---
title: "Techniques of retrofitting a building"
subject: "Building Technology"
chapter: 11
key: "semester_6/building_technology:retrofit-techniques"
source: https://www.bctengineer.com/q/semester_6/building_technology/retrofit-techniques
site: BCT Engineering
---

# Techniques of retrofitting a building

Building Technology · Chapter 11: Earthquake protection & Retrofitting in building

- Asked in: 2078 Baisakh, 4 marks; 2075 Bhadra, 6 marks; 2070 Magh (asked 3 times)
- Video: [Method of Retrofitting (Part1)](https://www.youtube.com/watch?v=XD32mIH0NDs) — Time Line Construction
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/retrofit-techniques
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-11

## Question

Explain the techniques of retrofitting (seismic retrofitting) of a building.

## Short answer

Techniques: epoxy injection for cracks; RCC, steel or FRP jacketing of beams and columns; adding shear walls or steel bracing; foundation widening; ferrocement plaster with cross-ties; inserting lintel, sill and roof bands; RC topping for rigid diaphragm; and removing heavy parapets.

## Answer

**Retrofitting** is the strengthening or modification of an existing building so that it can resist earthquake forces better than it was originally designed to. It improves strength, stiffness, ductility and load path of the existing structure without rebuilding it.

#### Techniques of seismic retrofitting
#### 1. Local repair (member-level)
Fill cracks by epoxy or cement grout injection, replace crushed concrete or broken bricks, and replace corroded bars.

#### 2. Jacketing of members
- **RCC jacket:** extra concrete (min. 75-100 mm) with new longitudinal bars and closely spaced ties is cast around a column or beam.
- **Steel jacket:** steel plates or angles with battens are wrapped around the member and the gap is grouted.
- **FRP wrapping:** carbon or glass fibre sheets are bonded to give confinement.

#### 3. Adding shear walls or bracing
New RC shear walls, infill walls or steel X-bracing are added in frames to increase lateral stiffness and strength.

#### 4. Strengthening of foundation
Widening of footings, adding tie beams or underpinning if foundation is weak.

#### 5. Strengthening of masonry
Ferrocement or wire mesh plastering on both faces, tying with cross-links; inserting RC bands at plinth, lintel and roof levels; vertical bars at corners and jambs; grouting of cracks; stitching of cracks.

#### 6. Improving connections and diaphragm
Anchoring roof/floor to walls, tying walls with steel straps, converting flexible floors to rigid diaphragms by an RC topping.

#### 7. Base isolation and energy dissipation
Isolators or dampers are placed to reduce earthquake force transfer (costly; used for important buildings).

#### 8. Reducing weight or irregularity
Removing heavy parapets, water tanks, or upper storeys; adding walls to remove soft storey.

**Choice of technique** depends on the type of building (masonry or RCC), condition survey results (visual and NDT), the expected earthquake level, cost, and working conditions (occupied building or not).

## Check yourself

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

1. FRP wrapping gives:
   A. Weight
   B. Confinement
   C. Foundation
   D. Insulation
   Answer: B. Fibre sheets bonded around member. (Key point: FRP wrapping)

2. New shear walls or X-bracing increase:
   A. Cracks
   B. Dead load only
   C. Lateral stiffness and strength
   D. Openings
   Answer: C. They resist lateral force. (Key point: Shear walls)

3. Choice of technique depends on:
   A. Only age
   B. Colour
   C. Only height
   D. Building type, condition survey, earthquake level, cost, occupancy
   Answer: D. Several factors. (Key point: Choice of technique)

## Related in Building Technology

- [Retrofitting techniques; why it is important](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aretrofit-techniques-importance) — Building Technology, chapter 11, asked 3×
- [Retrofitting a brick masonry building](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aretrofit-brick-masonry) — Building Technology, chapter 11
- [Retrofitting and jacketing](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aretrofit-jacketing) — Building Technology, chapter 11, asked 2×
- [Retrofitting need; repairing cracks of different width](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aretrofit-repair-crack-width) — Building Technology, chapter 10
- [What is retrofitting; why it is necessary](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aretrofit-why-necessary) — Building Technology, chapter 11
- [Configuration factors for seismic safety](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aconfig-factors-seismic) — Building Technology, chapter 11, asked 2×

## Related in other subjects

- [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 base shear of a masonry building](https://www.bctengineer.com/question.md?key=semester_5%2Fdesign_of_timber_and_masonry_structures%3Abase-shear-two-storey-masonry-building) — Design of Timber and Masonry Structures, chapter 7