Estimating and Costing

Detailed estimates are prepared by carefully and
separately calculating in detail the costs of various
items of the work that constitute the whole project
from the detailed working drawings after the design
has been finalized.
Detailed estimates are submitted to the competent
authorities for obtaining technical sanction.

 In Government Organisation, a detailed estimate is required
for obtaining technical sanction from the competent
authorities for the proposed work.
 A detailed estimate is also required for the preparation of
contract (agreement) document.
 The detailed estimates serve as a guide during the execution
of the work.
 It helps in computing the quantities of materials required
and labour to be employed for the completion of various
items of construction.
 It is very useful in the efficient planning and programming of
all activities required for the speedy completion of the work.

 Drawings - Quantities of various items are calculated
on the basis of given drawing
 Specifications - Specification gives description of
material to be used, mode of execution quality of
work etc.The rates are varies according to
specification
 Rates-The rates of various materials used in the
construction and the wages of different categories of
labour should be available for preparing estimate.
 Mode of Measurement - Mode of measurement for
different item of work are taken with reference to IS
1200.

 Taking out quantities
 Squiring
 Abstracting

 The complete work is divided into various
items of work such as earth work concreting,
brick work, R.C.C. Plastering etc.,The details
of measurements are taken from drawings
and entered in respective columns of
prescribed proforma

 The quantities are calculated by multiplying
the values that are in numbers to Depth,
length, width.

 The cost of each item of work is worked out
from the quantities that already computed in
the details measurement form at workable
rate. But the total cost is worked out in the
prescribed form is known as abstract of
estimated form.

Abstract Sheet
Measurement Sheet

 Unit Quantity Method
In the unit quantity method, the work is divided
into as many operations or items as are required.
A unit of measurement is decided.The total
quantity of work under each item is taken out in
the proper unit of measurement.The total cost
per unit quantity of each item is analyzed and
worked out.Then the total cost for the item is
found by multiplying the cost per unit quantity
by the number of units.

 Total Quantity Method
In the total quantity method, an item of work is
divided into the following five subdivisions:
(I) Materials
(II) Labor
(III) Plant
(IV) Overheads
(V) Profit
 The total quantities of each kind or class of material or
labor are found and multiplied by their individual unit
cost. Similarly, the cost of plant, overhead expenses
and profit are determined.

 Long wall Short wall method or PWD method
or in to in and out to out method.
 Centre line method.

 In this method, the wall along the length of room is considered to
be long wall while the wall perpendicular to long wall is said to be
short wall.
 To get the length of longwall or shortwall, calculate first the centre
line lengths of individual walls.Then the length of long wall, (out
to out) may be calculated after adding half breadth at each end to
its centre line length.
 Length of long wall = centre line length of long wll + width of
item
 Thus the length of short wall measured into in and may be found
by deducting half breadth from its centre line length at each end.
 Length of Short wall = centre line length of short wall - width of
item
 The length of long wall usually decreases from earth work to brick
work in super structure while the short wall increases.These
lengths are multiplied by breadth and depth to get quantities.

 This method is suitable for walls of similar cross
sections. Here the total centre line length is multiplied
by breadth and depth of respective item to get the
total quantity at a time.
 When cross walls or partitions or verandah walls join
with main wall, the centre line length gets reduced by
half of breadth for each junction.
 Such junction or joints are studied carefully while
calculating total centre line length.The estimates
prepared by this method are most accurate and quick.
 Length of Item = total centre line length – (1/2 *
Number of junction *width of item)

 Bar Bending Schedule, commonly referred to as
“BBS” is a comprehensive list that describes the
location, mark, type, size, length and number, and
bending details of each bar or fabric in
a Reinforcement Drawing of a Structure.
 This process of listing the location, type and size,
number of and all other details is called “Scheduling”.
In context of Reinforcement bars, it is called bar
scheduling. In short, Bar Bending Schedule is a way of
organizing rebars for each structural unit, giving
detailed reinforcement requirements.

Contingencies :-
 The miscellaneous incidental expenses which
cannot approximately be classified under any
distinct sub head are called as contingencies.
 Some items of work might have been omitted
from the detailed estimate due to oversight or
some miscellaneous items do not form under
any sub head.To meet such expenses, provision
of contingencies is done in detailed estimate.
Normally it is 3 to 5% of estimated cost.

Work charge establishment :-
 The work charge establishment are the
establishment which is directly connected with
work.
 During the construction of a project/work some
supervisory staff such as supervisors, watchman,
store clerk etc. are appointed on temporary
basis.
 To meet this expenditure a provision is made in
the estimate of every work, which is known as
work charged establishment. It is about 2 to 2.5
% of the estimated cost of the work

 Water supply charges :-for the construction if water is
taken from street pipe line 5m from the property line
and to be stored in an overhead tank an amount of 4
to 5 % of estimated cost may be considered in
estimate.
 Electrification Charges:- For electrification wiring and
installation an amount of 8% of the cost of work is
added.
 Sanitary Charges :- An amount of 4 to 5 % of the
estimated cost of work is provided if sewer line is
within 12m from building line.

 Provisional Sum - Provisional sum is an amount
provided in the estimate for some specialized
work to be done by specialist firm.Whose details
are not known at the time of preparing estimate.
The work like installation of A.C, Lift etc. are
comes under provisional sum whose full
information and details may not be known at the
time of preparing estimate.The amount paid to
the contractor will not necessarily be the exact
amount of provisional sum.

 Prime cost :- Prime Cost is the net cost or purchase cost of articles
at shop and refers to the supply of articles only and not to the
carrying out of work. It is not always possible at the time of
preparing estimate to specify the exact requirement of articles
such as water supply fittings, sanitary fittings,door &window etc.
The same has to be decided while actual fitting of articles, for the
execution of such item a reasonable amount is kept in estimate as
Prime Cost.The price paid to the contractor for prime cost article
will be the actual cost paid by him, he is not allowed to take some
profit on that material.
 Provisional Quantity :- When the quantities of particular items
are uncertain due to unavailability of data, provisional quantities
of those items are called provisional items and corresponding
quantities are called provisional quantities.

 Day work :- The procedure of costing or
valuing an item of work on the basis of actual
labors and materials required, is called day
work.This method is used in certain items
where it is difficult to take measurement for
e.g Architectural elevation of building,
preparation of statue and under water
construction etc. Contractor have to maintain
the record of daily consummation of material
and labour engaged.

Estimating and Costing

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