---
title: "Double room: excavation, CRS, brick, plaster"
subject: "Estimating and Costing"
chapter: 6
key: "semester_7/estimating_and_costing:double-room-d"
source: https://www.bctengineer.com/q/semester_7/estimating_and_costing/double-room-d
site: BCT Engineering
---

# Double room: excavation, CRS, brick, plaster

Estimating and Costing · Chapter 6: Detailed Estimate

- Asked in: 2081 Baisakh, 4×4 marks
- Video: [(Part I: Earthwork) Estimation of two roomed building (long wall short wall method)](https://www.youtube.com/watch?v=4x4oRRwJb3s) — CIVIL ENGINEERING By Karthivelu S
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/estimating_and_costing/double-room-d
- Whole chapter: https://www.bctengineer.com/md/semester_7/estimating_and_costing/chapter-6

## Question

Calculate the quantities from the given building drawings: Fig. 1(a, b)
a) Earthwork in excavation
b) Crushed rubble stone masonry
c) 1st class brick work in super structure
d) 12 mm plastering work 1:4 for inner wall
Following are the double room building estimation specifications:
- In foundation cement concrete M25 is used.
- CRS wall is used in the foundation for the base of the brick wall.
- Plinth beam size is 400 mm × 600 mm in cement concrete M25.
- Damp-proof course 25 mm thick is applied.
- In superstructure 1st class brickwork is in 1:4 cement mortar and thickness 300 mm.
- Doors D, size 1.2 m × 2.1 m
- Windows W, size 1 m × 1.5 m
- Shelves S-1 m × 1.5 m
[Fig. 1(a, b) not included in the scanned paper]

## Short answer

Using an assumed double-room layout, centre-line method gives excavation 36.30 m³, crushed rubble stone masonry 10.54 m³, first-class brickwork 21.70 m³, and 12 mm inner plaster 80.46 m².

## Answer

Fig. 1 is not available, so an assumed **double-room building** is used with the given specifications.

#### Assumed data
- Two rooms side by side, each 4.0 m × 3.5 m clear; all walls 300 mm (as stated). Outside size = (2 × 4.0 + 3 × 0.3) × (3.5 + 2 × 0.3) = 8.90 × 4.10 m.
- Centre-line length of outer walls = 2[(8.90 − 0.3) + (4.10 − 0.3)] = 24.80 m. The partition is 3.5 + 0.3 = 3.80 m between the centre lines of the outer walls; at each of its two T-junctions it is shortened by half the width of the outer-wall item, so its length is 3.80 − 1.10 = 2.70 m for the trench, 3.80 − 0.50 = 3.30 m for the CRS and 3.80 − 0.30 = 3.50 m for the brickwork.
- Foundation: trench 1.10 m wide, 1.20 m deep; CC M25 bed 0.30 m; CRS wall 0.50 m wide, 0.75 m high from top of bed to bottom of plinth beam (0.15 m below GL); plinth beam 400 × 600 mm (not asked).
- Superstructure 3.0 m high above plinth beam; D 1.2 × 2.1 (2 nos.), W 1.0 × 1.5 (3 nos.), shelf recess S 1.0 × 1.5 × 0.15 m deep (2 nos.). Plaster 12 mm 1:4.

#### a) Earthwork in excavation
| Item | No. | L (m) | B (m) | H/D (m) | Qty (m³) |
|---|---|---|---|---|---|
| Trench, outer walls | 1 | 24.800 | 1.100 | 1.200 | 32.736 |
| Trench, partition (3.80 − 1.10) | 1 | 2.700 | 1.100 | 1.200 | 3.564 |
| **Total** | | | | | **36.300** |

#### b) Crushed rubble stone masonry
| Item | No. | L (m) | B (m) | H/D (m) | Qty (m³) |
|---|---|---|---|---|---|
| CRS masonry, outer walls, 0.50 wide × 0.75 high | 1 | 24.800 | 0.500 | 0.750 | 9.300 |
| CRS masonry, partition (3.80 − 0.50) | 1 | 3.300 | 0.500 | 0.750 | 1.238 |
| **Total** | | | | | **10.538** |

(For reference, M25 concrete bed = (24.80 + 2.70) × 1.10 × 0.30 = 9.08 m³.)

#### c) 1st class brick work in superstructure (1:4)
| Item | No. | L (m) | B (m) | H/D (m) | Qty (m³) |
|---|---|---|---|---|---|
| Wall 0.30 × 3.0 above plinth beam (24.80 + 3.50) | 1 | 28.300 | 0.300 | 3.000 | 25.470 |
| Deduct doors D 1.2 × 2.1 (2 nos.) | -2 | 1.200 | 0.300 | 2.100 | -1.512 |
| Deduct windows W 1.0 × 1.5 (3 nos.) | -3 | 1.000 | 0.300 | 1.500 | -1.350 |
| Deduct shelves S 1.0 × 1.5 × 0.15 recess (2 nos.) | -2 | 1.000 | 0.150 | 1.500 | -0.450 |
| Deduct lintels over doors | -2 | 1.600 | 0.300 | 0.150 | -0.144 |
| Deduct lintels over windows and shelves | -5 | 1.400 | 0.300 | 0.150 | -0.315 |
| **Total** | | | | | **21.699** |

#### d) 12 mm plastering, 1:4, inner wall
| Item | No. | L (m) | B (m) | H/D (m) | Qty (m²) |
|---|---|---|---|---|---|
| Inside walls, both rooms 2 × 2(4.0+3.5) × 3.0 | 1 | 30.000 | 3.000 | – | 90.000 |
| Deduct doors (one inside face each) | -2 | 1.200 | 2.100 | – | -5.040 |
| Deduct windows | -3 | 1.000 | 1.500 | – | -4.500 |
| **Total** | | | | | **80.460** |

**Answer:** Excavation 36.30 m³; CRS 10.54 m³; brickwork 21.70 m³; plaster 80.46 m² (assumed layout).

## Check yourself

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

1. What length is used for trench of double room building?
   A. Outer centre-line 24.80 + partition 3.5 = 28.30 m
   B. 24.80 m only
   C. 3.5 m
   D. 8.9 + 4.1
   Answer: A. The trench runs under outer walls and partition. (Key point: Total wall length)

2. How is crushed rubble stone masonry computed?
   A. 28.30 x 0.50 x 0.75
   B. 28.30 x 1.10 x 1.20
   C. 28.30 x 0.30 x 3.0
   D. 28.30 x 1.10 x 0.30
   Answer: A. CRS wall is 0.50 m wide and 0.75 m high along total wall length. (Key point: CRS masonry)

3. How is shelf S deducted from brickwork?
   A. As recess 1.0 x 0.15 depth x 1.5
   B. Full 0.30 thickness
   C. Ignored
   D. Window size
   Answer: A. A shelf is a recess, so only the 0.15 m depth removed. (Key point: Shelf recess deduction)

4. In inside plaster, how many doors are deducted?
   A. One per room, 2 doors in total
   B. One
   C. Four
   D. None
   Answer: A. Each door is seen once inside each room. (Key point: Inside plaster deductions)

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