---
title: "Short note: Basement and retaining wall"
subject: "Building Technology"
chapter: 3
key: "semester_6/building_technology:short-basement-retaining-wall"
source: https://www.bctengineer.com/q/semester_6/building_technology/short-basement-retaining-wall
site: BCT Engineering
---

# Short note: Basement and retaining wall

Building Technology · Chapter 3: Mortars & Masonry works

- Asked in: 2064 Jestha (old course), 4 marks
- Video: [BASEMENT RETAINING WALLS CONSTRUCTION](https://www.youtube.com/watch?v=w-0_KQTCLTU) — TATIAN SMART TECHNOLOGY CONSTRUCTION
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/short-basement-retaining-wall
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-3

## Question

Write a short note on basement and retaining wall.

## Short answer

A basement is a storey below ground level requiring RCC retaining walls (200-300 mm) with waterproofing, drainage, ventilation, and fire exits. A retaining wall holds back earth, designed against overturning, sliding, and bearing failure under active earth pressure Pa = 0.5 KaγH² acting at H/3, with weep holes for drainage.

## Answer

#### Basement
A **basement** is the storey of a building that is wholly or partly below ground level, used for parking, storage, services or shops. Its walls must resist earth pressure and ground water, so they are built as retaining walls (RCC, 200-300 mm thick) with a **waterproofing** (tanking) layer. Requirements: damp-proof floor and walls, drainage around the walls, adequate ventilation, lighting and fire exits, and a proper ramp or stair.

Waterproofing methods: integral waterproofing compound, bituminous membrane, cement plaster with a waterproofer, and drainage (French drain, sump pump).

#### Retaining wall
A **retaining wall** holds back earth where the ground level changes suddenly. Its types are gravity, cantilever, counterfort and buttress walls. It must be designed against overturning, sliding and bearing failure under the active earth pressure $P_a = \tfrac12 K_a\gamma H^2$, acting at $H/3$ from the base. Weep holes and filters behind the wall prevent the build-up of water pressure.

```text
  ground level
 ------------+    +
   backfill  |    |
   (soil)    |wall|    basement
    P_a ---> |    |    (inside)
             |    |
 ____________|    |_____________
          ===========  footing
```

## Check yourself

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

1. What is a basement?
   A. Roof space
   B. Top floor
   C. Plinth only
   D. Storey wholly or partly below ground level
   Answer: D. It is used for parking, storage or services. (Key point: Basement)

2. Why do basement walls need tanking?
   A. To resist ground water and earth pressure
   B. To increase height
   C. For appearance
   D. To hold roof
   Answer: A. They are retaining walls exposed to water. (Key point: Waterproofing)

3. A retaining wall must be checked against?
   A. Overturning, sliding and bearing failure
   B. Fire
   C. Wind uplift
   D. Only sliding
   Answer: A. These are the standard stability checks. (Key point: Retaining wall stability)

4. Active earth pressure is Pa = 0.5 Ka gamma H^2 acting at?
   A. H/3 from base
   B. H from base
   C. H/2 from base
   D. 2H/3 from base
   Answer: A. Triangular pressure acts at one third height. (Key point: Earth pressure)

## Related in Building Technology

- [Short note: Retaining wall](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Ashort-retaining-wall) — Building Technology, chapter 3, asked 2×
- [Parapet wall, gravity and counterfort retaining walls](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aparapet-retaining-counterfort) — Building Technology, chapter 3
- [Basement floor and its waterproofing](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Abasement-waterproofing) — Building Technology, chapter 1, asked 2×

## Related in other subjects

- [Braced cut design versus retaining wall](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Abracing-vs-retaining-wall) — Foundation Engineering, chapter 4, asked 2×
- [Passive thrust on retaining wall back](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Awall-passive-thrust-two-layer) — Foundation Engineering, chapter 3
- [Stability checks of retaining walls](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Astability-checks-retaining-wall) — Foundation Engineering, chapter 3, asked 2×
- [Active thrust, 6 m wall, sand over clay](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Atwo-layer-wall-6m-sand-clay) — Foundation Engineering, chapter 3, asked 4×