Introduction and Approximate Estimates
Introduction
and Approximate Estimates
By
Sudarshan
Sampatrao Bobade
Assistant
Professor
Department
of Civil Engineering
PCET’s
PCCOER, Ravet
Pune-
412101
Unit
I
Introduction
and Approximate Estimates [6
Lectures]
a) Introduction to estimates and related terms:
Definitions of estimation and valuation:
Estimation:
Ø A rough calculation of the value, number, quantity,
or extent of something.
Ø A judgment of the worth or character of someone or
something.
Valuation:
Ø An estimation of the worth of something, especially
one carried out by a professional valuer. "it is wise to obtain an
independent valuation"
Ø The monetary worth of something, especially as estimated
by a valuer.
Significance (application) of the Course:
This course covers the various aspects of estimating
of quantities of items of works involved in buildings, water supply and
sanitary works, road works and irrigation works. This also covers the rate
analysis, valuation of properties and preparation of reports for estimation of various
items. At the end of this course the student shall be able to estimate the
material quantities, prepare a bill of quantities, make specifications and
prepare tender documents. Student should also be able to prepare value
estimates.
Purpose of estimation:
Ø To have an Idea of overall construction cost
Ø Estimation for Public construction is needed to have
and administrative approval, technical sanction and funds
Ø For timely procurement of materials as per the
estimated quantities
Ø To make a construction programme and prepare
schedule
Ø To set the deadlines for various construction
activities
Ø Determine requirement of tools, equipment and plants
Ø To arrange the labour as per work
Ø For Inviting tenders and prepare bills
Ø To measure benefit cost ratio
Ø For an existing, estimate is required for Valuation
Type of estimates, data required for estimation as a
pre requisite.
APPROXIMATE ESTIMATE –
It is also called budget, preliminary estimate. This
type of estimate is prepared in the initial stage of a project. To give a clear
idea to the owner (client) about the amount of cost needed for the project and
to get the approval from necessary sanctioning bodies (eg: from banks to get
loan). Documents such as project drawing plans, details about the land
including electricity & water supply and a full clear report are necessary
to carry out the estimate. Commonly the approximate estimate is calculated with
relevant to the previous experience.eg: To calculate the estimate for a house,
a previously (& also recently) completed similar house will be considered.
Here the estimator already knows the rate for 1m2 area & with
that he/she calculates the cost estimate for the newly proposed area (of
similar house).
Approximate estimate = Rate of 1m2
(already known value) X proposed area (m2)
PLINTH AREA ESTIMATE –
Plinth area estimate can be achieved by multiplying
the values of plinth length, plinth width & plinth area rate. Here the
plinth area is referred as, external plinth area of the building at floor
level. Simply it can be also stated as the roof covered area of a building.
Plinth area rate is derived by dividing the total cost of a previously
constructed building by plinth area of the previously constructed building.
Plinth area estimate = Plinth area X plinth area
rate.
Plinth area = plinth length X plinth width
Plinth area rate = Total cost of a previously built
building / Total plinth area of that building.
There are some restrictions in calculating the
plinth area of a building and some area have to include or exclude when
calculating. Among that, areas which can include are,
Floor area with area of walls at floor level
excluding the offsets of the building, internal shafts of sanitary fittings
within 2m2, lifts, air conditioning ducts, area of porch at floor
level (cantilever part can’t be included), area of barsati – a room on the
terrace or roof top with veranda outside.
Areas
which can’t include are,
Area of lofts, open balconies / un enclosed
balconies, fascia, towers which project above terrace level, louvers &
vertical sun breakers.
Documents such as line plan with complete
specifications & costs for services such as water, electricity should be
attached with estimate.
Meaning of an item of work, and enlisting the items
of work for different Civil Engineering projects.
