--- title: "Retrofitting techniques; why it is important" subject: "Building Technology" chapter: 11 key: "semester_6/building_technology:retrofit-techniques-importance" source: https://www.bctengineer.com/q/semester_6/building_technology/retrofit-techniques-importance site: BCT Engineering --- # Retrofitting techniques; why it is important Building Technology · Chapter 11: Earthquake protection & Retrofitting in building - Asked in: 2079 Chaitra, 5 marks; 2077 Chaitra, 4+2 marks; 2074 Bhadra, 8 marks (asked 3 times) - Video: [What is Retrofitting Technique ? Uses of Retrofitting - Types of Retrofitting](https://www.youtube.com/watch?v=46YGCwCaySA) — REINFORCE - 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-importance - Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-11 ## Question Explain the various techniques of retrofitting in a building. Why is retrofitting in existing buildings important? ## Short answer Retrofitting includes crack injection, column/beam jacketing (RCC, steel, FRP), adding shear walls, foundation widening, masonry strengthening with ferrocement and bands, and improving connections. It is crucial because older buildings lack seismic design; retrofitting prevents collapse at a fraction of rebuilding cost and addresses code updates, deterioration or change of use. ## Answer #### Techniques of retrofitting **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. #### 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. #### Importance of retrofitting - Many older buildings in Nepal were built without engineering design or seismic code (NBC 105), so they can collapse in a moderate earthquake (as in Gorkha 2015). - Retrofitting saves lives and property at a cost much lower than demolition and reconstruction (typically 10-30% of new construction cost). - Seismic codes are revised; buildings built to old codes become deficient. - Change of use, added floors, or deterioration (corrosion, cracks, aging) reduces capacity. - Heritage and important buildings (hospitals, schools, temples) must be preserved. - Damage from a past earthquake must be repaired and the building made safe against the next one. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Retrofitting is: A. Building a new house B. Strengthening an existing building so it resists earthquakes better C. Painting D. Demolition Answer: B. It improves strength, stiffness, ductility and load path without rebuilding. (Key point: Definition) 2. A RCC jacket is typically: A. Steel only B. 5 mm paint C. 75-100 mm extra concrete with new bars and closely spaced ties D. A plaster coat Answer: C. Added around column or beam. (Key point: RCC jacket) 3. Retrofitting typically costs: A. More than new construction B. Nothing C. 100% of new D. 10-30% of new construction cost Answer: D. It is far cheaper than demolition and rebuilding. (Key point: Cost) 4. Masonry buildings are strengthened by: A. Wire mesh plastering and RC bands B. Removing bands C. Adding heavy tanks D. Removing walls Answer: A. Also vertical bars and grouting. (Key point: Masonry strengthening) ## Related in Building Technology - [Techniques of retrofitting a building](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aretrofit-techniques) — 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× - [Common problems of existing foundations](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aproblems-existing-foundation) — Building Technology, chapter 2, 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 ## 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 - [Design network for two buildings with fiber](https://www.bctengineer.com/question.md?key=semester_8%2Finternet_and_intranet%3Anetwork-design-guidelines-two-buildings) — Internet and Intranet, chapter 5