---
title: "Deep foundation types and use of shallow foundations"
subject: "Building Technology"
chapter: 2
key: "semester_6/building_technology:deep-shallow-types-079a"
source: https://www.bctengineer.com/q/semester_6/building_technology/deep-shallow-types-079a
site: BCT Engineering
---

# Deep foundation types and use of shallow foundations

Building Technology · Chapter 2: Foundations

- Asked in: 2079 Asoj, 6 marks
- Video: [Types of Foundation | Types of Footing | Types of Foundation in civil Engineering](https://www.youtube.com/watch?v=dO2lWAT-ltk) — Visual Civil
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/deep-shallow-types-079a
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-2

## Question

List types of deep foundation and critically illustrate on the use of various shallow foundations with sketches.

## Short answer

Deep foundations include pile, pier, well or caisson, drilled shafts, and under-reamed piles. Shallow foundations are used as follows: strip under walls, isolated under single columns, combined for close columns, strap for edge columns, raft for weak soil and heavy loads, grillage for very heavy loads, and stepped footing on slopes.

## Answer

#### Types of deep foundation
1. **Pile foundation**: Slender columns driven or bored into the ground; end-bearing, friction, or both; materials: timber, concrete (precast, cast-in-situ), steel.
2. **Pier foundation**: A large-diameter shaft of masonry or concrete carrying heavy loads to firm strata.
3. **Well (caisson) foundation**: A hollow cylinder or box sunk to the required depth, used for bridges.
4. **Drilled shafts** and **under-reamed piles**.

#### Use of various shallow foundations
| Type | Where it is used |
|---|---|
| Strip / wall footing | Under load-bearing walls on firm soil |
| Isolated spread footing | Under single columns of RCC frames where soil is good |
| Combined footing | Columns close together or near the property line |
| Strap footing | An edge column near the boundary, where an isolated footing would be eccentric |
| Raft (mat) | Weak soil, heavy loads, basements; when footings would cover over half the area |
| Grillage | Very heavy loads on soil of low bearing capacity, with less depth |
| Stepped footing | Sloping ground |

```text
 Combined:  [col1]  [col2]       Raft: |c|c|c|
            [___________]              ____________
 Strap:  [F1]=====strap=====[F2]
```
Shallow foundations are cheap and quick; when the soil near the surface is weak, or when depth is needed against scour or uplift, deep foundations are chosen.

## Check yourself

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

1. Which is a deep foundation type?
   A. Strip footing
   B. Well (caisson) foundation
   C. Strap footing
   D. Isolated footing
   Answer: B. Piles, piers, wells/caissons and drilled shafts are deep foundations. (Key point: Deep foundation types)

2. Where is a strap footing used?
   A. On sloping ground
   B. For very heavy loads on rock
   C. Edge column near the boundary where an isolated footing would be eccentric
   D. Under walls on firm soil
   Answer: C. The strap beam balances eccentricity of the edge column. (Key point: Strap footing use)

3. Stepped footing is used on:
   A. Rock only
   B. Under water
   C. Sloping ground
   D. Flat clay
   Answer: C. Stepped foundations suit sloping ground for walls. (Key point: Stepped footing)

4. When are deep foundations chosen over shallow ones?
   A. When surface soil is weak or depth is needed for scour or uplift
   B. When the soil near the surface is strong
   C. When the building is a single storey
   D. To reduce cost always
   Answer: A. Shallow foundations are cheap, but deep ones are used when near-surface soil is weak or depth is needed. (Key point: Deep vs shallow)

## Related in Building Technology

- [Types of shallow foundation](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Ashallow-foundation-types) — Building Technology, chapter 2
- [Foundation requirements and shallow foundation types](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Afoundation-define-requirements-shallow) — Building Technology, chapter 2
- [Functions of foundation, deep foundation types](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Afoundation-functions-deep) — Building Technology, chapter 2
- [Foundations on black cotton soil](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Ablack-cotton-foundation) — Building Technology, chapter 2
- [Excavating foundation trenches in water-logged ground](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aexcavation-wet-methods) — Building Technology, chapter 2, 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×

## Related in other subjects

- [Classify shallow and deep foundations](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Aclassify-foundations-soil) — Foundation Engineering, chapter 1, asked 4×
- [Shallow versus deep foundation](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Ashallow-vs-deep-foundation) — Foundation Engineering, chapter 1
- [Shallow and deep wells](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Ashallow-deep-wells) — Water Supply Engineering, chapter 2, asked 4×
- [When piles are preferred to shallow foundations](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Apile-vs-shallow-conditions) — Foundation Engineering, chapter 8, asked 3×