Home > Civil > Important Thumb Rules used in Construction by Civil Engineers

# Important Thumb Rules used in Construction by Civil Engineers

## Important Thumb Rules used in Construction by Civil Engineers

Thumb rule play very important rule while taking quick decision on site. With the help of thumb rules, you can solve the solution very quickly and by using simple mathematical formula. It can’t give you the accurate value but it can give approximate value. There are a lot of thumb rules used in construction by civil engineers. While performing thumb rule, the units are not always same, so never consider units in thumb rules.

There are a lot of thumb rule’s charts used on construction site but few of the thumb rules are used in construction by civil engineers. Following are some of these charts given with an example;

### Thumb Rule for Cement, Sand, Coarse Aggregate Quantity in Different Grades of Concrete

You can easily calculate the quantity of cement, sand, coarse aggregate for specific grades of concrete using the following chart.

 S. No Grade of Concrete Cement (Bags) Sand (m3) Coarse aggregate (m3) 1 M5 (1:5:10) 2.82 0.49 0.98 2 M7.5(1:4:8) 3.48 0.48 0.97 3 M10(1:3:6) 4.50 0.45 0.90 4 M15(1:2:4) 6.60 0.44 0.88 5 M20(1:1.5:3) 8.40 0.42 0.84

Must Read: What is water cement Ratio

Example:

To find the materials for M5 grade of concrete we will take an example for better understanding;

Let, the volume (of the slab) is 10 m3

First we will find the quantity of cement

Cement = volume x 2.82 (table value)

Cement = 10 x 2.82

Cement = 28.2 bags

Now, we will find the quantity of sand

Sand = volume x 0.49 (table value)

Sand = 10 x 0.49

Sand = 49 m3

Now, we will find the quantity of coarse aggregate

Coarse aggregate = volume x 0.98 (table value)

Coarse aggregate = 10 x 0.98

Coarse aggregate = 98 m3

### Thumb Rule for Steel in RCC (Reinforcement Concrete)

The steel is very expensive than the other construction materials. It is very expensive to purchase excessive steel because purchase of extra steel will impact the budget of project very badly. There are some thumb rule charts to find steel in reinforcement concrete (RCC) structures that is given.

#### Thumb Rule for Steel in RCC Structures

 S. No Type of structure Steel ( Kg/ft2 ) 1 Residential Building 2.5 – 4.5 2 Commercial Building 4.5 – 5.5 3 Heavy Structure 6 – 8

Example:

Let’s take an example to find steel for residential buildings

Area of residential building is 100 m2

Steel in residential building = volume x 2.5 (table value)

Steel in residential building = 100 x 2.5

Steel in residential building = 25 kg

#### Thumb Rule for Steel in RCC Members

 S. No Structural members Percent of steel (%) 1 Slab 1 % 2 Beam 1 – 2% 3 Column 2.5 %

Example:

To find the steel in structural members such as slab, beam and column the steps are given:

In this example, we will find the steel for slab. The volume of concrete in slab is 100 m3

Step 1:

Steel quantity of slab = Volume of Concrete x Density of Steel x % of Steel of Member

Steel quantity of slab = 100 x 7850 x 1%

Steel quantity of slab = 7850 kgs

### Thumb Rule for Masonry Work

Masonry work include bricks, mortar and plaster. The composition of mortar and plaster is cement and sand. There are different thumb rules used for plaster materials and mortar materials

#### Thumb Rule for No. of Bricks

No. of bricks = 500 per cubic meter

Example:

To find the brick let’s take an example for better understanding suppose the volume of wall is 10 m3

No. of bricks = Volume of wall x 500

No. of bricks = 10 x 500

No. of bricks = 5000

#### Thumb Rule for Plastering Work

The following is the chart used for calculation of plastering material (cement & sand) for different types plastering work.

