---
title: "Methods of damp proofing"
subject: "Building Technology"
chapter: 1
key: "semester_6/building_technology:damp-proofing-methods"
source: https://www.bctengineer.com/q/semester_6/building_technology/damp-proofing-methods
site: BCT Engineering
---

# Methods of damp proofing

Building Technology · Chapter 1: Functional Requirements of Buildings

- Asked in: 2081 Chaitra, 4 marks; 2075 Baisakh, 2+6 marks (asked 2 times)
- Video: [Methods of Damp Proofing - Damp Proofing - Building Materials and Construction Technology](https://www.youtube.com/watch?v=Ho9a3uXgzDY) — Ekeeda
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/damp-proofing-methods
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-1

## Question

What is damp proofing? Describe the general methods of damp proofing.

## Short answer

Damp proofing is a barrier or treatment that stops moisture entering a building; the barrier is a DPC. Methods are membrane DPC, integral waterproofing, surface treatment, cavity walls, drainage, pressure grouting, electro-osmosis, and tanking for basements.

## Answer

**Damp proofing** is the provision of a barrier or treatment that stops or reduces the entry of moisture from the ground, or from other sources, into a building. The impervious layer used is called a damp proof course (DPC).

#### General methods
1. **Membrane damp proofing (DPC)**: A continuous impervious layer is put at plinth level (and at other levels) across the full width of the wall. Materials: flexible (bitumen felt, polythene sheet, lead, copper), semi-rigid (mastic asphalt), rigid (cement concrete 1:2:4 40 mm thick, dense bricks, stone slab).
2. **Integral damp proofing**: Waterproofing compounds (pore fillers such as chalk or talc, or water repellents such as soap, alum, and Pudlo) are mixed into concrete or mortar to make it impervious.
3. **Surface treatment**: Waterproof plaster, or repellent coatings (silicones, bituminous paint, cement paint), on the wall surface; pointing of joints.
4. **Cavity wall construction**: An air gap in the wall cuts the path for moisture.
5. **Guard (surface) drains and sub-soil drainage**: Lower the water table and drain surface water away from walls; an apron round the plinth.
6. **Pressure grouting / chemical injection**: Cement grout or chemicals injected into the wall to form a barrier in existing buildings.
7. **Electro-osmosis**: Used for old buildings.
8. **Tanking** for basements: continuous waterproof membrane on floor and walls.

```text
  Wall
  ======== DPC at 150 mm above ground
  Plinth
  ~~~~~~~~ ground level
```

## Check yourself

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

1. A DPC is
   A. A plaster for fire
   B. A paint for colour
   C. A drain pipe
   D. An impervious layer that stops moisture entering the wall
   Answer: D. The impervious layer used in damp proofing is the DPC. (Key point: DPC)

2. Which is a rigid DPC material?
   A. Cement concrete 1:2:4, 40 mm thick
   B. Bitumen felt
   C. Polythene sheet
   D. Mastic asphalt
   Answer: A. Rigid: cement concrete, dense brick, stone slab; felt and polythene are flexible; mastic asphalt is semi-rigid. (Key point: Rigid DPC)

3. Integral damp proofing means
   A. Painting the wall
   B. Injecting grout into old walls
   C. Mixing waterproofing compounds into concrete or mortar
   D. Making an air gap
   Answer: C. Compounds such as Pudlo make concrete or mortar impervious. (Key point: Integral waterproofing)

4. Which method is for existing buildings?
   A. Integral waterproofing
   B. Pressure grouting or chemical injection
   C. Cavity wall
   D. Mixing alum in new mortar
   Answer: B. Grout or chemicals injected into the wall form a barrier in an existing building. (Key point: Existing buildings)

## Related in Building Technology

- [Damp proofing and defects due to moisture](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Adamp-proofing-defects) — Building Technology, chapter 1
- [Damp-proofing versus water-proofing](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Adamp-vs-waterproofing) — Building Technology, chapter 1