) Plank: It is a timber piece with parallel sides. Its thickness is less than 50 mm and its width exceeds 50 mm.

(8) Pole: It is a sound long log of wood. Its diameter does not exceed 200 mm. It is also known as a spar.

(9) Quartering: It is a square piece of timber, the length of a side being 50 mm to 150 mm.

(10) Scantling: This is a timber piece whose breadth and thickness exceed 50 mm, but are less than 200 mm in length. These are the pieces of miscellaneous sizes of timber sawn out of a log.

Explanation:

Preservation of timber:

Preservation of timber is done with the help of different types of preservatives to increases the life of the timer, make the timer structure durable, and protect it from the attack of fungi & insects.

Different types of preservative:

ASCU Treatment:

• This is a special type of preservative which is developed at Forest research institute Dehradun.
• Which composition is as follows;

1. As₂O₅.2H₂O (Arsenic pentaoxide)
2. CuSO₄.5H₂0 (Copper sulfate)
3. K₂Cr₂O₇ (Potassium dichromate)
4. Na₂Cr₂O₇.2H₂O (Sodium dichromate)

• ​This preservative gives protection against the attack of White ants.

​Coal Tar:

• The process of heating the coal tar to make it workable condition is known as Tarring.
• Coal tar is Fire resistant.

Creosote oil:

• Creosote oil is one of the best antiseptics.
• It is derived from wood or coal.
• It is harmless to wood and inflammable.

Oil paints:

• The timber surface is coated with oil paints.
• it makes the timber durable.​​

IS: 1141-1958 – Classification of timber for seasoning of timber

IS: 1708-1969 – Methods of testing of small clear specimens of timber

IS : 4970-1973 – key identification of commercial timber

IS : 399-1963 – Classification of commercial timbers and their zonal distribution

Note:

Some important IS codes are following

IS: 456-2000 – Plain reinforced concrete

IS: 800-2007 – General construction of steel

IS: 1343- 1980 – code for practice for prestressed

IS: 383- 1970 – Coarse and fine aggregate for concrete-specification

IS: 875- 1987 – Practice for the design of dead load (Part 1) , live load (Part 2) , wind load (Part 3) , snow load (Part 4) , special load & load combination (Part 5)

IS: 1893- 2002 – Earthquake resistance design of structure

IS 10262- 2009 – Guidelines for concrete mix design proportioning

IS: 269 –Specification for 33, 43 and 53 grade OPC

Explanation:

Sawing:

Sawing is the cutting of timber from logs into different shapes and sizes. Sawn timber is generally cut into varying rectangular widths and lengths, but may also be wedge-shaped. Common sawn timber products include solid timber beams and more rectangular timber sections.

Methods of Sawing Timber:

Rift or radial sawing:

• Timber cut parallel to medullar rays and perpendicular to annual rings.
• Adopted for strong timber pieces
• Least shrinkage but mostly wasted.
• Greater decorative effect.

Ordinary Sawn or Through Sawing:

• Parallel cuts made throughout the length of the log.
• Cutting parallel slices of planks.
• Easiest and economical method.
• Shrinkage of sapwood more than the heartwood.
• Causing warp and twisting of planks.

Quarter Sawing:

• A tendency to cup i.e. to curve in a transverse direction.
• This method is applied to wood, not having distinct medullar rays.
• This method produces very fine wood.

Tangential Sawing:

• The sawing is at right angles to medullary rays.
• Boards or planks are sawn tangentially to annual rings
• Not suitable for flooring