---
title: "Underground RCC tank: brick, PCC, steel (1% steel)"
subject: "Estimating and Costing"
chapter: 6
key: "semester_7/estimating_and_costing:ug-tank-b-fig1"
source: https://www.bctengineer.com/q/semester_7/estimating_and_costing/ug-tank-b-fig1
site: BCT Engineering
---

# Underground RCC tank: brick, PCC, steel (1% steel)

Estimating and Costing · Chapter 6: Detailed Estimate

- Asked in: 2082 Baisakh, 3×3 marks
- Video: [Quantity Survey: Underground water tank.](https://www.youtube.com/watch?v=fCuGzkwlqTE) — Engr Suliman Khan
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/estimating_and_costing/ug-tank-b-fig1
- 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 an underground RCC water tank given in Figure 1.
i) Brickwork
ii) PCC for RCC works
iii) Steel reinforcement in RCC works (assume 1% steel)
[Figure 1 not included in the scanned paper]

## Short answer

On assumed dimensions, brickwork by centre-line method: 3.767 m³. PCC for floor and top slab (deducting manhole) is 2.255 m³. Steel at 1% of RCC volume weighs177.0 kg.

## Answer

Figure 1 is not available, so the working is shown on assumed dimensions; the method is the same for any drawing.

#### Assumed dimensions

- Clear internal size $3.00 \times 2.00$ m, clear depth $1.50$ m.
- Brick walls $0.23$ m thick in 1:4 mortar, $1.50$ m high, resting on a $0.15$ m RCC floor.
- RCC floor $0.15$ m thick and top cover slab $0.12$ m thick, both of outer size $(3.00 + 0.46) \times (2.00 + 0.46) = 3.46 \times 2.46$ m; a $0.60 \times 0.60$ m manhole opening in the cover.
- Steel $1\%$ of the volume of RCC; density $7850$ kg/m³.

#### i) Brickwork (centre-line method)

Centre-line length $= 2\,[(3.00 + 0.23) + (2.00 + 0.23)] = 10.92$ m

$V = 10.92 \times 0.23 \times 1.50 = 3.767$ m³

#### ii) PCC (concrete) for the RCC works

| Member | Working | Volume (m³) |
|---|---|---:|
| Floor slab | $3.46 \times 2.46 \times 0.15$ | 1.277 |
| Top slab | $3.46 \times 2.46 \times 0.12$ | 1.021 |
| Deduct manhole | $0.60 \times 0.60 \times 0.12$ | −0.043 |
| **Total** | | **2.255** |

#### iii) Steel reinforcement

$W = 1\% \times 2.255 \times 7850 = 177.0$ kg

**Answer (for the assumed figure): brickwork = 3.767 m³; concrete in RCC = 2.255 m³; steel = 177.0 kg.**

## Check yourself

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

1. How is the brickwork wall length obtained?
   A. Centre-line: 2[(3.00+0.23)+(2.00+0.23)] = 10.92 m
   B. 2(3.00 + 2.00) = 10.00 m
   C. 2[(3.00+0.46)+(2.00+0.46)] = 11.84 m
   D. 3.00 x 2.00 = 6 m
   Answer: A. The centre line of the wall is clear size plus one wall thickness each way. (Key point: Brickwork length)

2. How is steel weight found when 1% steel is assumed?
   A. 1% of the brickwork volume x 7850
   B. 1% of the RCC volume x 7850 kg/m3
   C. 1% of the RCC area x 7850
   D. 0.01 x RCC volume in kg
   Answer: B. Steel volume = 1% of concrete volume, converted to weight by density 7850 kg/m3. (Key point: Steel from percentage)

3. What is done with the 0.60 x 0.60 manhole in the cover slab?
   A. It is added to the slab
   B. It is ignored
   C. Its volume is deducted from the slab concrete
   D. It is deducted from the floor slab
   Answer: C. The opening has no concrete, so 0.6 x 0.6 x 0.12 is deducted. (Key point: Manhole opening)

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