---
title: "Mortar and estimation of mortar requirement"
subject: "Building Technology"
chapter: 3
key: "semester_6/building_technology:what-is-mortar-estimation"
source: https://www.bctengineer.com/q/semester_6/building_technology/what-is-mortar-estimation
site: BCT Engineering
---

# Mortar and estimation of mortar requirement

Building Technology · Chapter 3: Mortars & Masonry works

- Asked in: 2071 Bhadra, 8 marks
- Video: [MORTAR Estimation for Brickwork| Sand and Cement Calculation required for Brickwork](https://www.youtube.com/watch?v=jXZTAUyXPl8) — Ian Construction
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/what-is-mortar-estimation
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-3

## Question

What is mortar? Describe the estimation of mortar requirement.

## Short answer

Mortar is a workable paste of binder, sand and water for bonding masonry. Estimation: subtract solid brick volume from masonry volume to get wet mortar; dry volume = wet × 1.27. For 1:n mix, cement = dry volume/(1+n) and sand = n × dry volume/(1+n).

## Answer

#### Mortar
Mortar is a paste of binding material (cement or lime), fine aggregate (sand) and water; it is used to join bricks or stones, fill joints and plaster surfaces. Common types are cement mortar (1:3 to 1:6), lime mortar, cement-lime (gauged) mortar and mud mortar.

#### Estimation of mortar requirement
The mortar needed depends on the volume of masonry and the volume of units in it.

1. Find the volume of brickwork $V$ (m³).
2. Find the size of a brick with mortar, e.g. $(240+10)\times(115+10)\times(57+10)$ mm, and the number of bricks $N = V/\text{volume of one brick with mortar}$.
3. Volume of bricks without mortar $= N \times 0.24 \times 0.115 \times 0.057$.
4. **Wet volume of mortar** $= V - $ volume of bricks.
5. **Dry volume** $=$ wet volume $\times$ 1.27 (to account for voids in sand, shrinkage and wastage).
6. Divide by the mix ratio $1:n$: cement $= \dfrac{\text{dry volume}}{1+n}$, sand $= \dfrac{n}{1+n}\times\text{dry volume}$.
7. Convert cement to bags: 1 bag (50 kg) $= 0.0347$ m³.

#### Worked example (10 m³ brickwork, 1:6)
- Bricks $= 10/(0.25\times0.125\times0.067) \approx 4777$.
- Brick volume $= 4777 \times 0.0015732 = 7.515$ m³.
- Wet mortar $= 10 - 7.515 = 2.485$ m³; dry $= 2.485 \times 1.27 = 3.156$ m³.
- Cement $= 3.156/7 = 0.451$ m³ ($\approx$ 13 bags); sand $= 3.156 \times 6/7 = 2.705$ m³.

For plaster: mortar volume $=$ area $\times$ thickness $\times$ 1.27 (dry).

## Check yourself

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

1. What is mortar?
   A. A mixture of cement, sand and coarse aggregate
   B. A paste of binder, fine aggregate and water used to join units and plaster
   C. A fired clay unit
   D. Cement and water only
   Answer: B. Mortar has binder (cement or lime), sand and water; no coarse aggregate. (Key point: Definition of mortar)

2. In estimating mortar, how is wet volume found?
   A. Number of bricks times brick volume with mortar
   B. Volume of masonry times mix ratio
   C. Dry volume divided by 1.27 minus bricks
   D. Volume of masonry minus volume of the units without mortar
   Answer: D. Wet mortar = V - N x (volume of one brick without mortar). (Key point: Wet volume)

3. Why is the dry volume taken as 1.27 times the wet volume?
   A. Cement bags are 1.27 times bigger
   B. To account for voids in sand, shrinkage and wastage
   C. Because bricks absorb 27% of mortar
   D. To convert m^3 to kg
   Answer: B. Dry materials bulk more than the finished mortar, and some is wasted. (Key point: Dry volume factor)

4. For mix 1:n and dry volume Vd, which is correct?
   A. Cement = Vd/n, sand = Vd
   B. Cement = Vd/(1+n), sand = n Vd/(1+n)
   C. Cement = n Vd, sand = Vd/n
   D. Cement = Vd/(1+n), sand = Vd/(1+n)
   Answer: B. Parts are 1 and n out of total 1+n. (Key point: Cement and sand formula)

## Related in other subjects

- [Double room: excavation, CRS, brick, plaster](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Adouble-room-d) — Estimating and Costing, chapter 6