---
title: "Detailed specification of cement sand mortar 1:4"
subject: "Construction Management"
chapter: 12
key: "semester_8/construction_management:detailed-spec-cs-mortar-1-4"
source: https://www.bctengineer.com/q/semester_8/construction_management/detailed-spec-cs-mortar-1-4
site: BCT Engineering
---

# Detailed specification of cement sand mortar 1:4

Construction Management · Chapter 12: Specification

- Asked in: 2068 Bhadra (old course)
- Video: [Cement & Sand Calculation for Brickwork | Mortar Calculation in CFT | Easy Method with example](https://www.youtube.com/watch?v=-hwnGLf9aws) — Zain Ul Abedin 
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_8/construction_management/detailed-spec-cs-mortar-1-4
- Whole chapter: https://www.bctengineer.com/md/semester_8/construction_management/chapter-12

## Question

Write down the detailed specification for cement sand mortar (1:4).

## Short answer

Cement sand mortar 1:4 by volume, mixed uniformly with minimum water, used within 30 minutes without re-tempering. 28-day cube strength approximately 7–10 N/mm². Measured by volume (m³).

## Answer

#### Detailed specification: cement sand mortar 1:4

**Scope:** Preparation of cement sand mortar in the proportion of 1 part cement to 4 parts sand by volume, for use in brickwork, plastering and other work.

**Materials**
- **Cement:** OPC 43 grade/PPC conforming to the relevant Nepal Standard/IS; fresh, free from lumps, stored in a dry shed on a raised platform and used in order of delivery.
- **Sand:** clean, hard, well-graded river or pit sand, free from clay, silt (< 4%), mica, salts and organic matter; fineness modulus 1.5–2.5 (for plastering, finer sand of FM about 1.0–1.5, passing a 2.36 mm sieve).
- **Water:** clean, potable, free from oil, acid, alkali and organic matter.

**Proportion:** 1 : 4 by volume. One 50 kg bag of cement is taken as 0.035 m³, and sand is measured in a gauge box. For about 1 m³ of mortar, around 8–9 bags of cement and 1.15–1.2 m³ of sand are required (indicative).

**Mixing**
- By mixer: dry mix until uniform, then add water for the required consistency, and mix for at least 2 minutes.
- By hand: on a clean watertight platform; mix the dry sand and cement until the colour is uniform, then add water gradually and turn the mix over at least three times.
- Use only the minimum water necessary for a workable mix.

**Use:** Mortar must be used within **30 minutes** of adding water; if it starts setting it must be discarded; no re-tempering.

**Testing:** The 28-day compressive strength of 70.6 mm cubes (about 7–10 N/mm²) may be checked as the engineer instructs.

**Measurement and payment:** Measured by volume (m³) when paid separately; otherwise included in the rate of the item in which it is used.

## Check yourself

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

1. What happens to mortar that has begun to set?
   A. It is retempered with water
   B. It is used for plaster
   C. It is discarded; use within 30 minutes of adding water, no re-tempering
   D. It is mixed with fresh cement
   Answer: C. Mortar must be used within 30 minutes; setting mortar is rejected. (Key point: Use time)

2. What is the correct mixing sequence?
   A. Dry mix cement and sand till uniform colour, then add minimum water gradually
   B. Add water first, then sand
   C. Mix cement and water only
   D. Mix sand with excess water
   Answer: A. Dry mixing ensures uniformity; water is the minimum needed for workability. (Key point: Mixing)

3. Which sand requirement is correct?
   A. Silt more than 10%
   B. Sea sand with salts
   C. Clean, hard sand with silt below 4% and fineness modulus 1.5-2.5
   D. Fine clayey sand
   Answer: C. Sand must be clean and hard, silt under 4%, FM about 1.5-2.5. (Key point: Sand quality)

## Close variants set in other exams

- [Detailed specification of cement sand mortar 1:6](https://www.bctengineer.com/question.md?key=semester_8%2Fconstruction_management%3Adetailed-spec-cs-mortar-1-6) — Construction Management, chapter 12, asked 2×

## Related in Construction Management

- [Detailed specification of brick work in 1:4 mortar](https://www.bctengineer.com/question.md?key=semester_8%2Fconstruction_management%3Adetailed-spec-brick-1-4) — Construction Management, chapter 12, asked 5×
- [Detailed specification of brick work in 1:6 mortar](https://www.bctengineer.com/question.md?key=semester_8%2Fconstruction_management%3Adetailed-spec-brick-1-6) — Construction Management, chapter 12, asked 5×
- [Detailed specification of cement plaster 1:4](https://www.bctengineer.com/question.md?key=semester_8%2Fconstruction_management%3Adetailed-spec-plaster-1-4) — Construction Management, chapter 12
- [Detailed specification of stone masonry in 1:6 mortar](https://www.bctengineer.com/question.md?key=semester_8%2Fconstruction_management%3Adetailed-spec-stone-masonry-1-6) — Construction Management, chapter 12
- [Types of specification: general and detailed](https://www.bctengineer.com/question.md?key=semester_8%2Fconstruction_management%3Aspec-types-general-detailed) — Construction Management, chapter 12, asked 7×
- [Detailed specification of RCC M20 column](https://www.bctengineer.com/question.md?key=semester_8%2Fconstruction_management%3Adetailed-spec-rcc-m20-column) — Construction Management, chapter 12

## Related in other subjects

- [Mortar properties; cement and sand for 10 cum](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Amortar-quantity-10cum) — Building Technology, chapter 3
- [Preparing cement mortar by manual process](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Amortar-prep-manual) — Building Technology, chapter 3, asked 2×