CUBIC CONTENT ESTIMATE –
This type of estimate done by multiplying the volume
of the building by the unit cubic rate achieved from the previously (also
recent) estimate. This type of estimate is a little bit more accurate than
above mentioned methods and mostly suitable for multi storied buildings. Here
the cost of corbelling (corbel – a piece of stone, wood, brick, or other
building material, projecting from the face of a wall and generally used to
support a cornice or arch), cornice and other works like that are neglected.
Cubic content estimate = Volume of the building X
unit cubic rate (known value)
Volume of the building = plinth area (length X breadth
of the proposed building) X height of the building (floor to roof top)
Unit cubic rate = total cost of the previously built
building / total volume of that building.
ANNUAL REPAIR ESTIMATE AND SPECIAL
REPAIR ESTIMATE –
These estimates are prepared in order to maintain
the constructed element in good condition.
Works that attached when consider repair works, white washing, painting,
plastering works, patching works & etc. Special repair estimate is prepared
in situations where the costs of materials increased when compare to annual
repair estimate cost.
REVISED ESTIMATE-
This estimate is prepared when the rate of
previously submitted estimate increases by 5% or more than that. But here the
reason for the preparation of estimate must have a strong & valid reason
like sudden increase in cost of materials. The reason and comparative statement
between 2 estimates should be annexed with the revised estimate.
SUPPLEMENTARY ESTIMATE –
This type of estimate is prepared when there is a
necessary situation of supplementary work, to progress out the original work.
The annexure of originally prepared estimate & supplementary estimated
amount of the originally prepared estimate when submitting for requesting
approve.
DETAILED ESTIMATE-
Detail estimate is prepared with the help of
complete set of contract documents. The preparation of detailed estimate can do
under 2 phases such as work out with quantities of different works and
calculate the cost of each work.
1) work out with quantities of different works – The
whole construction work procedure is divided into categories such as excavation
and earthwork, concrete work, formwork, reinforcement, masonry work, roof
covering and roof plumbing, carpentry, painting and decorating, plumbing,
electrical installation and etc.
The measurement takeoff procedure is done with the
help of drawings/plans and then they are entered in measurement. Measurement
sheet is a prescribed form which contains number of columns to enter the
respective measurements and descriptions about the works. Finally the
measurement columns are multiplied to get the necessary quantity.
2) Calculation of the cost of each work – The
already obtained quantities is used to obtain the cost of each work. Calculated
costs of each work item are summarized in order and that document is called as
abstract sheet.
A detailed estimate should have documents such as
report, specifications, drawings/plans, design charts and schedule of rates.
Factors such as, material quantity, transportation of materials, location of
site, labour charges, cost of equipment (commonly allowed: - 2% of the
estimated cost), overhead charges (commonly allowed: - 2% of the estimated
cost), contingencies & unforeseen (commonly allowed: - 4% of the estimated
cost) items are needed to consider well while preparing the detailed estimate.
Note: The rate used to estimate should check with
current standard schedule of rates & in case of quantity, it should check
with standard data book.
Units
of measurement:
What is Unit?
The unit of measurement for any construction
activities depends on the nature of work being done, shape and size. They are
determinant of quantities of work being done. Following are the main principles
for measuring units:
1.
Measurement is
based on the finished item of work with detailed description of it.
2.
Following
order should be maintained: Length, Breadth, Height/Thickness.
3.
Least
dimensions should be:
a)
0.01m in
length
b)
0.01 m2 Sqft
in area
c)
0.01 m3 in
volume
d)
0.001 tons in
weight
Mode
of measurement of building items/ works:
1. Earthwork: It is measured in CUM or m3.
This includes all types of excavation. Vegetation removal and other extra work
are measured separately.
2. Backfilling: It is measured in CUM or m3.
This includes all types of filling work (generally the excavated material).
Vegetation it is measured removal and other extra work is measured separately.
3. Brickwork: It depends on how the bricks are laid.
4-Inch Brick work: It is measured in SQM or m2.
8-Inch Brick work: It is measured in CUM or m3.
