---
title: "Foundation classification and problems"
subject: "Building Technology"
chapter: 2
key: "semester_6/building_technology:foundation-class-problems"
source: https://www.bctengineer.com/q/semester_6/building_technology/foundation-class-problems
site: BCT Engineering
---

# Foundation classification and problems

Building Technology · Chapter 2: Foundations

- Asked in: 2070 Chaitra (old course), 4+4 marks; 2068 Baisakh (old course), 4+4 marks (asked 2 times)
- Video: [Everything About Foundation || Most important for every interview ||By- Akash Pandey||](https://www.youtube.com/watch?v=QZ-Dsu21ElE) — Unique Civil Academy 
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/foundation-class-problems
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-2

## Question

What are the general classifications of foundation? What are the common problems of existing foundation?

## Short answer

Foundations are classified as shallow (spread, strip, raft, etc.) when depth ≤ width, or deep (piles, piers, caissons) when deeper. Common problems are differential settlement, dampness, cracks, deterioration, soil movement, overloading, adjacent work effects, and earthquake damage.

## Answer

#### Classification of foundations
**Foundation** is the lowest part of the structure which transfers the load to the ground. They are classified into two main groups.

**1. Shallow foundations** (depth $D_f \le$ width $B$, or less than about 3 m)
- Spread (isolated) footing, wall (strip) footing, combined footing, strap (cantilever) footing, raft (mat) foundation, grillage footing, stepped footing.

**2. Deep foundations** (depth greater than width)
- Pile foundation (bearing, friction, bored, driven), pier foundation, well (caisson) foundation, drilled shaft.

```text
 Shallow: strip   [|____|]     Deep: pile   | | |
 ground ====================     weak soil  | | |
                                hard stratum  ===
```

#### Common problems of existing foundations
1. **Differential settlement** causing cracks and tilting, as the soil is unequal or the load is increased.
2. **Dampness** due to capillary rise through walls where DPC is poor.
3. **Cracks and deterioration** of concrete, masonry and steel through sulphate attack, corrosion and weathering.
4. **Soil movement**: Swelling and shrinking of clay, erosion, scour.
5. **Overloading** by additional floors or change of use.
6. **Effect of adjacent excavation, vibration, and water table change**.
7. **Earthquake damage and liquefaction**.

**Remedies:** underpinning, grouting, soil stabilisation, drainage, widening of footing, and jacketing.

## Check yourself

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

1. Which is a shallow foundation?
   A. Pile foundation
   B. Well foundation
   C. Pier foundation
   D. Raft (mat) foundation
   Answer: D. Raft, strip, spread and combined footings are shallow. (Key point: Shallow foundation)

2. In deep foundations the depth compared with width is
   A. Greater than the width
   B. Less than the width
   C. Equal to zero
   D. Always under 1 m
   Answer: A. Deep foundations have depth greater than width. (Key point: Deep foundation)

3. What causes differential settlement?
   A. Uniform soil only
   B. Dry weather only
   C. Painting
   D. Unequal soil or increased load
   Answer: D. Unequal soil or load gives differential settlement, causing cracks and tilting. (Key point: Differential settlement)

## Related in Building Technology

- [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×

## Related in other subjects

- [Case study: new system vs existing (cost, manpower)](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Acs-cost-manpower-automation) — Instrumentation II, chapter 10, asked 4×