---
title: "Pointing, plastering defects, oil paint constituents"
subject: "Building Technology"
chapter: 9
key: "semester_6/building_technology:pointing-plaster-defects-paint"
source: https://www.bctengineer.com/q/semester_6/building_technology/pointing-plaster-defects-paint
site: BCT Engineering
---

# Pointing, plastering defects, oil paint constituents

Building Technology · Chapter 9: Finishing works

- Asked in: 2079 Jestha, 2+2+3 marks; 2078 Poush, 2+2+3 marks (asked 2 times)
- Video: [PLASTERING & POINTING | Basic Civil Engineering | By Nadish Pandey](https://www.youtube.com/watch?v=7zIgfxwxCyw) — Zero Association
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/pointing-plaster-defects-paint
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-9

## Question

Why is pointing necessary? What are the defects in plastering works? Explain various constituents of oil paint.

## Short answer

Pointing is needed to protect mortar joints from weather, prevent water ingress, and enhance appearance. Plaster defects include cracks, blistering, peeling, efflorescence, and hollowness. Oil paint constituents are base for opacity, vehicle for binding, pigment for colour, drier for curing, thinner for workability, and extender for bulk.

## Answer

#### Why pointing is necessary
- Protects the mortar joints from rain, weathering and chemical attack.
- Prevents water from seeping into the wall through the joints.
- Improves the appearance of exposed brick or stone masonry.
- Increases the life of the wall without the need for plaster.
- Cheaper than plastering.

#### Defects in plastering
- **Cracks:** caused by shrinkage, poor curing, thermal movement or a poor mortar mix.
- **Blistering:** swelling of the plaster caused by slaking of lime particles.
- **Peeling/flaking:** poor adhesion to a dirty, dry or smooth surface.
- **Efflorescence:** white salts brought to the surface by dampness.
- **Hollowness (drummy plaster):** poor bond with the background.
- **Grinning:** joint lines of the masonry show through the plaster.
- **Rust stains:** from metal or iron embedded in the wall.
- **Uneven surface**, and **popping** (small pits caused by unslaked lime particles or pebbles).

#### Constituents of oil paint
| Constituent | Function |
|---|---|
| **Base** (white lead, zinc oxide, titanium dioxide) | Gives body, opacity and covering power |
| **Vehicle** (linseed oil, poppy oil) | Carries the pigment and binds it into a film |
| **Pigment** | Gives colour |
| **Drier** (litharge, lead acetate) | Speeds up drying |
| **Thinner** (turpentine, mineral spirit) | Reduces thickness for easier application |
| **Extender/Adulterant** (barytes, chalk) | Gives bulk, reduces cost |

## Check yourself

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

1. Why is pointing necessary?
   A. It replaces foundation
   B. It protects joints from rain, prevents seepage and improves appearance of exposed masonry
   C. It insulates heat
   D. It carries wall load
   Answer: B. Pointing protects the mortar joints and the wall without full plaster. (Key point: Why pointing)

2. What causes blistering of plaster?
   A. Poor curing only
   B. Efflorescence
   C. Slaking of lime particles causing swelling
   D. Rust in wall
   Answer: C. Unslaked lime particles swell on slaking and make blisters. (Key point: Blistering)

3. What is efflorescence?
   A. Joint lines showing through plaster
   B. Hollow sound
   C. Pits from pebbles
   D. White salts coming to the surface from dampness
   Answer: D. It is white salt deposit from damp walls. (Key point: Efflorescence)

4. What is the function of the vehicle in oil paint?
   A. Carries the pigment and binds it to form a film
   B. Speeds drying
   C. Gives colour
   D. Reduces cost
   Answer: A. The vehicle (linseed oil) carries pigment and forms a hard film. (Key point: Vehicle)

## Related in Building Technology

- [Short note: Plastering and pointing](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Ashort-plastering-pointing) — Building Technology, chapter 9
- [Pointing versus plastering](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Apointing-vs-plastering) — Building Technology, chapter 9, asked 2×
- [Ingredients of an oil bound paint](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aoil-paint-ingredients) — Building Technology, chapter 9
- [Paints, oil paint ingredients, painting woodwork](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Apaints-characteristics-066bh) — Building Technology, chapter 9
- [Short note: Mortars used in plastering](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Amortars-plastering-short) — Building Technology, chapter 3
- [Paints, varnishes, painting procedures](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Apaints-varnish-064j) — Building Technology, chapter 9

## Related in other subjects

- [Paint and its constituents](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Apaint-constituents) — Engineering Chemistry, chapter 8
- [Deduction rules: brickwork, plastering, painting](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Adeduction-brick-plaster-painting) — Estimating and Costing, chapter 2
- [Functions of paint](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Afunctions-of-paint) — Civil Engineering Materials, chapter 9, asked 3×
- [Oil pressure and gas pressure HV cables](https://www.bctengineer.com/question.md?key=semester_8%2Fhigh_voltage_engineering%3Aoil-gas-pressure-cables) — High Voltage Engineering, chapter 1