We can’t calculate each and everything in the field.

Sometimes we have to act quickly to move on. Every professional have maintained their own set of thumb rules. 

What is Thumb Rule?

Rule of thumb

At first, we have to understand the meaning of thumb rule before jumping into the discussion.

  • Thumb rules are “ Approximate Value”.  
  • Thumb Rules has no unit systems

We use the thumb rules for almost in every calculation like concrete calculation, manpower estimation, the material requirement for plastering, wastage’s calculation, brickwork calculation, etc.,

For example, 

What is the requirement of bricks for 1 Cum? As per the calculation 625 nos.

But we Say Approx 600 nos. It is called as a thumb rule. Because we can not estimate every time according to the individual requirement.

Thumb rule for Manpower Productivity Estimation

Manpower productivity thumb rules will be useful to calculate the total manpower required for your next schedule.

SI Manpower  Activity Output – 8 Hours
1 Mason – 1
Male mazdoor – 0.75
Female Mazdoor – 0.5
Brick Work 45 Cft
2 Mason – 1
Male mazdoor – 1
Female Mazdoor – 0.5
Wall plastering 120 Sft
3 Mason – 1
Male mazdoor – 0.75
Female Mazdoor – 0.5
Ceiling Plastering 90 Sft
4 Carpenter-2.25
Foreman- 0.2
Helper- 2.25
Shuttering Work 11 Sqm
5 Bar Bender – 1 Nos
Helper – 1 Nos
Steel Work 100 Kg
6 Tile Mason – 1 Nos
Helper – 1 Nos
Tile Work 10 Sqm
7 Mason – 2
Male mazdoor – 1.75
Female Mazdoor – 1.75
Block Work 2 Cum
8 Male Coolie – 5 Nos
Female Coolie – 4 Nos
Earth Digging 1000 Cft

Thumb rule for concrete work

The concrete ingredients will be vary based on the mix ratio.

For Example, 

If the Plinth area is 100 Sq.ft (10 x 10) and the required concrete volume is 100 x 0.04 = 4 Cum with M5 mix ratio means

Now from the below table which is for 1 m3

Required Concrete ingredients for 4 m3 of M5 is

Cement – 2.77 x 4 = 11.08 bags

Sand – 0.48 x 4 = 1.92 cum

Coarse aggregate = 0.96 x 4 =  3.84 cum

Thumb Rule of Concrete material requirement

Grade Ratio Cement in Bags Sand in Cum Coarse Aggregates in Cum
M5 01:05:10 2.77 0.48 0.96
M7.5 01:04:08 3.41 0.047 0.95
M10 01:03:06 4.44 0.46 0.92
M15 01:02:04 6.34 0.44 0.88
M20 01:05.5 8.06 0.42 0.84
M25 01:01:02 11.09 0.39 0.77

Must Read:- What is water cement Ratio

Thumb rule for Plastering Work

For plastering, the material quantity will vary based on the different mix ratio like concrete and the thumb rule for plastering work has listed below.

Type of Plastering Mix ratio Thickness in mm Cement Bags/Sqm Sand  Cum/Sqm
Inner Plastering 1:3 15 0.16 0.017
External Plastering 1:4 20 0.17 0.024
Rough Plastering 1:5 16 0.11 0.020
Ceiling Plastering 1:2 12 0.17 0.012

To know more How to calculate material for Plastering work

Thumb rule for Brick Work

The size of brick 190mm x 90mm x 90mm

Number of bricks per cum = 500 Nos

Must read: How to calculate the number of bricks 

Mix Ratio and brickwork thickness Mortar Thickness in mm Cement in Bags Sand in Cum
1:6 200mm Thk 10 1.4 / Cum 0.30
1:5 200mm Thk 10 1.7 / Cum 0.25
1:4 100mm Thk 10 0.15 / Sqm 0.035
1:5 200mm Thk Block 10 0.15 / Cum 0.02

Thumb rule for Steel in RCC

The steel cost very expensive compared to other construction material and the excess purchase of steel requirement impact the project budget. A good designer restrains steel utilization. 

Type of Structure Steel Kg/Sft
Residential Building 2.5 to 4.5
Commercial Building 4.5 to 5.5
Mass Project Tall or heavy Structure 6 to 8

The steel percentage against concrete volume will vary based on the structural element and the minimum and maximum percentage of steel utilization have listed below as per IS standard.

The Thumb rule for steel in RCC has listed below.

Structural Element Percentage of Steel in Concrete
Slab 1%
Beam 1% to 2%
Column 2.50%

Must Read: How to calculate steel weight for Reinforcement

Example calculation:

Steel quantity = Volume of Concrete x Density of Steel x % of Steel.

For example, if a volume of concrete 1 cum for a slab.

Approx Steel requirement = 1 x 7850 x 1% = 78.5 Kg/Cum.

Read: Bar bending Shape codes

Thumb rule for shuttering work

The shuttering work is called by another name “Form Work” because it gives a uniform shape and smoothness for the concrete. Generally, it takes 10% to 15% of the cost of the total budget.

The Thumb rule for shuttering work is listed below.

Type of Concrete Element No of Times Sqm Per Cum
Foundation 2 to 3 times of concrete volume
Column 11 to 13 times of concrete volume
Beam 11 to 12 times of concrete volume
Slab 6 to 8 times of concrete volume

For example, if the slab concrete volume 1 cum then the approx shuttering requirement is 1 x 6 = 6 Sqm.

If we have missed anything please do let us know to update! 

Do you have any kind of thumb rules for yourself? If so share it with us in the comment section we would like to also learn something from you.

Author

Satheesh is a Civil Engineer who has more than 9+ Years of experience in residential construction. He is the author, editor of Civil Planets

3 Comments

Write A Comment

error: Content is protected !!