* There should be no deductions for small openings
like pipe holes for scaffolding and openings less than 0.1 Sqm.
4. Stonework: Stonework is measured in CUM or m3.
* There should be no deductions for small openings
like pipe holes for scaffolding and openings less than 0.1 Sqm.
5. Concrete work: Reinforced Cement Concrete: It is
measured in CUM or m3.
Plain Cement Concrete: It is measured in CUM or m3.
Plum Concrete: It is measured in CUM or m3.
Chip Packing: It is measured in RMT or m.
* There should be no deductions for volume of pipes
or conduits smaller than 0.01 Sqm, volume of reinforcement bars and openings
less than 0.1 Sqm.
6. Tile
Flooring: It is measured in SQM or m2. It involves floor or wall tiling and any
other types of tiling work.
7. Weathering
Course: It is measured in SQM or m2.
8. Brick Bat
Coba: It is measured in CUM or m3.
9. Plastering:
It is measured in SQM or m2. Plaster work which is less than 30 cm
in width will be measured in RMT. Openings smaller than 0.5 Sqm should not be
deducted.
10. Painting: It
is measured in SQM or m2. Openings smaller than 0.5 Sqm should not be deducted.
It involves white washing, colouring, varnishing, Distempering.
11. Drip, string
course and water coping: It is measured in RMT or m.
12. Glazing: It
is measured in SQM or m2. Polishing and Rounding is measured in RMT.
13. Formwork: It
is measured in SQM or m2. Openings smaller than 0.4 m2
should not be deducted.
14. Centering
& Shuttering: It is measured in SQM or m2. Openings smaller than
0.4 m2 should not be deducted.
15. Scaffolding:
It is measured in SQM or m2 (if Height more than cum). Openings smaller than 0.4
m2 should not be deducted.
16. Door/ Window
Framing: It is measured in Numbers.
17. Hume Pipe
Installation: It is measured in RMT or m. And Rate will change with Diameter This
involves installation and testing.
18. Waterproofing
work: It is measured in SQM or m2.
19. Hacking/
Roughening: It is measured in SQM or m2.
20. Fixing GI
Mesh: It is measured in RMT or m.
21. Damp Proof
Course: It is measured in SQM or m2.
22. Dismantling:
It is measured in CUM or m3 & Sqm. m2 Both Depend upon Item.
23. Steel Work:
Steel bars in RCC work: It is measured in Quintal.
Bending/ Binding of steel: It is measured in
Quintal.
Rivets and Bolts: It is measured in Quintal.
Iron Railings/ Grills / Insert Plate : It is
measured in Quintal.
24. Pointing: It
is measured in SQM or m2. Pointing work which is less than 30 cm in width will
be measured in RMT. Openings smaller than 0.5 Sqm should not be deducted.
25. Piping: It is
measured in RMT or m.
Introduction
to components of estimates:
Face
Sheet
Sr. No. |
Particulars |
Amount |
01 |
Estimated cost |
Rs……. |
02 |
Water supply and sanitary charges @... % |
Rs……. |
03 |
Electrification charges @...% |
Rs……. |
04 |
Contingencies @... (3 to 5 %) |
Rs……. |
05 |
Work charge establishment @ (1 to 2 %) |
Rs……. |
|
Total Amount |
|
|
In words |
|
Abstract
sheet (BOQ):
Sr. No. |
Quantity |
Description or Particulars of Items |
Unit |
Rate |
Unit of Rate |
Amount |
||
|
|
|
|
Rs |
P |
|
Rs |
P |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
||
Measurement
Sheet:
Item No. |
Description
or Particulars of Items |
Number |
Length |
Breadth |
Height or
Depth |
Quantity |
Total
Quantity |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
Rate Analysis:
Rate Analysis can be defined as the analytical study
(qualitative and quantitative) that leads to the definition of a new unit rate
referring to a given job or work type, by identifying its basic elements.
