Thumb Rules for Civil Engineers

Thumb Rules for Civil Engineers is essential for any civil engineer, Site engineer or civil supervisor. They play a crucial role while taking quick decisions on site. Thumb rules help you in finding out the solution using a simple mathematical formula and make smart decisions whenever needed. But, while using these thumb rules, you must remember that the thumb rule never gives the exact or accurate results, you just have used them for approximate results.

There are numbers of thumb Rules for Civil Engineers which we used in construction work. So, the following are some most frequently used Thumb rules on Construction site.

The Thumb rule method is an approximate & comparing method. In thumb rules and the units are not the same when we compare to get the results. So, ignore units while performing thumb rule.

Thumb rule for estimating the Concrete Volume with respect to the area:

The volume of concrete required = 0.038 m3/square feet area

Example: –

If Plan Area = 40 x 20 = 800 Sq. Ft.

So, for the plan area of 800 Sq. Ft. area the total volume of concrete required

= 800 x 0.038m3 = 30.4m3

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

Steel required in residential buildings = 4.5 Kgs – 4.75 Kgs / Sq. Ft. Steel required For Commercial buildings = 5.0 Kgs-5.50 Kgs/Sq. Ft.

you can also use BN Datta recommendations for the more accurate result:

The following recommendations Thumb Rules for Civil Engineers are given in B N Datta for the Steel quantity used in different members of the building

Percentage of Steel in Structural Members:

1) Slab – 1% of the total volume of concrete

2) Beam – 2% of the total volume of concrete

3) Column – 2.5% of total volume of concrete

4) Footings – 0.8% of the 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

The Total Volume of Concrete for given Slab = 5 x 4 x 0.15

= 3m3

Step 2: Calculate the steel quantity using formula

As per the guidelines are given in B N Dutta reference book the steel quantity of slab is

1% of the total volume of concrete utilized.

Thumb rule to estimate Steel quantity of above slab = Volume of Concrete x Density of

Steel x % of Steel of Member

Steel weight required for above slab = 3 x 7850 x 0.01 = 235Kgs

For accurate estimation, you can refer to Bar Bending Schedule

Thumb Rules for Civil Engineers to estimate the Shuttering area:

Shuttering costs are taken as 15-18% of the total construction of the building. Shuttering work is done to bring the concrete in Shape. The thumb rule to estimate the shuttering required is 6 times the quantity of concrete or 2.4 times of Plinth area.

For example, the concrete quantity is 0.5m3, then

The Shuttering plate Ply, Battens, Nails are components of Shuttering.

Shuttering Ply Quantity estimation:

Suppose 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 shuttering area = 3m

Then Ply required for shuttering = 0.22 x 3 = 0.66m2

Battens Quantity Calculation:

Shuttering battens usually have a length & width of 75mm x 40mm.

Batten Quantity = 19.82 x No. of Ply Sheets

If work requires 25 Ply sheets, the total quantity of Battens is 19.82 x 25 = 495

Battens

Nails & Binding Wire Quantity in Shuttering:

Approximately, 75 grams of Nails used in shuttering of 1m2 area.

75gms of Binding wire is used for every 1m2 of Shuttering. Thumb rule for Shuttering oil estimation:

Shuttering oil is applied on shuttering plate surface used to de-frame or de-assemble from the concrete easily.

Total required Shuttering oil = 0.065 x Total Area of Shuttering

(or)

If, total area of shuttering is 15 m2, then Shuttering oil Consumption = 0.065 x 15 =

0.975.

Building Estimation videos

Thumb rule used for Cement, Sand, Coarse Aggregate Quantity in

Different grades of Concrete:

Note: 1 bag of cement = 50Kgs

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

Thumb Rules for Civil Engineers for Brickwork:

Thumb Rules for Civil Engineers for Cement

Masonry Quantity:

Thumb Rules Plastering Quantity:

Tips for Civil Site Engineers

Some tips for Civil Site Engineers, this tip can prove important when you don’t have any

measurement at site or it is not possible to use them every time.

