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 0.038m³ of concrete is used for each Square Feet of Plan area

Example:-

From below fig: Plan Area = 40 x 20 = 800SFT

The plan area is 800SFT then the total volume of concrete required = 800 x 0.038m³ = 30.4m³

You can learn more about Concrete Volume calculation 

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.

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 :

Note: 1 bag of cement = 50Kgs

For Accurate calculation refer to Concrete Mix design for Different grades of concrete

Thumb rule for Cement quantity in Brickwork, Cement Masonry & Plastering work in construction:

Brickwork Thumb rule:

Cement Masonry Quantity Thumb Rule:

Plastering Quantity Thumb Rule:

Also Read:- 

Accurate Shuttering Area Calculation

Concrete Mix Design

Bar Bending Schedule

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