Lead statement:
The distance between the source of availability of
material and construction site is known as "Lead” and is expressed in Km.
The cost of conveyance of material depends on lead. This statement is required
when a material is transported from a distant place, more than 8kms (5 miles).
The lead statement will give the total cost of
materials per unit item including first cost, conveyance loading-unloading,
stacking charges etc.
A
typical lead statement is provided as follows:
Sr. No. |
Material |
Unit |
Cost at Source (Per Unit) |
Lead in Km |
Conveyance Charges (per km/per
unit) |
Total Conveyance Charges
(per/unit) |
Total Cost (In Rs./Per unit) |
1 |
Rough stone |
Cum |
250.00 |
25 |
5 |
125 |
375 |
2 |
|
|
|
|
|
|
|
Provisional sum & Prime
cost items:
Prime
Cost
A prime cost is defined as ‘an item that has not
been selected, or whose value is not known, at the time a domestic building
contract is entered into and for the cost of supply and delivery of which the
builder must make a reasonable allowance in the contract’
What this essentially means is that these are items
that may not be selected yet – usually fixtures and fittings such as handles,
stovetops and tapware – as it’s too early in the process. In order to ensure a
consistent cost, the builder will make allowances for these items without
knowing the specific cost. This allowance will include any mark-up or profit
from the builder, as well as sourcing and installation costs.
Provisional
Sums
A provisional sum is defined as ‘an estimate of the
cost of carrying out particular work (including the cost of supplying any
materials needed for the work) under a domestic building contract for which a
builder, after making all reasonable enquiries, cannot give a definite amount
at the time the contract is entered into.’
This translates to works that the builder cannot
accurately price at the time of contract signing, like landscaping. It still
includes both the provision of materials and the labour costs.
Most simply, prime cost applies to items themselves,
provisional sums refers to complete works.
Contingencies:
The term `contingency’ represents any incidental or
miscellaneous character that cannot be classified under any distinct item
sub-head, yet pertain to the work as a whole. Contingencies in civil
engineering are important while preparing estimate of any construction project.
While planning any construction project, finalizing
a budget is one of the major steps in planning a successful project. Designing
and planning to project considering where to spend money and budgeting for all
the work takes both attention to detail and the complete scope of the project. However,
all estimate is correct and accurate there is some unforeseen issues or items
that come up where additional work will be needed. This is where a contingency
budget becomes critical. Contingencies in estimation and costing are an amount
added in the total estimate to balance incidental and miscellaneous expenses.
What
is the Amount of Contingencies Added?
To meet such unforeseen expense in construction
contingency estimates an additional amount of 3 to 5% of the estimated cost of
the work is provided in the total estimates. Miscellaneous incidental expenses
that cannot be classified under any subhead item, are met the amount provided
under contingencies. For estimating contingency is considered as 3 to 5 % of
the total estimated cost of the project.
Examples of Contingencies in Construction
There is an item of work cement plastering in a 1:3
mix ratio with a neat cement finish, but during execution, it is desired to
provide nosing at the end of steps. As there is no allocation of funds for this
small work, the cost of sub work may be met up from the contingency fund.
In case when expenditure is required for any
intermediate design change or due to an increased volume of work, and who
cannot be covered from the contingency fund, supplementary or revised estimate
submitted for its sanction before taking up the work.
If there is any saving against the amount provided
under contingencies amount may be utilized with the sanction of the competent
authority, to meet expenses of extra items of work.
The provision for contingencies may not be diverted
to ray new work or repair which is not provided in the estimate and of which
cost exceeds Rs. 2000 without the sanction of superintending engineer.
List of Contingency
Items in Construction
The Following is list of contingency Items in construction,
Extra work
which is added after starting of work
Any correction
after work started
Item whose
cost cannot be calculated in advance
Any mistake
during constriction
Types of Contingency in
Construction
Following are construction contingency examples and types used in
construction.
1. Contractor
Contingency
A contractor contingency is a fund into the contractor’s anticipated
price for the project to account for various risk factors that cannot otherwise
be accounted for in a schedule of values. This money is set aside to account
for any errors that occur on behalf of the contractor. Accordingly, contractors
consider these funds spent money.
Adding this extra fund to the
estimated cost of the project is the contractor accepting the fact that
unpredictable costs are all part of the construction biz. Construction
contingency is important before executing any project.
2. Owner Contingency
An owner’s reserve is an
amount set aside for additions or modifications of the scope of the work. Owner
contingency main utilized in guaranteed maximum price (GMP) contracts. Changes
and mistakes are not always the contractor’s fault. Any changes that are not
included in estimate or bid will have to be paid by the owner funded
contingency. Incomplete plans or owner directed changes are the leading causes
of dipping into an owner contingency fund.
Work charge
establishment:
The work changed establishment will include the temporary establishment
as are employed for the execution or the immediate technical supervision or
departmental stores in connection with the specific work.
Work charged staff may be technical person or an under staff of technical
person to assist him at work site, guard, etc. But work charged staff does not
include non-industrial employees such as the typist, draftsman, clerk, etc.
Every payment made to a member of the work charged establishment whether
on account of his wages or actual travelling expenses is charged to the work
estimate on which they are employed. For such work charged establishment an
amount of 1.5% to 2% (according to P.W.D.) of the estimated cost of the works
is provided in the estimate.
Generally, the work charged persons are employed on monthly basis or
temporary basis according to the progress of work. Their services lasts for the
sanctioned period but may be continued on fresh sanction. Their services are
terminable by one month’s notice for one year continuous service. But for less
than one year service, 14 days’ notice is required to terminate their services.
Centage charges:
Centage Charges means in connection with a work
which the Government execute on behalf of another Government, a local body or a
private party.
Introduction
to D. S. R.
The Schedule of Rates (Volume – I) is divided into
two sections, Section -I for works, Section -II for materials & Labour and
each section into sub-sections. In all cases of contracts in respect of
Building Works, this entire volume of Schedule will be operative. Though this
entire volume of Schedule is divided for convenience into sections and
sub-sections it is to be taken as a whole. An item under one section will apply
equally to work falling under the category of another section unless a similar
item appears in the later section. The same principle applies to items under
different sub-sections.
The ‘Engineer-in-Charge’ shall mean the Executive
Engineer of the Division concerned. The Sub Divisional Officer concerned is
authorized to carry out on behalf of the ‘Engineer-in-Charge’ general supervision,
day to day instructions with approval of materials and workmanship. In case of
dispute, the decision of the ‘Engineer-in-Charge’ shall be final and binding.
Except when specifically mentioned in the
description of the item itself, the rate for any item of work will apply
equally to all floors, in any position and up to any height. In respect of
concrete work etc. where the rate is on the basis of volume, the item shall
apply to all cases irrespective of the thickness unless a specific item appear
in the Schedule for the particular type of work. The work up to a particular
floor level means all work up to the roof of that floor. All works in basement
shall be treated as work in first floor for payment.
Renewal works include dismantling and taking out
of old works with mending good damages after renewal and removal of waste
materials. The rate for any item of original nature not provided in this Schedule
may be deduced from the rate of similar item of renewal work by multiplying by
a factor 100/105 and conversely the rate of any item of renewal nature not
provided in this Schedule may be deduced from the rate of similar item of
original nature by multiplying by a factor 105/100.
White washing, painting etc. include preparation
of surface (including plugging old nail holes etc.) prior to the treatment and
removal of all marks or stains from walls, floor, glass, panes, chowkats etc. For
repair works, this also includes shifting and/or covering furniture etc.