 S. No Type of plastering Ratio Thickness of plastering (mm) Cement (bags) Sand (m3) 1 Inner 1:3 15 0.16 0.017 2 External 1:4 20 0.17 0.024 3 Rough 1:5 16 0.11 0.020 4 Ceiling 1:2 12 0.17 0.012

Example:

To find the plastering materials, let’s take an example for better understanding. Suppose the area of wall is 10 m2

Finding the materials for inner plastering first step is to find cement

Calculation of Cement

cement = Area x 0.16 (table value)

cement = 10 x 0.16

cement = 1.6 bags

Calculation of Sand

sand = Area x 0.017 (table value)

sand = 10 x 0.017

sand = 0.17 m3

#### Thumb Rule for Mortar Work

This chart provides values used for the calculation of mortar materials for various mix ratios;

 S. No Mix Ratio Cement (bags) Sand (ft3) 1 1:3 0.06 0.225 2 1:4 0.047 0.24 3 1:5 0.04 0.25 4 1:6 0.03 0.26 5 1:8 0.026 0.27 6 1:10 0.020 0.275

Example:

To find the mortar materials, let’s take an example for better understanding. Suppose the volume of wall is 100 ft3. Find the materials for 1:3 mix design.

The first step is to find quantity of cement

Calculation for Cement

Cement = Volume x 0.06 (table value)

Cement = 100 x 0.06

Cement = 6 bags

Calculation of Sand

Sand = volume x 0.225 (table value)

Sand = 100 x 0.225

Sand = 22.5 ft3

### Thumb Rule for Shuttering

There are different components in shuttering and different thumb rules that is used in shuttering is given below

#### Thumb Rule for Shuttering Oil

The following equation is used for the calculation of shuttering oil for a specific area.

Total Shuttering oil is required = 0.065 x Total Area of Shuttering (m2)

Example:

To find the shuttering oil, let’s take an example for better understanding. Suppose the area of shuttering is 100 m2.

Shuttering oil = Area x 0.065

Shuttering oil = 100 x 0.065

Shuttering oil = 6.5 liter

#### Thumb Rule for Shuttering Removal

The following chart provides the details about shuttering removal after a specific duration for different structures.

 S. No Members of structure Days 1 Sides of foundation, beam, columns and walls 2 days 2 Sides of slab under 4.5 meter span 7 days 3 Sides of slab above 4.5 meter span 14 days 4 Side of beams and arches up to 6 meter span 14 days 5 Side of beams between 6 meter to 9 meter span 21 days 6 Side of beams and arches above 9 met 28 days

#### Thumb Rule for Shuttering Nails & Binding Wire

The following quantity of nails & binding wire is used in shuttering per unit area.

75gms of Nails are used for 1m2 of Shuttering

75gms of Binding wire is consumed for every 1m2 of Shuttering.

Example:

To find the shuttering nails or binding wire, let’s take an example for better understanding. Suppose the area of shuttering is 100 m2.

Shuttering Nails = Area x 75

Shuttering Nails = 100 x 75

Shuttering Nails = 750 gms

Calculation for binding wire used in shuttering

Shuttering binding wire = Area x 75

Shuttering binding wire = 100 x 75

Shuttering binding wire = 750 gms

#### Shuttering Ply Quantity Calculation:

The quantity of shuttering ply can be calculated using the following equation.

No. of Shuttering Ply sheets = 0.22 times of Shuttering (m2)

Example:

To find the shuttering ply quantity, let’s take an example for better understanding. Suppose the area of shuttering is 100 m2

No. of shuttering ply sheets = (Area x 0.22) / Area of ply sheet

No. of shuttering ply sheets = 100 x 0.22 / Area of ply sheet

No. of shuttering ply sheets = 22 / Area of ply sheet

#### Battens Quantity Calculation:

The number of batten quantity can be calculated using the following equation

Batten Quantity = 19.82 x No. of Ply Sheets

Example:

To find the shuttering batten quantity, let’s take an example for better understanding suppose the number of shuttering ply sheets is 10.

Batten Quantity = No. of Ply Sheets x 19.82

Batten Quantity =10 x 19.82

Batten Quantity =198.2 Nos