---
title: "Defects of timber"
subject: "Civil Engineering Materials"
chapter: 7
key: "semester_3/civil_engineering_materials:defects-of-timber"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/defects-of-timber
site: BCT Engineering
---

# Defects of timber

Civil Engineering Materials · Chapter 7: Timber

- Asked in: 2071 Chaitra, 2 marks; 2068 Chaitra, 1 marks; 2059 Poush (old course), 3 marks; 2066 Shrawan (old course), 2 marks (asked 4 times)
- Video: [5.  Timber Defects](https://www.youtube.com/watch?v=9G67faHISI0) — VIPArts Department
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/defects-of-timber
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-7

## Question

What are the defects of timber?

## Short answer

Timber defects include knots, shakes, warping, checks, splits, honeycombing, and decay from fungi or insects. They arise from natural growth, improper seasoning, conversion faults, and biological attack, reducing strength and durability.

## Answer

Defects reduce the strength, durability and appearance of timber. They are grouped by cause.

#### 1. Defects due to natural forces (during growth)
- **Knots:** bases of branches buried in the trunk; they weaken timber and distort grain.
- **Shakes:** cracks that separate fibres along the grain: heart shake, star shake, cup shake (ring shake), and radial shake.
- **Wind cracks and upsets, rind galls, burls, twisted fibres, and water stain.**

#### 2. Defects due to seasoning
- **Warping** (bow, cup, twist, spring), **checks**, **splits**, **honeycombing**, **case hardening**, **collapse**.

#### 3. Defects due to conversion
- Chip marks, torn grain, diagonal grain, wane (rounded edge with bark).

#### 4. Defects due to fungi and insects
- **Dry rot, wet rot, blue stain,** and attack by termites, powder-post beetles and marine borers.

Note: Wood with such defects is graded lower or rejected.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which is a defect due to natural forces during growth?
   A. Honeycombing
   B. Chip marks
   C. Dry rot
   D. Knots
   Answer: D. Knots are branch bases buried in the trunk. (Key point: Growth defects)

2. Which group lists defects due to seasoning?
   A. Warping, checks, splits, honeycombing, case hardening
   B. Knots, shakes, burls
   C. Wane, chip marks, torn grain
   D. Dry rot, wet rot, blue stain
   Answer: A. Those are seasoning defects. (Key point: Seasoning defects)

3. Wane is a defect arising from
   A. Fungal attack
   B. Conversion (sawing) leaving a rounded edge with bark
   C. Growth faults
   D. Seasoning
   Answer: B. Wane is a conversion defect. (Key point: Conversion defects)

4. Dry rot and blue stain are caused by
   A. Rapid drying
   B. Poor sawing
   C. Fungi
   D. Wind
   Answer: C. They are fungal defects. (Key point: Fungal defects)

## Related in Civil Engineering Materials

- [Defects of timber by natural forces](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Atimber-defects-natural-forces) — Civil Engineering Materials, chapter 7
- [Defects caused by seasoning](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aseasoning-defects-timber) — Civil Engineering Materials, chapter 7
- [Defects during growth phase of trees](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Atimber-defects-growth-phase) — Civil Engineering Materials, chapter 7

## Related in other subjects

- [Types of timber and its defects](https://www.bctengineer.com/question.md?key=semester_6%2Fdesign_of_steel_and_timber_structure%3Atimber-types-defects) — Design of Steel and Timber Structure, chapter 9