---
title: "Short note: Mortars used in plastering"
subject: "Building Technology"
chapter: 3
key: "semester_6/building_technology:mortars-plastering-short"
source: https://www.bctengineer.com/q/semester_6/building_technology/mortars-plastering-short
site: BCT Engineering
---

# Short note: Mortars used in plastering

Building Technology · Chapter 3: Mortars & Masonry works

- Asked in: 2074 Bhadra, 4 marks
- Video: [plastering | types of mortars used in plastering | civil engineering | cement plastering](https://www.youtube.com/watch?v=jsRpZWAXE4c) — Civil Engineering CE
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/mortars-plastering-short
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-3

## Question

Write a short note on mortars used in plastering works.

## Short answer

Plastering mortars include cement mortar (1:3 to 1:6), lime mortar (1:2 to 1:3), cement-lime gauged mortar (1:1:6), mud mortar, and gypsum plaster. Thickness varies: 12 mm internal, 15-20 mm external, 6 mm ceiling. Surface preparation includes cleaning, raking joints, wetting, and curing for at least 7 days.

## Answer

**Plastering** is the covering of walls, ceilings and other rough surfaces with a layer of mortar to protect them and give a smooth, decorative finish. The mortar must be workable, adhere well and be durable.

#### Mortars used
| Mortar | Mix | Use |
|---|---|---|
| Cement mortar | 1:3 to 1:6 (cement : sand) | External plaster 1:4; internal 1:6; ceiling 1:3 |
| Lime mortar | 1:2 to 1:3 (lime : sand) | Old/heritage works, internal plaster |
| Cement-lime (gauged) mortar | 1:1:6 | Good adhesion, workable, internal and external |
| Mud mortar | Clay + straw | Rural houses of Nepal |
| Gypsum plaster | Gypsum + water | Internal smooth finish |

#### Practice
- Thickness: 12 mm for internal brick walls, 15-20 mm for external walls and 6 mm for ceilings; in two-coat work the finishing coat is about 6 mm.
- The surface is cleaned, the joints are raked to give a key, and the surface is wetted; plaster is then applied between level guides (screeds).
- Plaster is cured for at least 7 days.

Sand should be clean, well graded and free from clay and silt.

## Check yourself

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

1. Why plaster?
   A. Join bricks
   B. Reduce wall thickness
   C. Protect surfaces and give smooth finish
   D. Increase strength of bricks
   Answer: C. Plaster covers rough surfaces to protect and finish them. (Key point: Plastering purpose)

2. Which is typical for external plaster?
   A. 1:20
   B. 1:1
   C. 1:4
   D. 1:12
   Answer: C. External 1:4, internal 1:6, ceiling 1:3. (Key point: Cement mortar mixes)

3. Gauged mortar is?
   A. Gypsum and water
   B. Lime only
   C. Cement-lime-sand mix like 1:1:6
   D. Mud with straw
   Answer: C. It gives good adhesion and workability. (Key point: Gauged mortar)

4. Plaster should be cured for at least?
   A. 7 days
   B. 3 hours
   C. 60 days
   D. 1 day
   Answer: A. Curing at least 7 days. (Key point: Curing)

## Related in Building Technology

- [Pointing, plastering defects, oil paint constituents](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Apointing-plaster-defects-paint) — Building Technology, chapter 9, asked 2×
- [Pointing versus plastering](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Apointing-vs-plastering) — Building Technology, chapter 9, asked 2×

## Related in other subjects

- [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
- [Contract types in civil engineering; govt works](https://www.bctengineer.com/question.md?key=semester_8%2Fconstruction_management%3Acontract-types-government) — Construction Management, chapter 5
- [Why timber is used; seasoning method](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aseasoning-method-and-timber-use) — Civil Engineering Materials, chapter 7