---
title: "Causes of cracks in a building"
subject: "Building Technology"
chapter: 10
key: "semester_6/building_technology:causes-of-cracks"
source: https://www.bctengineer.com/q/semester_6/building_technology/causes-of-cracks
site: BCT Engineering
---

# Causes of cracks in a building

Building Technology · Chapter 10: Causes and prevention of cracks in buildings

- Asked in: 2074 Bhadra, 4 marks; 2072 Asoj, 4 marks; 2071 Magh, 8 marks (asked 3 times)
- Video: [Why Do Buildings Crack? | The Real Reasons Behind Cracks in Walls](https://www.youtube.com/watch?v=bzk4REp0zgY) — NOVARA Build & Design
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/causes-of-cracks
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-10

## Question

What are the main causes of cracks in a building?

## Short answer

Main causes: moisture movement (shrinkage/expansion), thermal expansion, differential foundation settlement, elastic deformation from overload, reinforcement corrosion, chemical attack (sulphate, alkali-aggregate), vegetation roots, earthquake, wind, poor workmanship, overloading, design errors, fire.

## Answer

A **crack** is a visible separation in a wall, slab, plaster or any other building element. Cracks can be structural or non-structural. The main causes are as follows.

| Cause | How it cracks the building |
|---|---|
| **Moisture movement** | Bricks, blocks and concrete expand on wetting and shrink on drying; mortar and plaster shrinkage |
| **Thermal movement** | Expansion and contraction with temperature in roofs, long walls, parapets |
| **Settlement of foundation** | Unequal settlement due to poor or non-uniform soil, wrong foundation level, change in moisture, or inadequate depth |
| **Elastic deformation** | Overload, deflection of beams and slabs, bending and shear |
| **Corrosion of reinforcement** | Rust expands and splits the concrete cover |
| **Chemical action** | Sulphate attack, alkali-aggregate reaction, carbonation |
| **Vegetation** | Roots of trees near walls and foundations |
| **Earthquake and wind** | Lateral forces on weak walls and joints |
| **Poor workmanship and materials** | Poor curing, mix, bonding, early removal of formwork, missing joints |
| **Overloading and design error** | Excess load, wrong detailing |
| **Fire, vibration** | Heat damage, machine vibration |

#### Prevention
- Investigate the soil properly and design the foundation for uniform settlement.
- Provide expansion, contraction and construction joints.
- Use good materials and a proper mortar mix; cure for at least 7 days.
- Provide plinth, lintel and roof bands.
- Protect reinforcement with enough cover.
- Remove vegetation near the foundation.
- Waterproof the roof and walls.

## Check yourself

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

1. Moisture movement causes cracks because:
   A. Bricks expand on wetting and shrink on drying
   B. Water dissolves the steel
   C. Bricks gain strength when wet
   D. Water freezes in all walls
   Answer: A. Cyclic wetting and drying changes size of bricks, blocks and concrete. (Key point: Moisture movement)

2. Which condition leads to cracks by foundation settlement?
   A. Uniform soil and equal footing depth
   B. Unequal settlement from non-uniform soil or inadequate depth
   C. Use of expansion joints
   D. Good curing
   Answer: B. Differential settlement distorts the structure and cracks it. (Key point: Foundation settlement)

3. Which is a chemical cause of cracks?
   A. Early removal of formwork
   B. Root growth
   C. Sulphate attack
   D. Thermal expansion
   Answer: C. Sulphate attack, alkali-aggregate reaction and carbonation are chemical causes. (Key point: Chemical action)

4. Which measure helps prevent cracking?
   A. Using minimum cover to steel
   B. Removing lintel bands
   C. Planting trees close to the foundation
   D. Curing at least 7 days and providing joints
   Answer: D. Good curing, joints, bands, cover and vegetation removal prevent cracks. (Key point: Prevention)

## Related in Building Technology

- [Causes and remedies of cracks](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Acracks-causes-remedial) — Building Technology, chapter 10, asked 2×
- [Painting on masonry; causes and remedies of cracks](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Apainting-masonry-cracks) — Building Technology, chapter 9
- [Structural vs non-structural cracks and causes](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Acracks-struct-nonstruct-causes) — Building Technology, chapter 10
- [Structural and non-structural cracks](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Acracks-structural-nonstructural) — Building Technology, chapter 10, asked 4×
- [Methods of repairing cracks](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Acrack-repair-methods) — Building Technology, chapter 10, asked 3×
- [Reasons for cracks in plastering](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aplaster-crack-reasons) — Building Technology, chapter 9

## Related in other subjects

- [Service connection from main pipe to building](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Aservice-connection-layout) — Water Supply Engineering, chapter 7, asked 2×
- [Building with verandah: excavation, panelled shutter, brick](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Abuilding-n-fig3-three-items) — Estimating and Costing, chapter 6
- [I-section purlin for industrial building](https://www.bctengineer.com/question.md?key=semester_6%2Fdesign_of_steel_and_timber_structure%3Apurlin-i-section-industrial) — Design of Steel and Timber Structure, chapter 8