Thumb rules refers to an easily learned process or standard based on practical experience rather than theory. It is not intended to be strictly accurate or reliable for every situation.Thumb rules give us the quick decisions at construction field. It provides with the rules of mathematical formula and broad ideas whenever needed. As a engineer, we have to be practical and quick in the field of construction. Basically,thumb rule is the guide for civil engineers for predictable results. It can vary to some percent but it will give a general idea as well.When we compare to get the result, the units in the thumb rules are not the same. Therefore, never consider units when performing the thumb rule.There are several thumb rules that we apply in construction. Here I am discussing the most frequently used thumb rules on the site.

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

The Concrete Volume of 0.038 m3 of concrete is used for each Square Feet of Plan area.

Example:-

Lets consider ,  Plan Area = 45 x 25 =1125SFT

Building plan area

The plan area is 1125 SFT then the total volume of concrete required = 1125 x 0.038 m3 = 42.75 m3

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

For Residential buildings   -  4.5Kgs - 4.75 Kgs /SFT

For Commercial buildings  -  5.0Kgs - 5.50 Kgs/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.

Examples:

FOR SLAB:

How to calculate the steel quantity of slab having the Length, width, and depth of the slab is 6m x 5m x 0.15m

Step 1: Calculate the Volume of Concrete

Total Volume of Concrete for above given Slab is 6 x 5 x 0.15 = 4.5 m3

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 = 4.5 x 7850 x 0.01 = 353 Kgs

FOR COLUMN:

How to calculate the steel quantity of column having the Length, width, and height of the slab is 1.2m x 0.3m x 4.2 m

Step 1: Calculate the Volume of Concrete

Total Volume of Concrete for above given column is 1.2 x 0.3 x 4.2 = 1.512 m3

Step 2: Calculate the steel quantity using formula

As per the above table, the steel quantity of column is 2.5% 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 = 1.512 x 7850 x 0.025 = 297 Kgs

Similarly , you can calculate for Beam and Footings.

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 and giving a desired mould in terms of quality.

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 0.8 m3, then the shuttering area required is  0.8 x 6 = 4.8 m2

Components of Shuttering:-

Components of Shuttering are shuttering ply, battens and nails.

Shuttering Ply Quantity calculation:

The shuttering Ply has a length, width & depth of 2.45 x 1.22 x 0.012

The No. of Shuttering Ply sheets = 0.22 times of Shuttering

Suppose, the area of shuttering required = 4.8 m2

Then the Shuttering Ply required = 0.22 x 4.8 = 1.056 m2

Battens Quantity Calculation:

Battens have different widths but we usually use shuttering batten having a length & width of 75mm x 40mm.

Batten Quantity = 19.82 x No. of Ply Sheets

if the construction requires 32 Ply sheets, the total quantity of Battens are 19.82 x 32 = 634 Battens

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 15 m2 of shuttering 1 litre of shuttering oil is consumed.

Example :

15m2is total area of shuttering,  then Shuttering oil required = 0.065 x 15 = 0.975 litres

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.

Example:

15m2 is total area of shuttering,  then Binding wire  required = 75 x 15 = 1125gms