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.
Table of Contents
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
You may also read: