Brief introduction about estimates and its types

1. Introduction to Estimation
TAPI DIPLOMA ENGINEERING COLLEGE

2. ESTIMATION
Estimation or estimating is the process of calculating the
quantitiesof various itemsof works involved in theproject.
Costing : It is the process of
determining the probable cost
of the project after Knowing
the quantities of various items
and their unit rate is called
costing
ESTIMATION
Estimation or estimating is the process of calculating the
quantities of various items of works involved in the project.

3. ESTIMATE
Estimate is a process of calculating the quantities and costs of the
variousitemsrequired inconnectionwiththework.
Quantity Surveying :
It is the process of calculating
the quantities of various
items of work for any
construction work.

4. NECESSITY OF ESTIMATES
To knowabout theapproximatecostof the
building construction.
Tocalculate the tax of thebuilding
Tofix the rent of building
The know about the various items of works
involved in the building construction andarrange
the available materials of theconstruction.
Toarrange the laboursof theconstructionworks.
Take theapproval forthegovernment projects.
Tohaving the loan from thebank.

5. 1) DRAWINGS
If the drawings are not clear and without complete dimensions the
preparation of estimation become very difficult. So, it is very essential
before preparing an estimate.
2) SPECIFICATIONS
a) General Specifications:
This gives the nature, quality of work and materials in general terms to be
used in various parts of wok. It helps to form a general idea of building.
b) Detailed Specifications:
This gives the detailed description of the various items of work laying down
the Quantities and qualities of materials, their proportions, the method of
preparation workmanship and execution of work.
DATA REQUIRED TO PREPARE AN ESTIMATE

6. 3) RATES
For preparing the estimate the unit rates of each item of work are
required.
1. For arriving at the unit rates of each item.
2. The rates of various materials to be used in the construction.
3. The cost of transport materials.
4. The wages of labor, skilled or unskilled of masons, carpenters,
Amador, etc.,
LUMPSUM:
While preparing an estimate, it is not possible to work out in detail
in case of petty items. Items other than civil engineering such items
are called lump sum items or simply L.S.Items.
DATA REQUIRED TO PREPARE AN ESTIMATE
DATA REQUIRED TO PREPARE AN ESTIMATE

7. QUALITIES OF QUANTITY SURVEYOR/ESTIMATOR
Thequantitysurveyor must bewell versed with the
drawing of work.
He should be able toread thedrawing correctlyand
bill the quantitiesaccurately.
Heshould have the knowledgeof theconstruction
procedure
He should be able towrite thedescriptionof different
works.
He should able toprepare the scheduleof the project
Heshould beable tovalueall variations underthe
contract.

8. To Prepare an estimate
To prepare specifications
To carry out survey of buildings and land.
To carry out rate analysis
To finalise the final accounts.
To supervise engineering structure during execution.
To prepare work execution schedule
To work as arbitrator
To carry out valuations of the property
To advise the architect and the local authorities about
the estimated cost of the project and construction of the
structure.
DUTIES OF A QUANTITY SURVEYOR OR ESTIMATOR

9. The estimates may be divided in to the following categories:-
(1) Preliminary or Approximate estimate.
(2) Detailed estimate.
(3) Quantity estimate
(4) Revised estimate
(5) Supplementary estimate.
(6) Supplementary & Revised estimate
(7) Annual repair & maintenance estimate.
TYPES OF ESTIMATE

10. Preliminary Estimate is prepared by various ways for different
structures as mentioned below :
 Buildings
Per Unit Basis – Per student for schools and hostels, per class
room for schools, per bed for hospitals, per seat for cinema
and theatre halls, per tenement for residential buildings.
Plinth area basis
Cubic content basis
Appx. Quantity method
 Roads and Highways – Per km basis depending upon nature of
road, width and thickness of metalling.
 Irrigation Channels
Per km basis
Per hectare basis (Area of land commanded)
PRELIMINARY ESTIMATE

11.  Bridges and Culverts – Per running meter of span depending
upon type of structure, type and depth of foundation.
 Sewerage and Water Supply Project
Per head of population served
Per hectare basis (Area covered)
 Over Head water Tank – Per liter or per gallon of tank
depending upon type of structure and height of tank.
PRELIMINARY ESTIMATE (Ctd.)

12.  It is the accurate estimate prepared by working out quantities of
each items of work.
 It is prepared in two stages –
 Details of measurements and calculation of quantities.
 Abstract of estimated cost – 3% to 5% of estimated cost is added to
cover miscellaneous expenditure
 Detailed estimate is prepared work-wise.
 Detailed estimate consists of –
 Report
 General Specifications
 Detailed specifications
 Drawings
 Calculation and designs
 Analysis of rates
 Detailed estimate is prepared for technical sanction, for
arranging contract and for execution of project.
DETAILED ESTIMATE

13. QUANTITY ESTIMATE
This is a complete estimate or list of quantities for all items of
work required to complete the concerned project.
The quantity of each individual item of work is worked out from
respective dimensions on the drawing of the structure.
To find the cost of an item its quantity is multiplied by the rate
per unit for that item.
The purpose of the bill of quantities is to provide a complete list
of quantities necessary for the completion of any engineering
project and when priced gives the estimated cost of the project.

14.  Revised estimate is prepared when original sanctioned
estimate is likely to exceed more than 5%.
 When expenditure on work is likely to exceed amount of
administrative sanction by more than 10%
 When there are material deviation from original proposal even
though cost may be met from sanctioned cost.
 It is accompanied by comparative statement showing
variations in each item of works and reason for the same.
REVISED ESTIMATE

15.  It is the fresh detailed estimate of the additional works in
addition to the original estimate.
 It is required when further development is required during the
progress of work.
 Abstract should show the amount of original estimate and
total amount including supplementary amount.
SUPPLEMENTARY ESTIMATE

16.  When a work is partially abandoned and estimated cost of
remaining work is less than 95% of original sanctioned
estimate.
 When there are material deviations and changes in the design
 If at any time before or during the execution of work, it is
found that original estimate is excessive then divisional
officer may sanction a revised estimate of reduced amount.
SUPPLEMENTARY AND REVISED
ESTIMATE

17.  It is prepared to maintain structure or work in proper order
and safe condition
 For buildings like white washing, painting, minor repairs etc.
 For road works A.R. estimate provides for patch repairing,
repairs of bridges and culverts etc.
ANNUAL REPAIR OR MAINTENANCE
ESTIMATE (A.R/A.M ESTIMATE)

18. 1. Service unit method :
•The service unit indicates the most important, unit in a
structure. The entire structure is divided into number of
service units. For example, in a schoo1 building, the service
unit is a class room.
•The rate of service unit is decided from the information of
similar construction in the area. Then, approximate cost of a
structure = Number of service units in the structure x Cost of
service unit in a similar existing structure. The service units
for various structures are given in the table below:
METHODS OF PREPARING APPROXIMATE ESTIMATE

19. SERVICE UNIT METHOD

20. •Plinth area = Area of the building at the plinth level,
measured out to out of walls.
The estimates are prepared on the basis of plinth
areas of the various buildings proposed to be constructed.
The rates are being arrived at the dividing the total cost of
construction with its plinth area.
•The following documents are attached with the estimate.
(a)Line plan with brief specifications.
(b)Cost of various services added i.e. electric and water supply
etc.
(c)North line should be shown clearly on line plan.
PLINTH AREA METHOD

21. Floor Area Plinth Area

22. •Floor area = Plinth area - area of walls
•In the calculation of area of walls, the thickness of the wall
shall be inclusive of finishes and dado if the height of such
finish is more than 1 m from floor finish .
The following shall be included in the wall area
{i) Door and other openings in the wall.
(ii} Built in cupboard appearing within a height of 2.2 m
from floor.
(iii) Flues which are within the wall.
(iv) Intermediate columns.
FLOOR AREA METHOD

23. •The carpet area is the floor area less the area of the
following portions (as per IS : 3861)
(i) Verandah
(ii) Corridor, Passage .
(iii) Entrance hall and Porch
(iv) Stair case
(v) Bathroom and W.C.
(vi) Kitchen and pantry
(vii) Store, machine room for lift
(viii) Shaft for sanitary pipes, etc.
Estimated cost = Carpet area x Carpet area rate
CARPET AREA METHOD

24. •In this method the cost of water supply, drainage,
electrification, etc. ancillary works is estimated as some
percentage of the total construction cost of building.
Cost-Percentage Item of total cost
1. Water supply = 4%
2. drainage = 4%
3. Electrical installation = 5 to 8%.
PERCENTAGE METHOD

25. •In this method, the cost per m3 used as a base for finding
out approximate cost of the proposed building.
•Cubical content of the building = Plinth area x height
of building
•While calculating the height of building, the depth below
plinth is not considered. If the roof is sloping, average height
is taken. Normally, distance between floor level and slab top
level is taken as the height.
Approximate cost of proposed building= Total cubical
content of building x Cube rate
CUBICAL CONTENT METHOD

26. •This method is useful in case of buildings which have several
similar bays.
A bay is a space from centre to centre of two successive
columns. A typical interior bay is selected and its total cost is
worked out.
•Approximate cost of proposed building =Number of
bays *Cost of one bay .
Following points are to be noted :
(i) Necessary corrections should be made for end bays due
to end walls.
(ii) Sufficient allowance should be made to compensate for
the small things that are over-looked.
TYPICAL BAY METHOD