All works shall be carried out with due regard to
the convenience of the occupants, if any, and the arrangement and programme of
work must be adjusted accordingly. In case of works within Jails, Hospitals
etc. the Rules & Regulations of Authorities concerned must be strictly
obeyed. The rates given in the Schedule are deemed to be inclusive of all such
factors and contingencies.
All materials, tools and plants are to be arranged
for the work. All labours (Skilled & Unskilled) including their housing,
sanitation, procurement of food stuff, medical aids etc. are to be arranged by the
contractor. Cost of transport of labour, materials and all other relevant items
shall have to be borne by the contractor.
Arrangement of water for preparation of concrete
& mortar as well as for soaking of bricks and other materials are to be
made by the contractor. Construction of platforms and vats including cost
thereof are to be borne by the contractor.
If not specifically indicated in the items
themselves, the rates appearing in this schedule are inclusive of cost of all
supply, carriage, handling, fitting, fixing, toll charges, ferry charges etc.
and all other incidental works involved in any floor, at any level including
all necessary jointing materials, scaffolding to any height, hire charges of
tools and plants, and all ancillary materials but exclusive of GST.
To arrive at complete rate of different items in
this Schedule, 1% Sundries, 1% water charges, 5% overhead and 10% contractor’s
profit have been considered along with the aforesaid material cost, labour cost
and other cost etc.
Unless specifically mentioned otherwise in the
description of the item itself, no extra charges will be paid for scaffolding (including
stage scaffolding), centering, shuttering, curing etc. and the rates are deemed
to be inclusive of the same for the satisfactory completion of the work.
All materials brought to site must have approval
of Engineer-in-Charge. Rejected materials must be removed by the contractor
from the site within 24 (twenty-four) hours of the issue of orders to that effect.
In case of non-compliance with such orders, the ‘Engineer-in-Charge’ shall have
the authority for removal of those rejected materials at the cost and expenses
of contractor and the contractor shall not be entitled to any loss or damage on
that account.
Departmental materials (i.e. materials are
supposed to be issued by the department) shall be issued to the contractor to
the extent of requirements as assessed and in small installments as decided by
the Engineer-in-Charge. Issue of departmental materials may be of two
categories :
(A) Materials for which value are to be recovered
from the contractor.
(B) Materials which are issued directly to work (in
respect of items the rates of which do not include the cost of these
materials).
For materials under Category (A) the value of
materials issued to the contractor on usual hand receipt shall be recovered
from the bill of contractor in one installment or in successive installments as
may be decided by the Engineer-in-Charge.
For materials under Category (B) the contractor will
act as custodian of the department, when he shall take charge of the materials
against appropriate receipts signed by him. The contractor shall remain responsible
for the proper storage and safe custody of such materials. The rates of
relevant items of work shall be deemed to be inclusive of reasonable
consideration for such duties and responsibilities as the custodian.
All materials, whatever is the category thereof,
shall be properly stored by the contractor in suitable godowns within the site
of work. Under no circumstances, whatsoever shall any materials is removed from
the site of work without prior written permission from the Engineer-in-Charge.
The contractor shall be responsible for any damage or loss of such materials
unless he can satisfy the Engineer-in Charge that the reasons for such damage
or loss are due to circumstances beyond his control. The contractor shall also
have to satisfy the Engineer-in-Charge regarding the proper utilization of such
materials.
The value of any materials, which cannot be
satisfactorily accounted for, shall be recovered from the contractor’s bill or
other dues as specified in P. W. Department’s Order No. 2809(3)-A Dated 27.04.1971
as mentioned in West Bengal Form No. 2911.
Any materials under Category (A) which may be
surplus in few quantities on completion of the work may at the sole discretion
of the Superintending Engineer be taken back provided the same are found of non-perishable
nature and has not been damaged in any way. Surplus materials under Category
(B) shall be returned to the Engineer-in-Charge in good condition.
