Approximate estimate

Unit No-2
Approximate Estimate .
Course outcome:-
Prepare approximate estimate of a civil engineering works.

UO 1 Explain the necessity of approximate estimate in the given
situation.
Approximate estimate or preliminary estimate:
• To give the rough idea of probable expenditure in short time without calculating
the actual quantities, from the cost of similar structure having similar specification,
construction & locality.
• This estimate is required for preliminary studies of various aspects of work or
project, to decide the financial position and policy for administrative sanction by
the competent authority. In case of commercial projects as irrigation projects,
residential, building project and similar project which earn revenue, the probable
income may be work out. To prepare the approximate estimate less skill and time is
required.
• The accuracy of the cost estimated by such approximate estimate depends upon
the judgment, skills and experience of estimator and upon the correctness of the
prices.

UO 1 Explain the necessity of approximate estimate in the given
situation.
Purpose of approximate estimate:-
• To give the rough idea of probable expenditure in short time without
calculating the actual quantities, from the cost of similar structure having
similar specification, construction & locality.
• In case of Government & public bodies, for sanctioning of the expenditure
required for the project in the form of Administrative approval.
• In case of commercial projects to study the cost-benefit ratio. If it is justified
the project is carried out.
• For BOT/PPP Systems approximate estimates plays important role for
decision making & for preparation of Feasibility Report of Project.
• For framing Tax Schedule & Insurance requirement.
• For buying & sailing and Rent Fixation.

UO 2 Describe the method used in determining the approximate estimate for
the given structure.
Methods of approximate estimate:-
1. Plinth area method.
2. Cubical content method.
3. Service unit method.
4. Typical bay method.
5. Approximate quantity method.
1. Plinth area method:-
• This estimate is prepared on the basis of plinth area of building. The rates are
obtained from a similar building having similar specification, heights and
construction in the locality. Plinth area estimate is calculated by finding the plinth
area of the building and multiply by the plinth area rate.
• Rate of construction on plinth area basis
= Cost of structure/ Plinth area of structure
• Cost of proposed building = Plinth area x Plinth area rate
• The plinth area should be calculated for the covered area by taking external
dimensions of the building at the floor level. Courtyard and other open area should
not be included in the plinth area.
• Such estimate are vary approximate and varies according to shapes, sizes, types of
construction and locality.

UO 2 Describe the method used in determining the approximate estimate for
the given structure.
Example:-
The cost of construction of Govt Polytechnic Nanded Building is 2 crores for a capacity
of 500 students and area of construction about 2000 sq.m Prepare approximate
estimate of a newly proposed of Gov Poly Building for 1200 students with the area
5000 sq.m
Given data:
Cost of existing structure: - 2 Crores
No of students:- 500 nos.
Plinth area:- 2000 Sq.m
No of students for new construction:- 1200 Nos.
Plinth area of new Construction: 5000 Sq.m.
Solution:-
Rate of construction per Sq m
= Cost of existing structure/ Plinth area of existing structure
= Rs. 200,00,000/2000m2
= Rs.10,000/- per Sq m.
Approximate cost of Proposed polytechnic
= Rate of construction X Plinth area of new Construction
= Rs.10,000 X 5000
= 500,00,000 (5Crores)

UO 2 Describe the method used in determining the approximate
estimate for the given structure.
2. Cubical content method:-
• It is an approximate estimate. It is prepared on the basis of cubical content
of the building .
• The cube rate is determined from the cost of similar building having similar
specification and construction in the locality.
• This is calculated by finding the cubical content of building (l x b x h) and
multiplying it by cube rate.
• It is more accurate as compared to plinth area estimate.
• The cubical content of building must not include foundation, plinth and
parapet above roof.
Example:-
A residential building of G+4 has been constructed in pune and having a plinth
area of 1200 sq.m. Height of building is 16.5 m above ground level. The cost of
construction of building is 6,00,00,000/-. Using method of cube rate estimate,
prepare an estimate of building of 12 m height and plinth area 2900 sq.m. It
has four floors.