On-site measurement tricks are important because we do not always have the necessary measurement tools available. Normally, we required take the measurements of

different objects on a daily basis. It is not possible have the measuring tools, such as tape measure, ruler, or protractor, with us.

For that situation, I will give you tricks for measuring different dimensions such as length and degrees.

Let’s, Consider one example if you see your thumb and your index finger, the length between them will be roughly 18 to 19 centimeters.

Similarly, if you open the thumb and the little finger instead, you will get an additional 2 centimeters for a total of about 20 centimeters. This is an important tip for civil site engineers, site engineer for contactor.

But it is fact human hands are different sizes, so this method is just a way to measure the approximate length.

you can see that your thumb and your little finger exactly make 90 degrees, when you spread them on ground.

Calculation F. S. I. of Your House

And if you spree&+ad all other fingers, you can also measure 60 degrees, 45 degrees, and 30 degrees with this method.

Similarly, If you put 4 finger together you can measure distance of 3 ” (inches) or 8

Centimeters approximately.

And if you put 2 fingers together, you can measure distance of 1 1/2″(inches) or 4

centimeters.

Some vital information and formulas for civil engineers

This exclusive construction article is intended for civil engineering students. The article provides some vital information and formulas regarding weight of steel bars per meter, weight of engineering materials, standard conversion factors, concrete grades etc.

Weight of steel bars per meter

          For 6 mm dia bar, the weight will be 0.222 kg

          For 8 mm dia bar, the weight will be 0.395 kg

          For 10 mm dia bar, the weight will be 0.616 kg

          For 12 mm dia bar, the weight will be 0.888 kg

          For 16 mm dia bar, the weight will be 1.578 kg

          For 20 mm dia bar, the weight will be 2.466 kg

          For 25 mm dia bar, the weight will be 3.853 kg

          For 32 mm dia bar, the weight will be 6.313 kg

          For 40 mm dia bar, the weight will be 9.865 kg

The following formula is applied to find out the weight of steel bars: –

W= (D^2 x L)/162

Here, D denotes dia of bars and L denotes total length of steel bars for which the weight should be measured.

As for instance, if it is required to work out the weight of 20 mm steel bars, the calculation will be as follow: –

W = 20^2/162

W = 2.466 kg/meter

A conversion factor stands for a number that is employed to transform one set of units to another, by multiplying or dividing. While doing a conversion, the exact conversion factor to an identical value should be applied. As for instance, to transform inches to feet, the exact conversion value should be

12 inches equivalent to 1 foot.

Given below, the details of standard conversion factors: –

          1 inch = 25.4 mm

          1 foot = 0.3048 m

          1 yard = 0.9144 m

          1 meter = 3.28 ft

          1 mm = 0.0394 inch

          1 mile = 1.6093 km

          1 newton = 0.10 kg

Concrete grades are represented as M10, M20, M30 as per their compressive strength.

The “M” stands for Mix design of concrete succeeded by the compressive strength number in

N/mm2

“Mix” belongs to the relevant ingredient proportions which are Cement: Sand: Aggregate or Cement: Fine Aggregate: Coarse Aggregate.

If  we  refer  to  M15  concrete,  it  signifies  that  the  concrete  contains  15  N/mm2  characteristic compressive strength at 28 days.

For M5 grade of concrete, mix proportion is 1:4:8

For M10 grade of concrete, mix proportion is 1:3:6

For M15 grade of concrete, mix proportion is 1:2:4

For M20 grade of concrete, mix proportion is 1:1.5:3

For M25 grade of concrete, mix proportion is 1:1:2

Given below, the unit weight of various types of engineering materials.

          Bitumen = 1340 kg/m3

          Cement = 1440 kg/m3

          Cast Iron = 7650 kg/m3

          Steel = 7850 kg/m3

          Ice = 913 kg/m3

          Petrol = 690 kg/m3