Subject to the aforesaid condition, the following
materials under Category (A) shall be issued to the contractor at issue rates
reflected against each. The materials shall be issued from the departmental godown
or godowns and for this purpose a stack-yard shall also be deemed as godown as
may be specified in the contract stipulations for any particular work. The
contractor will have to carry the materials at his own cost and his quoted rate
will be deemed to be inclusive of all such costs including costs for loading,
unloading and stacking.
i) Cement: Issue Rate and Basic Price of Cement are
shown in Table – 1-1 of Annexure – I. If cement is supplied by the Department,
the cost of cement will be recovered on Issue Rate, when in case of supply of
the same by the contractor, then rates of those cement related items are to be
deduced as per Format – A of Annexure - I. Except M35 & M40 Grade of design
mix concrete, rates of all other cement related items have been derived
considering PSC/PPC Cement. For M35 & M40 Grade of design mix concrete, OPC
(Grade – 43/53) cement has been considered in deriving the item-rates.
ii) Reinforcing Steel: Issue Rate and Basic Price of
Reinforcing Steel are shown in Table – 1-1 of Annexure – I. If Steel is
supplied by the Department, the cost of Steel will be recovered on Issue Rate,
when in case of supply of the same by the contractor, and then rates of those Steel
related items are to be deduced as per Format – B of Annexure - I. Cut pieces
of reinforcing steel materials left surplus on completion of work shall not be
taken back if the same be considered as unsuitable for utilization in other
works. Item-rates of structural steel and GCI Sheet have been derived
considering said materials to be supplied by the contractor.
iii) Empty Bitumen Drum: - Prevailing Schedule of
Rates (Volume – III) of PWD is to be followed. If in the interest of the work,
materials other than those mentioned above are to be issued under Category (A),
the issue-rate of such materials shall be based on the-then market rate or the
stock issue-rate whichever is higher. Such issue-rate shall be decided by the
Engineer-in-Charge and his decision shall be binding.
Materials obtained by dismantling Government
structures or parts thereof shall remain the property of Government. The
contractor shall sort out and stack the serviceable materials within the
premises and also dispose of the unserviceable rubbish etc. as per instruction
of the Engineer-in-Charge or his representative.
The contractor shall remain the custodian of such
dismantled materials till the charge of the same is taken over by the
Engineer-in-Charge or his representative.
The site must be cleared by the contractor from
time to time by removing rubbish, debris etc. as accumulated during the work
and on completion the whole site must be left in a clean and tidy condition to
the satisfaction of Engineer-in-Charge or his representative.
Number of full bricks salvaged by dismantling all
types of masonry part of the structure must correspond to at least 20% of the
volume dismantled.
Carriage of materials (unless specifically
considered in the Rate Analysis) is the sole responsibility of the contractor
for which no extra payment should be made (unless in exigency a few of those
seem to be justified by the Engineer-in-Charge, when the same are to be
approved by the concerned Superintending Engineer).
Approximate
Estimates:
An approximate estimate is an approximate or rough estimate prepared to
obtain an approximate cost in a short time. For certain purposes the use of
such methods is justified.
Meaning:
The approximate estimation is done in order to find out an approximate
cost in very short time before starting the project. The estimation is made
before selecting the final specification and design of the project. The method
is also known as Preliminary or Rough Estimation.
Purpose:
Ø To evaluate the cost of project in very short time.
Ø To evaluate difference between several options
Ø To check the final cost of the project that is
calculated by detailed estimation
Methods of approximate
estimation
1.
Square meter or Plinth Area Method:
This rough estimation is done by selecting the price
of 1 square meter area of building. It is mainly adopted for calculating the
cost of the following buildings:
a)
Office
Buildings
b)
Residential
Buildings
c)
School
buildings
d)
Apartment/
Flat Buildings
e)
Hospitals
The method is considered as the best method for calculating the cost of
the new buildings.
In case of multi - storeyed building, the following assumptions are to be
considered for estimation.
a)
For one square
meter area, the cost of all the floors with basement and the roof are in equal
costs
b)
The cost of
the basement is 60% of the floor.
c)
The cost of
the roofs is 40% of the floors.
