--- title: "What is retrofitting; why it is necessary" subject: "Building Technology" chapter: 11 key: "semester_6/building_technology:retrofit-why-necessary" source: https://www.bctengineer.com/q/semester_6/building_technology/retrofit-why-necessary site: BCT Engineering --- # What is retrofitting; why it is necessary Building Technology · Chapter 11: Earthquake protection & Retrofitting in building - Asked in: 2071 Magh, 4+4 marks - 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-why-necessary - Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-11 ## Question What is retrofitting of a building? Why is it necessary? ## Short answer Retrofitting is strengthening an existing building to improve its seismic resistance beyond the original design. It is necessary because many older buildings lack seismic design, codes are updated, use changes or deterioration reduces capacity, and it saves lives at a fraction (10–30%) of reconstruction cost. ## Answer #### 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. It is done after a **structural assessment** (condition survey, NDT, calculation of the capacity versus demand) that identifies weak points. The common methods are jacketing, adding shear walls/bracing, strengthening of connections and foundation, wall plastering with mesh, and use of FRP. #### Why it is necessary - 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. What is retrofitting? A. Demolishing and rebuilding the building B. Strengthening an existing building to resist earthquake forces better than originally designed C. Restoring a building exactly to its old strength D. Painting and plastering the walls Answer: B. Retrofitting upgrades the strength, stiffness, ductility and load path of an existing structure. (Key point: Definition) 2. What must be done before retrofitting? A. Immediate jacketing of all columns B. Adding extra floors C. Structural assessment (condition survey, NDT, capacity vs demand) to find weak points D. Applying FRP without testing Answer: C. Assessment identifies weak points so that the right method is chosen. (Key point: First step) 3. Compared with demolition and reconstruction, retrofitting typically costs: A. About 10-30% of new construction cost B. More than new construction C. About 100% of new construction D. Less than 1% of new construction Answer: A. Retrofitting is much cheaper than rebuilding, typically 10-30% of new cost. (Key point: Cost) 4. Which is a reason retrofitting becomes necessary? A. Buildings get stronger with age B. Rain water improves masonry C. Added floors increase capacity D. Codes are revised, so buildings made to old codes become deficient Answer: D. Code revision, change of use, added floors, deterioration and past damage all create deficiencies. (Key point: Reasons) ## 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 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 - [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 and jacketing](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aretrofit-jacketing) — Building Technology, chapter 11, asked 2× - [Why joints are necessary; expansion joint](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Ajoints-why-expansion) — Building Technology, chapter 10, asked 2× ## Related in other subjects - [Value of a 20-year-old building](https://www.bctengineer.com/question.md?key=semester_8%2Fconstruction_management%3Avalue-building-20-years-2075) — Construction Management, chapter 13, asked 2× - [Value of a 10-year-old building](https://www.bctengineer.com/question.md?key=semester_8%2Fconstruction_management%3Avalue-building-10-years-2071) — Construction Management, chapter 13, asked 2× - [BoQ for IOE ICT building six labs](https://www.bctengineer.com/question.md?key=semester_8%2Finternet_and_intranet%3Aboq-ioe-ict-six-labs) — Internet and Intranet, chapter 5 - [Two-room building: brick plinth, door shutters, plaster](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Abuilding-m-two-room-three-items) — Estimating and Costing, chapter 6