---
title: "Typical damage patterns in masonry buildings"
subject: "Design of Timber and Masonry Structures"
chapter: 6
key: "semester_5/design_of_timber_and_masonry_structures:damage-patterns-masonry-lateral-loads"
source: https://www.bctengineer.com/q/semester_5/design_of_timber_and_masonry_structures/damage-patterns-masonry-lateral-loads
site: BCT Engineering
---

# Typical damage patterns in masonry buildings

Design of Timber and Masonry Structures · Chapter 6: Masonry Structures Under Lateral Loads

- Asked in: year not given, 6 marks
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/design_of_timber_and_masonry_structures/damage-patterns-masonry-lateral-loads
- Whole chapter: https://www.bctengineer.com/md/semester_5/design_of_timber_and_masonry_structures/chapter-6

## Question

Describe with sketches the typical damage patterns observed in masonry buildings due to earthquake loads. State the cause of each pattern.

## Short answer

Earthquake damage patterns: diagonal X-cracks from in-plane shear, cracks at openings from stress concentration, vertical corner cracks from out-of-phase vibration, out-of-plane bulging/overturning from bending, and delamination of leaves in multi-leaf walls.

## Answer

Masonry is brittle, weak in tension and heavy, so damage is typically cracking, separation and collapse in recognisable patterns.

#### 1. Diagonal X-cracks in piers and walls (in-plane shear)
Caused by in-plane shear when the principal tensile stress exceeds the masonry tensile strength. Cracks reverse with cyclic motion and form an X.

```text
 +-------+
 |\     /|
 | \   / |      X-cracks in
 |  \ /  |      pier or wall
 |  / \  |
 | /   \ |
 |/     \|
 +-------+
```

#### 2. Cracks at openings
Stress concentration at the corners of doors and windows leads to diagonal cracks starting at the opening corners, and horizontal cracks at sill and lintel levels; narrow piers between openings fail first.

#### 3. Vertical cracks at wall corners and junctions
Orthogonal walls vibrate out of phase, so the corner or T-junction separates (vertical crack). It is worse if there is no bonding or bands.

#### 4. Out-of-plane bulging, overturning and collapse
Long, tall or thin walls bend outward; horizontal cracks at mid-height or at floor level result, and the wall falls out. Gable walls and parapets overturn because they are not restrained at the top.

#### 5. Delamination of wall leaves and collapse of stone walls
In rubble masonry the outer leaves separate from the loose core, and the wall sheds as a pile of stones.

#### 6. Roof and floor damage
Heavy roofs on weak walls cause collapse; timber joists pull out of walls because of poor anchorage.

#### 7. Damage due to irregular plan and torsion
Irregular plans (L, T shapes), unsymmetrical openings or stiff walls on one side lead to torsion and concentrated damage at re-entrant corners.

| Pattern | Main cause | Prevention |
|---|---|---|
| X-cracks | In-plane shear | Bands, adequate wall length, reinforcement |
| Corner cracks | Poor connection | Corner stitching, bonded joints |
| Bulging, overturn | Out-of-plane bending | Small $h/t$, cross-walls, bands |
| Delamination | Weak core | Through stones, grouting |

## Check yourself

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

1. What causes diagonal X-cracks in piers and walls?
   A. Out-of-plane bending
   B. Settlement of foundations
   C. Poor roof anchorage
   D. In-plane shear when principal tensile stress exceeds masonry tensile strength, reversing with cyclic motion
   Answer: D. Cyclic in-plane shear gives principal tension beyond the strength, forming crossed diagonal cracks. (Key point: X-cracks)

2. Why do vertical cracks appear at wall corners and T-junctions?
   A. Orthogonal walls vibrate out of phase and separate, worse without bonding or bands
   B. Walls crush under vertical load
   C. Mortar shrinks
   D. Openings are too large
   Answer: A. Walls in two directions move differently, so the junction separates where the connection is poor. (Key point: Corner cracks)

3. Why do narrow piers between openings fail first?
   A. They are heavier than other walls
   B. Stress concentrates at opening corners and narrow piers have little shear capacity
   C. They have more vertical load
   D. They lack foundation
   Answer: B. Stress concentration at opening corners starts diagonal cracks, and narrow piers are the weakest links. (Key point: Cracks at openings)

4. Why do gable walls and parapets overturn?
   A. They are in-plane shear walls
   B. They are made of stronger brick
   C. They are not restrained at the top
   D. They carry no mass
   Answer: C. With no top support they act as free cantilevers and fall out under out-of-plane shaking. (Key point: Gable and parapet damage)

## Related in Design of Timber and Masonry Structures

- [Seismic design principles for masonry buildings](https://www.bctengineer.com/question.md?key=semester_5%2Fdesign_of_timber_and_masonry_structures%3Aseismic-design-principles-masonry) — Design of Timber and Masonry Structures, chapter 7
- [Seismic strengthening techniques for masonry buildings](https://www.bctengineer.com/question.md?key=semester_5%2Fdesign_of_timber_and_masonry_structures%3Astrengthening-retrofitting-masonry-buildings) — Design of Timber and Masonry Structures, chapter 7
- [Seismic bands and vertical reinforcement in masonry](https://www.bctengineer.com/question.md?key=semester_5%2Fdesign_of_timber_and_masonry_structures%3Aseismic-bands-and-vertical-reinforcement) — Design of Timber and Masonry Structures, chapter 7
- [Seismic behaviour of unreinforced and reinforced masonry](https://www.bctengineer.com/question.md?key=semester_5%2Fdesign_of_timber_and_masonry_structures%3Aseismic-behavior-urm-versus-reinforced) — Design of Timber and Masonry Structures, chapter 7
- [Permissible compressive stress of masonry as per IS 1905](https://www.bctengineer.com/question.md?key=semester_5%2Fdesign_of_timber_and_masonry_structures%3Amasonry-permissible-stress-factors-code) — Design of Timber and Masonry Structures, chapter 5
- [Masonry pier under axial load and in-plane moment](https://www.bctengineer.com/question.md?key=semester_5%2Fdesign_of_timber_and_masonry_structures%3Amasonry-pier-axial-moment-check) — Design of Timber and Masonry Structures, chapter 7

## Related in other subjects

- [Typical damage in masonry under lateral loads](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Atypical-damage-lateral-loads) — Concrete Technology and Masonry Structure, chapter 9, asked 2×
- [Pattern vs framework; GRASP patterns](https://www.bctengineer.com/question.md?key=semester_6%2Fobject_oriented_analysis_and_design%3Apattern-vs-framework-grasp) — Object Oriented Analysis and Design, chapter 3
- [Elements resisting lateral loads in masonry](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Alateral-load-resisting-elements) — Concrete Technology and Masonry Structure, chapter 9, asked 6×
- [Making brick masonry earthquake resistant](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aeq-brick-masonry) — Building Technology, chapter 11