Home Tips & Tricks - How To's Civil Engineering Thumb Rules ? Common Must Know Construction Rules

# Civil Engineering Thumb Rules ? Common Must Know Construction Rules

Any site supervisor, hands-on contractor, or civil engineer must know about some basic engineering laws and formula that are used every day in most building situation. As a civil engineer, you are expected to know and remember these civil engineering thumb rules. Today, we will look into what are the common rules a civil engineer must know.

## What are Civil Engineering Thumb Rules

The common rules, or thumb rules are some simple mathematical formula that help you to find out the solution to a given problem. In construction, they are extremely important for intelligent and informed decision making on the go. They are easy to use and much of the calculation using these can be done in your head, or in a pocket calculator or mobile calculator.

While the civil engineering thumb rules are very handy, there is a downside to them as well. These rules and formulas are good for doing approximated work only; to make snap decision on the moment. But they are also inaccurate! When the time comes to do the actual work, you had better use the textbook formulas, official tables, or charts.

If you are working in the field, there are quite a few civil engineering mobile apps that can help you with the fieldwork calculations-consider them a digital upgrade to the civil engineering thumb rules. Anyway, let us move forward to see what are the most common thumb rules for site engineers.

### A. Estimating concrete volume in an area

• Volume of concrete per unit area = 0.038 m3/ft2

### B. Estimating steel quantity for load-bearing members

• For residential buildings: 4.5 to 4.75 kg/ft2
• For commercial buildings: 5 to 5.5 kg/ft2

These rules are good for calculating reinforcement amounts in beams, columns, slabs, and footings.

### C. Percentage of steel in structural members:

With respect to total volume of concrete in a given structural member,

• Steel required in a slab: 1%
• Steel required in a beam: 2%
• Steel required in a column: 2.5%
• Steel required in a footing: 0.8%

### D. Estimation of Shuttering:

1. Total area of shuttering = 6 x concrete volume, or, 2.4 x plinth area
2. Shuttering ply quantity = 0.22 times the shuttering area. Then divide it by the area of each ply sheet to get the number of ply sheets or boards required.
3. Shuttering battens quantity = 19.82 x no. of ply sheets
4. Nails quantity in shuttering = 75 grams/m2 shuttering area
5. Binding wire quantity in shuttering = 75 grams/m2 of shuttering
6. Shuttering oil quantity = 0.065 x shuttering area. Or, 1 liter/15 m2 of shuttering area.

## L-type Columns

Very rarely found, these columns are suitable in the very isolated cases of being in the corners of tall boundary walls needing extra support. L-type columns have similar properties as rectangular columns, and are just as easy and cheap to cast. However, due to the rare need, it’s hard to find them in use.

## T-type Columns

Most commonly found holding up bridges, flyovers, and similar heavy elevated paths, they are favored in heavy construction and are made to be very strong, since they have to bear all the load of the section alone. They are also easily cast, like rectangular columns, and are cheap, considering the situational requirements.

## V-type Columns

Another rare type, the column is cast in a V shape only if the room is trapezoidal or triangular in shape, which is quite uncommon, indeed. It is not cheap to cast due to the odd shape of formwork needed, and the excess amount of concrete needed- it requires the most amount of concrete per cross sectional area among all types of columns.

1. Cement required for 1 m3 brickwork =
• o 0.876 m3 for 230 mm brickwork
• o 0.218 m3 for 115 mm brickwork
2. Cement required for 1 m2 masonry =
• o 6.2 kg for 200 mm 1:6 work
• o 4.65 kg for 150 mm 1:6 work
• o 10.3 kg for 200 mm 1:4 work
• o 7.2 kg for 150 mm 1:4 work
• o 5.15 kg for 100 mm 1:4 work
3. Cement required for 1 m2 plastering:
• o 4.5 kg for rough plastering, internal wall, and ducts
• o 8.75 kg for external walls and stucco plastering
• o 25.5 kg for lath plastering

Note: for the cement quantity estimation, find the mass of cement required in kg first, and then to find out the number of cement bags required, used this thumb rule: 1 bag of cement = 50 kg.

## Wrapping up

The above rules were the common civil engineering thumb rules you must know if you are a civil engineer or site engineer or supervisor. These thumb rules of civil engineering will help you figure out material quantities quickly and that will let you make snap decisions on the field.

We hope this article about common rules that a site engineer should remember has been useful to you. Please let us know what you think using the comments section below. We are eager to hear your thoughts and suggestions!