---
title: "Preliminary estimate: office, 3275 m² carpet"
subject: "Estimating and Costing"
chapter: 3
key: "semester_7/estimating_and_costing:prelim-est-office-3275"
source: https://www.bctengineer.com/q/semester_7/estimating_and_costing/prelim-est-office-3275
site: BCT Engineering
---

# Preliminary estimate: office, 3275 m² carpet

Estimating and Costing · Chapter 3: Types of Estimate

- Asked in: 2082 Bhadra, 6 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/estimating_and_costing/prelim-est-office-3275
- Whole chapter: https://www.bctengineer.com/md/semester_7/estimating_and_costing/chapter-3

## Question

Prepare preliminary estimate of an office building having total carpet area of 3275 m². The area occupied by circulation area is 20% and area occupied by wall is 7%. Assume other data suitably, if needed.
- Plinth area rate of building = Rs. 25,000 per m² (printed as m³)
- Extra for deep foundation = 1.5% of civil cost
- Extra for architectural work = 5% of civil cost
- Extra for water supply work = 6% of civil cost
- Extra for sanitary work = 5% of civil cost
- Extra for electrical works = 8% of civil cost
- Contingencies = 3%
- Supervision charge = 8%

## Short answer

Plinth area = 3275/(1−0.20−0.07) = 4486.30 m². Building cost = 4486.30 × 25000 = Rs 112,157,534.25; adding deep foundation (1.5%), architectural (5%), water supply (6%), sanitary (5%), electrical (8%) yields total building cost Rs 140,757,705.48; with 3% contingency and 8% supervision, total estimate = Rs 156,241,053.08.

## Answer

#### Plinth area
Carpet area is what remains after circulation (20%) and walls (7%) are taken from the plinth area:
$$
\text{Plinth area} = \frac{3275}{1 - 0.20 - 0.07} = \frac{3275}{0.73} = 4,486.30\ \text{m}^2
$$

#### Estimate
Plinth area rate = Rs 25,000 per m² (the paper prints m³, taken as m² because the rate is applied to the plinth area). The extras are taken on the civil cost, as given. The question does not state the basis for contingency and supervision, so they are taken on the total building cost.

| Item | Basis | Amount (Rs) |
|---|---|---|
| Building cost (plinth area x rate) | 4,486.30 m² x 25,000 | 112,157,534.25 |
| Extra for deep foundation | 1.5% of civil cost | 1,682,363.01 |
| Extra for architectural work | 5% of civil cost | 5,607,876.71 |
| Extra for water supply | 6% of civil cost | 6,729,452.05 |
| Extra for sanitary work | 5% of civil cost | 5,607,876.71 |
| Extra for electrical work | 8% of civil cost | 8,972,602.74 |
| **Total building cost** | | **140,757,705.48** |
| Contingencies | 3% of 140,757,705 | 4,222,731.16 |
| Supervision charge | 8% of 140,757,705 | 11,260,616.44 |
| **Total estimated cost** | | **156,241,053.08** |

**Answer: Plinth area = 4,486.30 m²; total estimated cost = Rs 156,241,053.08.**

## Check yourself

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

1. Carpet 3275 m2, circulation 20%, walls 7%. Plinth area is:
   A. 4,486.30 m2
   B. 2,390.75 m2
   C. 3,275 m2
   D. 4,092.50 m2
   Answer: A. 3275/0.73 = 4,486.30. (Key point: Plinth area)

2. The paper prints the plinth area rate as m3. How is it treated?
   A. As per m3 on the volume
   B. As per m2, since it is applied to the plinth area
   C. The rate is ignored
   D. Converted to sq ft
   Answer: B. A plinth area rate is per area. (Key point: Rate unit)

3. Extras 1.5 + 5 + 6 + 5 + 8 percent of civil cost make total building cost equal to civil cost x:
   A. 1.025
   B. 1.11
   C. 1.255
   D. 1.30
   Answer: C. The extras sum to 25.5%. (Key point: Extras)

4. On what are contingency 3% and supervision 8% charged?
   A. The civil cost only
   B. The carpet area
   C. The final total
   D. The total building cost (Rs 140,757,705)
   Answer: D. Total estimated cost is Rs 156,241,053.08. (Key point: Contingency base)

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