27. EMPIRICAL EQUATIONS OF CBRI
•The quantities of materials and labours required for a particular
residential building can be worked out with help of certain
empirical equations developed by CBRI (Central Building
Research Institute Roorkee).
•Following are such equations: A -=Plinth area of building in m2.
1. Cement in tonnes = 0.153 A + 0.57
2. Sand in cu m =0.47 A- 7
3. Aggregate (C.A.) in cu.m -=0.145 A + 1.5
4. Bricks in Nos. = 226 A + 6680
5. Steel in quintal = 0.213 A - 3.14
6. Mason in Nos. = 1.335 A + 28
7. Mazdoor in Nos. = 4.766 A - 32

28. APPROXIMATE QUANTITIES METHOD
•In this method, various quantities are worked out with the help
of many short cuts. For instance, the wall foundations are
measured in linear measurements i.e. in running metres.
•The approximate quantities of items such as excavation,
foundation PCC, brick masonry up to plinth, D.P.C. are
computed per running length and with the help of rates of
these items, a fairly accurate price per running metre is
obtained.. This price when multiplied by the total running
measurements gives the approximate cost of the building up to
plinth level.

29. COST COMPARISON METHOD
•This method is suitable for the estimate of prototype
structures. For example when prototype staff quarters or
railway stations etc, are required to be estimated
approximately then the estimate for such prototype works are
prepared by comparing the previous cost with the present
market rates, normally be increasing the past cost on a
percentage basis.

31. IMPORTANT TERMINOLOGY
 Provisional Sum
Prime Cost
Provisional Quantities
Spot Items
Day Work
Contingencies
Work Charged Establishment
Charges
Water Charges
Over Head Charges

32. •Provisional sum is the amount provided in the estimate and bill
of quantities for some specialised work to be carried out by a
specialist firm; whose details not known at the time of preparing
estimate.
•e.g. installation of lift installation of air conditioners shifting of
water lines, sewer lines electrical fittings, etc. For such items, a
reasonable amount is provided in the estimate and in the bill of
quantities, known as provisional sum.
PROVISIONAL SUM

33. •When quantities of various items are being worked out, it is not
always possible to define everything necessary for the completion
of the proposed building. Certain items such as, water supply
fittings Sanitary fittings door and window fittings, etc. are to be
decided by the architect in consultation with his client at some
future date.
•Hence, the details of such items are not worked out at the time of
inviting tenders, but for the execution of such items, a lumpsum
amount is put up in the bill of quantities. This amount is Some
known as Prime cost.
PRIME COST

34. • When the quantities of a particular item are not certain,
provisional quantities are provided separately for such items. For
this purpose, measurements of the item are taken usual but kept
separately in the bill of quantities and marked as “Provisional”
•For a building if the nature of soil is uncertain, and if it is
thought that extra depth of foundation, will be required then
normal quantities of earthwork, foundation concrete and brick
work will be calculated from the dimensions given in the drawing
and the additional quantities of earthwork, foundation concrete
and brickwork due to the probable extra depth are worked out
separately and these additional quantities are marked as
Provisional quantities.
PROVISIONAL QUANTITIES

35. • There are certain items for which it is not possible for the
estimator to fix an amount without seeing and studying them in
detail. Such items are known as “spot items”.
•The estimate of such items can be prepared only after inspection
and taking detailed measurements at site.
•Some of the spot items are as follows
demolishing existing structures.
Constructing openings in the existing wall
Clearing the site
Connecting an old building to a new building
SPOT ITEMS

36. • The term day work' is used to denote a procedure of costing or
valuing an item of work on the basis of the materials used, the
actual time taken by the labourers and the equipment employed.
•The day work is adopted for certain complicated items of work
which can not be measured as
1.Design in the plaster work
2 .Front architectural finish of a building
3 .Work under water Ornamental door, etc.
are valued and paid by day work.
DAY WORK

37. • For drinking purpose of the workers and for the work,
arrangement of water either by sinking tube well or municipality
becomes necessary.
• In order to meet up the expense an amount of 1 to 1.5% of the
total cost of materials and labour has been provided in the
analysis of rate.
WATER CHARGES

38. OVERHEAD CHARGES
Overhead charges include general office expenses, rents, taxes,
salaries of office staff, and other costs which are indirect expenses and not
productive expenses on the job.
The overhead charges may be under thee two heads :
• Establishment (office staff)
• Stationary, Printing
• Postage
• Travelling expenses
• Telephone
• Rent
• Taxes
• Electrical bills, etc.
a. General overheads :
b. Job overheads:
• Salary of engineers
• Supervisors Handling of materials

39. • It Indicates incidental expenses of miscellaneous character
which cannot be classified under any distinct item. (3% to 5%
of the estimated cost is provided to allow for contingencies)
CONTINGENCIES

40. WORK-CHARGED ESTABLISHMENT
•During the construction of a project considerable number of
skilled supervisors, work assistance, watch men etc., are employed
on temporary basis. The salaries of these persons are drawn from
the L.S. amount allotted towards the work charged establishment.
•Work charged establishment charge is charged directly to work a
Lump -Sum amount of 1.5 to 2% of the estimated cost is provided
towards the work charged establishment.

41. THANKING YOU