# Thumb Rules Used In Construction – Civil Engineering

Contents

## What Is Thumb Rule?

Thumb rule is an approximate method for doing something. This particular method is based on the practicality of an activity rather than its theory, that’s why it is known as an approximate method. This method is not accurate. It provides the results or the values approximately, but nearer to its perfect result.

Thumb rule is a method on which one cannot rely in every situation due to its lesser accuracy relatively, but still, it is used widely on construction sites as it seems easier to engineers.

One of the advantages of using thumb rules is that one can get on a spot solution for a particular activity or a problem. It gives some really quick answers to the questions arising on site, making the work a lot easier for the engineers and site in charge.

Let us learn about some of the thumb rules which are frequently and popularly used by engineers on site.

### Quantity Of Steel Used In Beam, Column, Slab & Footing:

Quantity of steel for,

• Residential structure = 4.5 kg to 4.75 kg per square feet.
• Commercial structure = 5 kg to 5.50 kg per square feet.

Quantity Of Steel In Different Structural Members

• Slab = 1 % of total volume of concrete in slab.
• Beam = 2 % of total volume of concrete in beam.
• Footings = 0.8 % of total volume of concrete in footings.
• Column = 2.5 % of total volume of concrete in column.

Let’s take an example of a slab and calculate the quantity of steel in the slab of size = 8m x 6m x 0.15m

The quantity of steel in a slab is 1 % of total volume of concrete. So we need to calculate the quantity of concrete in this slab.

Total quantity of concrete = 8 x 6 x 0.15 = 7.2 m3.

Now, calculating the quantity of steel = total volume of concrete x density of steel x 0.01

• = 7.2m3 x 7850 kg/m3 x 0.01
• = 565.2 kg.

The total quantity of steel required in the given slab is 565.2 kg.

Similarly for other structural components, the quantity of steel can be worked out.

Note – it is found that for 1000 kg of steel (1000 kg = 1 ton), 7 kg to 13 kg of binding wire is used. This is an approximation hence the variation is there in the quantity of it.

### Quantity Of Concrete With Respect To Area

For 1 square feet of area, an approximate quantity of 0.038 m3 of concrete is taken.

For example, if the plan area is 1500 square feet, the quantity of concrete is calculated as follows:

• Area = 1500 square feet
• Quantity of concrete per square feet = 0.038 m3

Total quantity of concrete required = 1500 x 0.038

= 57 m3.

### Quantity Of Shuttering (Formwork) And Its Components

#### Shuttering Area:

It is taken as 6 times the total quantity of concrete or 2.4 times the area of the plinth. Suppose the quantity of concrete is 10 m3, then the area of shuttering is,

• 6 x 10 = 60 m2.

#### Quantity Of Shuttering Ply:

Quantity of shuttering ply is calculated by multiplying the area of shuttering by 0.22.

For example, if the area of shuttering is 5 m2, then the quantity of shuttering ply required is,

• 0.22 x 5 = 1.1 m2

#### Quantity Of Battens:

When the number of ply sheets is multiplied with 19.82, we get the total quantity of battens. For example,

If there are 50 ply sheets, then the quantity of batten is calculated as follows:

• 50 x 19.82 = 991 battens.

#### Quantity Of Shuttering Oil:

The quantity of shuttering oil required can be considered in two ways. They are,

0.065 times of the total area of shuttering Or

1 litre of oil is consumed for 15 m2 of shuttering area. For example, if the area of shuttering is 20 m2 then, 20/15 = 1.33 litres of shuttering oil is required.

#### Quantity Of Nails And Binding Wire:

An approximate quantity of 75 grams of nails is required for every 1 m2 of shuttering area and similarly, 75 grams of binding wire is approximately required for every 1 m2 of shuttering area.

### Quantity Of Cement, Sand, Aggregates In Different Concrete Grades

Note – 1 bag of cement weighs 50 kg.

### Labour Productivity For Different Construction Activities

Labour productivity is measured for work done for 8 hours per day, by a single person or a pair of labours.

### 6 thoughts on “Thumb Rules Used In Construction – Civil Engineering”

1. Very informative. It is the Juice of Construction Engineering.

2. Love it…..