2.
Cubic Rate or Cubic Meter or Cubic
Content Method:
For multi storeyed buildings, the following
assumptions are considered.
a)
For one meter
cube area the costs of all floors are equal in costs.
b)
The cost of
basement is 60% of the cost of different floors.
The volume of the floor is determined as:
Volume of the floor = Area X Height of One Floor
The Height of the floor is found out by the following guidelines:
1. Ground Floor: The height of the ground floor is
calculated from the top of the footing to the middle of the parapet
2. First Floor: The height of the first floor is
calculated from ground rooftop to the middle of the parapet.
3. Other Floors: The height of other floors are
calculated from floor to floor
Besides these methods, there are some other rough estimation methods such
as
1. Cost Comparison Method
2. Unit Rate Method
3. Approximate quantities with the bill method
4. Bay Method
Other Civil Engineering Projects
Method of preparation
approximate estimate for road projects
To prepare an approximate estimate Reconnaissance survey a narrow strip
of all the possible routes between selected termini is conducted to determine
the best possible routes and the approximate cost of the projected line.
The following information are collected from reconnaissance survey –
a. Extent of waterway for nallah and river crossings.
b. High flood level (H.F.L.) to determine the height of the road
embankment.
c. Number and length of more important bridges.
d. Total length of the alignment.
e. Probable amount of earthwork.
f. Geological characteristics of the areas to determine foundations of
bridges and stability of embankment.
g. Value of land.
In order to arrive at a fairly close estimate preliminary survey along a
route or routes selected as a result of reconnaissance survey is conducted to
determine the various distances, heights and angles.
From the above survey reports, maps and data preliminary estimates are
prepared per km basis by adding the following heads.
Ø Earth work estimate which includes provision of
borrowed and hauling earth. Approximate estimate may be prepared with the help
of contour map.
Ø Cost of road structures includes cost of bridges and
culverts. The spans of the structures are determined and an approximate
estimate is found by multiplying the span by cost per meter span of the
respective structures of items numbers.
Ø Cost of sub-base, consisting of soling and edging
according to the nature of the soil is selected and worked out for road width
per km.
Ø Cost of base course including premix carpet is
estimated from the cost per km basis.
Ø Cost of boundary pillars Rs.100 L.S. per km.
Ø Contingency 15 % and W.C. 5 % are added to the total
cost from heads (a) to (e).
Irrigation/ water supply:
Approximation estimate of irrigation project is prepared for storage
reservoir, canals and dams. Approximate estimate is prepared on the basis of
per million cubic meters of storage capacity or per square meter of catchment
area for storage reservoir and dams.
For irrigation channels per km basis, depending on the capacity of the
channel or per hector basis.
i.
Approximate
cost of 5 km long irrigation channel of 4 cum capacity @ 10 lakh is 50 lakhs.
ii.
Approximate
cost of 1000 hectors of command area @ 7000 is 70 lakhs.
Sanitary and Water Supply Works:
For sanitary and water supply works 8% of the estimated cost of works are
generally provided.
Sanitary engineering:
i.
On the basis
of per head of population served
ii.
On the basis
of area covered
Example:
Ø Approximate cost of sewage project for a population
of 100000 @ Rs. 750/- per head work out to be Rs. 750 lakhs
Ø Approximate cost of water supply project for a
population of 50000 people @ 500 per head works out to Rs. 2.5 Cr
Electrical works:
For electrification 8% of the estimated cost of work is generally
provided.
Electrical wiring shall
be measured in points such light point, fan point, plug point.
Classification: Point wiring shall be classified according to the length
of wire as follows:
Ø Short Points: Up to 3 m in length
Ø Medium: 3 to 9 m in length
Ø Long: 6 to 10 m in length
Ø Special Points: more than 10 m in length
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