__Formation of thumb rules for cement, sand and aggregates__
The purpose of thumb rules is to prepare the rough cost of the
building or plain quantities estimates. You can’t get a perfect quantity with
the thumb rule rather a rough quantity that is almost identical or less to the
accurate quantity.

Definition of thumb rule:
Thumb rule is defined as creating a constant number with previous experience as
well as work experience in the jobsite each day. As for instance, required
covered area is multiplied with thumb rule to obtain rough quantities of the
material.

You can get more clear
ideas on thumb rule on the basis of the following example :-

Assume that 3 different
houses are built up with a covered Area of 1050 square feet each. In every
house various quantities of Cement bags, Sand and Aggregates are utilized for
the construction work. Therefore, a thumb rule is formulated for cement, sand
and aggregates quantity estimations as follow

IN 1ST
HOUSE CONSTRUCTION:

Cement= 600 Bags (as for illustration).

Sand = 2,000 cubic feet.

Aggregates = 1700 cubic feet.

Cement= 600 Bags (as for illustration).

Sand = 2,000 cubic feet.

Aggregates = 1700 cubic feet.

IN 2ND
HOUSE CONSTRUCTION:

Cement = 590 Bags (as for illustration).

Sand = 1900 cubic feet.

Aggregates = 1600 cubic feet.

Cement = 590 Bags (as for illustration).

Sand = 1900 cubic feet.

Aggregates = 1600 cubic feet.

IN 3RD
HOUSE CONSTRUCTION:

Cement = 570 Bags (just for example).

Sand = 1800 cubic feet.

Aggregates = 1500 cubic feet.

Cement = 570 Bags (just for example).

Sand = 1800 cubic feet.

Aggregates = 1500 cubic feet.

How
thumb rule is formed here:-

To form thumb rule for every construction material, the average usage of every particular material should be selected.

To form thumb rule for every construction material, the average usage of every particular material should be selected.

CEMEN:

Average Consumption = (600 + 590 +570)/3

= 586.66 bags.

Average Consumption = (600 + 590 +570)/3

= 586.66 bags.

Now it
is required to determine the quantity of cement that is used in 1 square feet
area.

Covered area = Material consumption.

1050 sft = 586.66 bags.

1sft = (586.66/1050) bags.

1sft = 0.55 bags

Covered area = Material consumption.

1050 sft = 586.66 bags.

1sft = (586.66/1050) bags.

1sft = 0.55 bags

So 0.55 is fundamentally
considered as our cement thumb rule. Now, if it is required to work out the
quantities of cements for 5,000 square feet area (if the conditions are
identical), 0.55 should be multiplied with the covered area to obtain the
cement quantity.

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