---
title: "Necessity of underpinning work"
subject: "Building Technology"
chapter: 8
key: "semester_6/building_technology:underpinning-necessity-072m"
source: https://www.bctengineer.com/q/semester_6/building_technology/underpinning-necessity-072m
site: BCT Engineering
---

# Necessity of underpinning work

Building Technology · Chapter 8: Temporary construction

- Asked in: 2072 Magh, 2 marks
- Video: [What is Underpinning? Types And Methods Explained | Underpinning Series - 1](https://www.youtube.com/watch?v=JqWlG_03zhI) — X Plan Nation
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/underpinning-necessity-072m
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-8

## Question

Describe the necessity of underpinning work.

## Short answer

Underpinning is necessary when foundations have settled or are weak due to poor soil or overload, when loads increase (e.g. extra storeys), when adjacent deep excavation or lowered water table reduces bearing capacity, or when the original foundation is faulty or damaged by roots, mining, subsidence or earthquake.

## Answer

Underpinning is needed in the following cases.

- Foundation has settled or is weak due to poor soil or an overload.
- A building is to be raised (extra storeys) and loads increase.
- Adjacent deep excavation or new basement lowers the support (e.g. neighbouring building).
- A change in water table, scouring or earthquake damage reduces bearing capacity.
- Faulty or shallow original foundation, or damage by roots, mining, or subsidence.

## Check yourself

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

1. Which situation requires underpinning?
   A. The foundation has settled or is weak due to poor soil or overload
   B. The ceiling is too high
   C. Plaster has cracked
   D. The paint is peeling
   Answer: A. Settled or weak foundations need strengthening or deepening. (Key point: Settlement)

2. Why may underpinning be needed when extra storeys are added?
   A. Because the water table drops permanently
   B. Because loads on the foundation increase
   C. Because the wall becomes thinner
   D. Because bricks shrink
   Answer: B. Extra storeys increase load beyond what the old foundation was designed for. (Key point: Added load)

3. How can a neighbouring deep excavation or basement create a need for underpinning?
   A. It increases the bearing capacity
   B. It cures the soil
   C. It lowers the support around the existing foundation
   D. It reduces the building's load
   Answer: C. Excavation next to a footing removes lateral and vertical support, so the foundation must be extended deeper. (Key point: Adjacent excavation)

## Related in Building Technology

- [Underpinning: necessity, procedure, methods](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aunderpinning-necessity-methods) — Building Technology, chapter 8, asked 3×
- [Scaffolding, underpinning, shoring; underpinning methods](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aunderpinning-scaffold-shoring-terms) — Building Technology, chapter 8