# Important Thumb Rules used in Construction by Civil Engineers

Thumb rules play a most crucial role while taking quick decisions on site. Thumb rules enable you to calculate the solution using a simple mathematical formula and make smart decisions whenever needed. Remember, thumb rules never give the accurate results, but you can use them for approximate results. There are many thumb rules which we apply in construction. Here I am discussing the most frequently used Thumb rules on site.
Thumb rule is an approximate & comparing method. In thumb rules, The units are not the same when we compare to get the results. So never consider units while performing thumb rule.

## Thumb rule to calculate the Concrete Volume with respect to area:

The Concrete Volume of 0.038mof concrete is used for each Square Feet of Plan area
Example:-
From below fig: Plan Area = 40 x 20 = 80SFT
The plan area is 80SFT then the total volume of concrete required = 800 x 0.038m3 =30.4m3

## Thumb rule to calculate the Steel quantity required for Slab, Beams, Footings & Columns:

For Residential buildings 4.5Kgs-4.75Kgs /SFT
For Commercial buildings 5.0Kgs-5.50Kgs/SFT
For more accurate results you can also use BN Datta recommendations:
As per B N Datta, the Steel quantity used in different members of the building can be calculated easily using the following recommendations.
Structural Member Percentage of Steel
Slab 1% of total volume of concrete
Beam 2% of of total volume of concrete
Column 2.5% of total volume of concrete
Footings 0.8% of total volume of concrete
Example:
How to calculate the steel quantity of slab having the Length, width, and depth of the slab is 5m x 4m x 0.15m
Step 1: Calculate the Volume of Concrete
Total Volume of Concrete for above given Slab is 5 x 4 x 0.15 = 3m3
Step 2: Calculate the steel quantity using formula
As per the above table, the steel quantity of slab is 1% of the total volume of concrete utilized.
Thumb rule to calculate Steel quantity of above slab = Volume of Concrete  x Density of Steel x % of Steel of Member
Steel quantity required for above slab = 3 x 7850 x 0.01 = 235Kgs
For accurate calculation, you can refer to Bar Bending Schedule

## Thumb rule to calculate the Shuttering area:

Shuttering costs 15-18% of the total construction of the building. Shuttering is framed to bring the concrete in Shape. Thumb rule to calculate the shuttering required is 6 times the quantity of concrete or 2.4 times of Plinth area.
Suppose, the concrete quantity is 0.5m3 then the shuttering area required is  0.5 x 6 = 3m2
Components of Shuttering:-
Shuttering Ply, Battens, Nails are components of Shuttering.

### Shuttering Ply Quantity calculation:

The shuttering Ply has a length, width & depth of 2.44 x 1.22 x 0.012
The No. of Shuttering Ply sheets = 0.22 times of Shuttering
Suppose, the area of shuttering required = 3m
Then the Shuttering Ply required = 0.22 x 3 = 0.66m2

### Battens Quantity Calculation:

Shuttering batten usually have a length & width of 75mm x 40mm.
Batten Quantity = 19.82 x No. of Ply Sheets
if the construction requires 25 Ply sheets, the total quantity of Battens are 19.82 x 25 = 495 Battens

### Nails & Binding Wire Quantity in Shuttering:

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

### Thumb rule for Shuttering oil Quantity:

Shuttering oil is used to de-frame or de-assemble from the concrete easily.
Total required Shuttering oil is = 0.065 x Total Area of Shuttering
(or)
For every 15m2 of shuttering 1 litre of shuttering oil is consumed.
Example :
15m2 is total area of shuttering,  then Shuttering oil required = 0.065 x 15 = 0.975 lts
For Accurate Shuttering Area Calculation, You can check here Shuttering area required for slabs, columns, Beams, Footings

## Thumb rule for Cement, Sand, Coarse Aggregate Quantity in Different grades of Concrete :

Concrete Mix Cement Quantity Coarse Aggregate Quantity Fine Aggregate Quantity
M5 (1:5:10) 2.82 Bags 0.98m3 0.49m3
M7.5(1:4:8) 3.48 Bags 0.97m3 0.48m3
M10(1:3:6) 4.50 Bags 0.90m3 0.45m3
M15(1:2:4) 6.60 Bags 0.88m3 0.44m3
M20(1:1.5:3) 8.40 Bags 0.84m3 0.42m3
Note: 1 bag of cement = 50Kgs
For Accurate calculation refer to Concrete Mix design for Different grades of concrete

## Brickwork Thumb rule:

Brickwork for 1m3 Cement Qty
in m3
Cement Qty
in Bags
230 mm Brickwork 0.876m3 25.4 Bags
115 mm Brickwork 0.218m3 6.32 Bags

## Cement Masonry Quantity Thumb Rule:

Cement Masonry Type & Mix Cement Qty in Bags Cement Qty in Kgs
200mm in Cement Masonry work of ratio 1:6 0.124Bags/m2 6.2Kgs/m2
150mm in Cement Masonry work of ratio 1:6 0.093Bags/m2 4.65Kgs/m2
200mm in Cement Masonry work of ratio 1:4 0.206Bags/m2 10.3Kgs/m2
150mm in Cement Masonry work of ratio 1:4 0.144Bags/m2 7.2Kgs/m2
100mm in Cement Masonry work of ratio 1:4 0.103Bags/m2 5.15Kgs/m2

## Plastering Quantity Thumb Rule:

Type of Plastering Cement Qty in Bags Cement Qty in Kgs
Rough Plastering 0.09Bags/m2 4.5Kgs/m2
Internal Wall Plastering 0.09Bags/m2 4.5Kgs/m2
Duct Plastering 0.09Bags/m2 4.5Kgs/m2
External Wall plastering 0.175Bags/m2 8.75Kgs/m2
Stucco Plastering 0.175Bags/m2 8.75Kgs/m2
Lathen Plastering 0.55Bags/m2 27.5Kgs/m2