Timber – #Building Materials

Timber 

1. Introduction

Timber is wood obtained from mature trees and used for construction and engineering purposes after proper processing.

👉 In simple words: Timber is wood suitable for building work such as doors, windows, furniture, and roofs.

2. Core Concepts
3. Difference Between Wood and Timber

Wood	Timber
Raw material from trees	Processed wood for construction
Contains moisture	Seasoned and usable

1. Structure of a Tree

Important for understanding timber quality.

• Bark – Outer protective layer
• Cambium layer – Helps in growth
• Sapwood – Light coloured, less durable
• Heartwood – Dark coloured, strong and durable
• Pith – Central core

1. Classification of Timber
2. Based on Mode of Growth

(a) Endogenous Trees

• Grow inward
• Fibrous structure
• Examples: Bamboo, Palm

(b) Exogenous Trees

• Grow outward in rings
• Used for construction
• Examples: Teak, Sal

2. Based on Botanical Classification

(a) Softwoods

• From coniferous trees
• Light in weight
• Examples: Pine, Deodar

(b) Hardwoods

• From deciduous trees
• Strong and durable
• Examples: Teak, Sal

1. Properties of Good Timber

A good timber should have:

• High strength
• Durability
• Hardness
• Toughness
• Good appearance
• Resistance to insects

1. Seasoning of Timber

Seasoning = Process of removing moisture from timber.

Methods:

• Natural seasoning (air drying)
• Artificial seasoning (kiln drying)

Advantages:

• Increases strength
• Prevents warping
• Increases durability

1. Defects in Timber

Defect	Cause
Knots	Branch growth
Shakes	Cracks
Warping	Uneven drying
Dry rot	Fungal attack

1. Uses of Timber

• Doors and windows
• Furniture
• Roof trusses
• Railway sleepers

3. Step-by-Step Practical Examples

Example 1: Selecting Timber for Door Frames

Problem:
Which timber is suitable for door frames: Teak or Pine?

Step 1: Identify requirement

Door frames need durability and strength.

Step 2: Compare

Property	Teak	Pine
Strength	High	Medium
Durability	Very high	Low

Step 3: Final choice

➡ Teak is more suitable for door frames

Example 2: Effect of Seasoning

Question:
Why is unseasoned timber not used in construction?

Step 1: Observe property

Green timber contains moisture.

Step 2: Identify problem

Moisture causes shrinkage and warping.

Step 3: Conclusion

➡ Seasoning is necessary before use.

4. Visual Aid Description (Diagram)

Title: Structure of a Tree Trunk

A circular cross-section diagram showing:

Outer → Inner:

Bark → Cambium → Sapwood → Heartwood → Pith

Each layer labelled clearly.

This diagram helps in understanding timber quality.

5. Exam Focus: Must-Know Points ⭐

• Timber is seasoned wood suitable for construction.
• Heartwood is stronger and more durable than sapwood.
• Exogenous trees provide useful timber.
• Seasoning improves strength and durability.
• Teak is one of the best construction timbers.

6. Multiple Choice Questions (MCQs)
7. Timber is:
8. Raw wood
   B. Processed wood for construction
   C. Tree bark
   D. Green wood

Answer: B

Explanation: Timber is wood suitable for construction after processing.

2. Strongest part of tree is:
3. Bark
   B. Sapwood
   C. Heartwood
   D. Pith

Answer: C

Explanation: Heartwood is dense and durable.

3. Teak is a:
4. Softwood
   B. Hardwood
   C. Endogenous tree
   D. Fibrous plant

Answer: B

Explanation: Teak is a hardwood.

4. Pine belongs to:
5. Hardwoods
   B. Softwoods
   C. Endogenous trees
   D. Shrubs

Answer: B

Explanation: Pine is a softwood.

5. Seasoning means:
6. Cutting trees
   B. Shaping wood
   C. Removing moisture
   D. Polishing wood

Answer: C

Explanation: Seasoning removes moisture.

6. Which method is fastest for seasoning?
7. Natural seasoning
   B. Water seasoning
   C. Kiln seasoning
   D. Smoke seasoning

Answer: C

Explanation: Kiln seasoning is artificial and fast.

7. Knots are caused by:
8. Insects
   B. Branch growth
   C. Fungi
   D. Fire

Answer: B

Explanation: Knots are bases of branches.

8. Defect caused by fungal attack is:
9. Knots
   B. Shakes
   C. Dry rot
   D. Warping

Answer: C

Explanation: Dry rot is due to fungus.

9. Warping occurs due to:
10. Insects
    B. Uneven drying
    C. Fire
    D. Polishing

Answer: B

Explanation: Uneven drying causes bending.

10. Which timber is best for furniture?
11. Pine
    B. Teak
    C. Bamboo
    D. Palm

Answer: B

Explanation: Teak is strong and durable.

11. Sapwood is:
12. Strongest part
    B. Weak and light coloured
    C. Central core
    D. Outer bark

Answer: B

Explanation: Sapwood is softer and less durable.

12. Pith is located at:
13. Outside
    B. Centre
    C. Between bark and sapwood
    D. Between sapwood and heartwood

Answer: B

Explanation: Pith is the central core.

13. Bamboo is a:
14. Hardwood
    B. Softwood
    C. Endogenous tree
    D. Exogenous tree

Answer: C

Explanation: Bamboo grows inward.

14. Growth rings are seen in:
15. Endogenous trees
    B. Exogenous trees
    C. Shrubs
    D. Herbs

Answer: B

Explanation: Exogenous trees grow outward in rings.

15. Which defect is a crack in timber?
16. Knot
    B. Shake
    C. Warp
    D. Dry rot

Answer: B

Explanation: Shakes are cracks.

16. Which timber is used for railway sleepers?
17. Pine
    B. Teak
    C. Sal
    D. Bamboo

Answer: C

Explanation: Sal is strong and durable.

17. Main advantage of seasoning is:
18. Colour change
    B. Weight increase
    C. Strength increase
    D. Cost increase

Answer: C

Explanation: Seasoning improves strength.

18. Softwoods are obtained from:
19. Deciduous trees
    B. Coniferous trees
    C. Palm trees
    D. Shrubs

Answer: B

Explanation: Softwoods come from conifers.

19. Which is NOT a defect?
20. Knot
    B. Shake
    C. Seasoning
    D. Warping

Answer: C

Explanation: Seasoning is a treatment, not a defect.

20. Heartwood is preferred because it is:
21. Cheap
    B. Light
    C. Durable
    D. Easy to cut

Answer: C

Explanation: Heartwood is durable.

21. Timber used in roof trusses must be:
22. Weak
    B. Durable
    C. Soft
    D. Decorative

Answer: B

Explanation: Roof members need durability.

22. Cambium layer is responsible for:
23. Protection
    B. Strength
    C. Growth
    D. Colour

Answer: C

Explanation: Cambium causes growth.

23. Timber attacked by insects shows:
24. Knots
    B. Shakes
    C. Worm holes
    D. Warping

Answer: C

Explanation: Insects create holes.

24. Natural seasoning is also called:
25. Kiln drying
    B. Air drying
    C. Smoke drying
    D. Water drying

Answer: B

Explanation: Natural seasoning uses air.

25. Best timber for door and window frames is:
26. Pine
    B. Teak
    C. Bamboo
    D. Palm

Answer: B

Explanation: Teak is strong and durable.