---
title: "RCC frame building: excavation, brick, plaster"
subject: "Estimating and Costing"
chapter: 6
key: "semester_7/estimating_and_costing:rcc-frame-two-room-e"
source: https://www.bctengineer.com/q/semester_7/estimating_and_costing/rcc-frame-two-room-e
site: BCT Engineering
---

# RCC frame building: excavation, brick, plaster

Estimating and Costing · Chapter 6: Detailed Estimate

- Asked in: 2080 Bhadra, 3+4+3 marks
- Video: [Estimate & Costing of Building Structure | Part-3](https://www.youtube.com/watch?v=2s52VrqpUfU) — Tutorials Tips
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/estimating_and_costing/rcc-frame-two-room-e
- Whole chapter: https://www.bctengineer.com/md/semester_7/estimating_and_costing/chapter-6

## Question

Prepare detailed estimate for the following items of works for RCC frame structured building (Fig. 2.)
i) Earthwork in excavation in foundation
ii) Brickwork in 1:4 c/s mortar up to plinth level
iii) 1:4 (c/s) mortar inside the room
[Figure 2: two-room building. Overall 7000 mm × 4700 mm outer; Room 1 3180 × 3040 mm, Room 2 3130 × 3040 mm, verandah 7000 × 1200 mm. Openings: D1 1000 × 2100 mm, W1 1500 × 1350 mm, W2 1000 × 1350 mm. Plinth tie-beam 300 × 300 mm; superstructure wall thickness 230 mm (same section for exterior and partition walls). Section A-A: height 2850 mm, M20 RCC slab 125 mm with 600 mm projection, brickwork 1:6 in superstructure, 1:4 brickwork in plinth (450 mm), foundation with 75 mm PCC, brick soling, compacted earth, PCC (1:2:4); footing widths 600/400/300 mm; heights 300/150/350/150 mm. All dimensions in mm, not to scale.]

## Short answer

Centre-line method from the figure gives foundation excavation 10.92 m³, brickwork in 1:4 up to plinth 4.04 m³, and 12 mm inside plaster 63.05 m² (mortar volume 0.757 m³).

## Answer

#### Reading of the figure
The outer building is 7000 × 4700 mm including the 1200 mm verandah, so the rooms (and walls) occupy 7000 × 3500 mm (3040 + 2 × 230 = 3500; 3180 + 3130 + 3 × 230 = 7000). Walls are 230 mm. The verandah is open and not walled. Assumptions: one door D1 in each room, W1 in Room 1, W2 in Room 2.

Foundation: concrete 0.60 m wide × 0.30 m thick, brick step 0.40 m × 0.15 m, 230 mm wall; trench depth taken as 0.30 + 0.15 + 0.35 = 0.80 m; plinth 0.45 m above GL; 300 × 300 RCC tie beam at the top of the plinth.

Centre-line length of outer walls = 2[(7.0 − 0.23) + (3.5 − 0.23)] = 20.08 m. The partition is 3.04 + 0.23 = 3.27 m between the outer-wall centre lines; at its two T-junctions it is shortened by half the width of the outer-wall item at each end: trench 3.27 − 0.60 = 2.67 m, brick step 3.27 − 0.40 = 2.87 m, wall 3.27 − 0.23 = 3.04 m.

#### i) Earthwork in excavation in foundation
| Item | No. | L (m) | B (m) | H/D (m) | Qty (m³) |
|---|---|---|---|---|---|
| Trench, outer walls | 1 | 20.080 | 0.600 | 0.800 | 9.638 |
| Trench, partition (3.27 − 0.60) | 1 | 2.670 | 0.600 | 0.800 | 1.282 |
| **Total** | | | | | **10.920** |

#### ii) Brickwork in 1:4 c/s mortar up to plinth level
Wall height = 0.35 (below GL) + 0.45 (plinth) − 0.30 (tie beam) = 0.50 m. Brickwork below plinth level runs continuously under the doors, so no deduction is made for door openings.

| Item | No. | L (m) | B (m) | H/D (m) | Qty (m³) |
|---|---|---|---|---|---|
| Brick step 0.40 × 0.15 (20.08 + 2.87) | 1 | 22.950 | 0.400 | 0.150 | 1.377 |
| Wall 0.23 up to plinth tie beam (20.08 + 3.04) | 1 | 23.120 | 0.230 | 0.500 | 2.659 |
| **Total** | | | | | **4.036** |

#### iii) 1:4 cement-sand plaster inside the rooms (12 mm assumed)
Clear height 2.85 m.

| Item | No. | L (m) | B (m) | H/D (m) | Qty (m²) |
|---|---|---|---|---|---|
| Room 1 walls | 1 | 12.440 | 2.850 | – | 35.454 |
| Room 2 walls | 1 | 12.340 | 2.850 | – | 35.169 |
| Deduct D1 1.0 × 2.1 (2 nos.) | -2 | 1.000 | 2.100 | – | -4.200 |
| Deduct W1 1.5 × 1.35 | -1 | 1.500 | 1.350 | – | -2.025 |
| Deduct W2 1.0 × 1.35 | -1 | 1.000 | 1.350 | – | -1.350 |
| **Total** | | | | | **63.048** |

Mortar volume at 12 mm = 63.05 × 0.012 = 0.757 m³.

**Answer:** Excavation 10.92 m³; brickwork to plinth 4.04 m³; inside plaster 63.05 m².

## Check yourself

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

1. Why are rooms taken as 7000 x 3500 mm?
   A. Verandah 1200 mm is open and not walled
   B. Verandah is plastered
   C. Rooms are 4700 mm
   D. It is a guess
   Answer: A. Only 7000 x 3500 is enclosed by walls. (Key point: Verandah)

2. How is wall height 0.50 m up to the tie beam found?
   A. 0.35 + 0.45 - 0.30
   B. 0.35 + 0.45 + 0.30
   C. 0.45
   D. 0.80
   Answer: A. Below GL part plus plinth less beam depth. (Key point: Plinth wall height)

3. What trench width and depth are used?
   A. 0.60 m and 0.80 m
   B. 0.23 and 0.45
   C. 0.40 and 0.15
   D. 1.0 and 1.0
   Answer: A. Concrete 0.60 m wide, depth 0.30 + 0.15 + 0.35 = 0.80 m. (Key point: Trench excavation)

4. Room 1 is 3.18 x 3.04 clear. Its plaster perimeter?
   A. 2(3.18 + 3.04) = 12.44 m
   B. 3.18 + 3.04
   C. 2(3.18+3.04+0.46)
   D. 4 x 3.04
   Answer: A. Inside perimeter uses clear dimensions. (Key point: Room perimeter)

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