ESTIMATION BASIC CONCEPTS
ESTIMATION
DEFINITION OF ESTIMATION:-
“Estimate
may be defined as the process of calculating the quantities and cost of the
various items required in connection with work”
Or
“Estimate
is prepared by calculating the quantities, from the dimensions on the drawings
for the various items required to complete the project and multiplied by unit
cost of the item concerned .To prepare an estimate ,drawings consisting of the
plan , the elevation and the sections , along with the detailed specifications
, properties and proportion of material are required.
2.1.2
PURPOSE
OF ESTIMATING:-
Estimate
for a work or project is necessary mainly for the following purposes :-
a) To
ascertain the necessary amount of money required by the owner to complete the
proposed work .
b) To
calculate the number of different categories of workers that are to be employed
to complete the work within the scheduled time of completion.
c) To
assess the requirements of tools , plants and equipments required to complete
the work according to the programme.
d) To
fix up the completion period from the volume of works involved in the estimate.
e) To
invite tenders and prepare bills for payment.
2.1.3
TYPES
OF ESTIMATES:-
There are different types of estimates and
they are as follows :-
Detailed Estimate
This includes the
detailed particulars for the quantities , rates and costs of all the items
involved for satisfactory completion of a project.
Preliminary or Approximate or Rough
Estimate
This is an
approximate estimate to find out an approximate cost in a short time and thus
enables the authority concerned to consider the financial aspect of the scheme.
Such an estimate is framed after knowing the rate of similar works and from practical knowledge in various ways for
various types of works such as :
a) Plinth
area or square metre method
b) Cube
rate or cubic metre method
c) Service
unit or unit rate method
d) Bay
method
e) Approximate
quantities with bill method
f) Cost
comparison method
g) Cost
from materials and labour
2.1.4
QUANTITY ESTIMATE
AND QUANTITY SURVEY:- This is a complete estimate
or list of quantities for all items of work required to complete the concerned
project.
2.1.5
REVISED ESTIMATE:- A revised estimate is a detailed estimate for the revised
quantities and rates of items of works originally provided in the estimate without material
deviations of a structural nature from the probable variations for quantity, rate
and amount for each item of work of the project.
2.1.6
SUPPLEMENTARY
ESTIMATE:- While a work is in progress some changes
or additional works due to material deviation of a structural nature from the
design originally approved may be thought necessary for supplementary estimate.
2.1.7
COMPLETE ESTIMATE:-
This is an estimated cost of all items which are
related to the work in addition to the main contract or to the “ detailed
estimate “
2.1.8
ANNUAL
MAINTENANCE OR REPAIR ESTIMATE:- After completion
of a work it is necessary to maintain the same for it’s proper function and for
the same, an estimate is prepared for the items which require renewal ,
replacement etc. in the form of a detailed estimate .
2.1.9
PREPRATION OF
DETAILED ESTIMATE:- The unit quantity method
is followed to prepare a detailed
estimate in this method rates per unit work of the including profit are
considered first and the total cost for the item is found by multiplying the
cost per unit of the rate by the number of units.
The
procedure for the prepration of a detailed estimate is divided into two parts
Details of measurement and calculations of
quantities:- It is the first part respective measurements for dimensions of all
individuals items involved in the whole work are taken off from the drawing of
the work.
Table 2.1.1
Measurement Form
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S.No.
|
Items
of Work
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Nos
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Length
(m)
|
Width
(m)
|
Height
(m)
|
Quantity
|
Unit
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Remarks
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Abstract of estimated cost:-It is the second part in the preparation of detailed estimate .
The
cost of each and every individual item of work is calculated by multiplying the
quantity computed in the Measurement Form with the specified rate in a tabular
form known as ‘Abstract Form’.
Table 2.1.2 Abstract of Estimate Form
|
S.No.
|
Description
or particulars
|
Quantity
|
Unit
|
Rate
Rs. P.
|
Unit
of rate
|
Amount
Rs. P.
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