Given data:-
Cost of construction of existing building:- 6,00,00,000/-
Plinth area:- 1200 sq.m
Height of building:- 16.5 m
Plinth area of new construction:- 2900 Sq.m
Height of building:- 12 m
Solution:-
Rate of construction on cube rate basis
= Cost of construction of existing building / Volume of building.
= 6,00,00,000 /( 1200 x 16.5)
= Rs. 3030.30
Approximate estimate of new building
= Rate/cum x Volume of new building.
= 3030.30 x ( 2900 x 12)
= Rs. 10,54,54,440/-

3. Service unit method:-
• Each building constructed to serve some purpose.
• For example hospital is designed to accommodate certain number of beds.
Each bed is then as service unit of a hospital.
• Whenever a building is constructed, the engineer keeps the record of the
place of construction, actual cost of construction, number of service units
etc. From this record, it is possible to work out the cost of construction per
service unit.
• While preparing approximate estimate by this method per students for
hostel, per students for school, per class room for school, per bed for
hospital, per seat for cinema halls, per bay for factories is considered.
• Cost of construction per service unit
= Total cost of construction / total no of service units
• Such estimate are vary approximate and varies according to shapes, sizes,
types of construction and locality.
• Example:-
• Prepare approximate estimate of a bridge having 4 spans of 50 m each
using following data. (i) Cost of existing bridge Rs.1.5 cr. (ii) Existing bridge
having 3.3 spans of 60 m each.

Given data:-
Cost of existing bridge :- Rs.1.5 cr.
Length of span :- 60 m each
No of span :- 3.3 Nos.
Length of span of new bridge:- 50 m
No of span of new bridge :- 4 Nos.
Solution:-
Length of existing bridge = No. of spans x length of each span
= 3.3 x 60
= 198 m.
Rate per meter length = Cost / Length
= 1,50,00,000 / 198
= 75757.58
Length of new bridge = No. of spans x length of each span
= 4 x 50
= 200 m
Approximate cost of new bridge = 200 x 75757.58
= Rs. 15151516

4. Typical bay method:-
This method is useful and is generally followed in case of buildings having
several bays.
The cost of the typical bay is worked out and is then multiplied by the number
of bays in that building.
The extra cost for the end walls and difference in framing, if there is any,
should be made, so as to arrive at the correct cost.
This method is used for preparing estimate of factory building.
Approximate Cost = Number of bay x Cost of bay
Example:-
Prepare approximate estimate of a factory building from following data:
office premises- RCC frame type.
Total area 150Sq.m built up.
Workshop- 4 bays of size 4 m x 8 m with load bearing walls and AC sheet roof.
Plinth area rates, RCC building- 18000/- sq.m
Load Bearing building- 6500/- sq.m

Given data:-
Built up area - 150 Sq.m
Plinth area rates For RCC - 18000/- Sq.m
Plinth area rates For Load bearing - 6500/- Sq.m
No of bays -04 Nos
Size of one bay - 4 m x 8 m
Solution:-
Approximate Estimate of a factory building:
1. Office premises:
Approximate cost = Total built up area x Rate per Sq.m
= 150 x 18000
= 27,00,000/-
2. Workshop with 4 Bays:
Cost of one bay = Size of one bay x Rate of each bay
= (4x8) x 6500
= 2,08,000/-
Approximate cost of bay = No of bays x Cost of one bay
= 4 x 2,08,000/-
= 8,32,000/-
Total approximate Cost = Cost of office premises + Cost of workshop
= 27,00,000 + 8,32,000
= 35,32,000/-

5. Approximate quantity method:
• In this method the structure is divided into:
a) Foundation Inclusive of Plinth
b) The Super Structure.
• The cost per running meter of foundation inclusive of plinth is worked out and is
multiplied by the total length of foundation to determine the total cost of
foundation inclusive of plinth.
• Similarly the cost per running meter of the superstructure is found out and is
multiplied by the total length of all the walls of superstructure to get the total cost
of superstructure.
• The total cost of the structure is then obtained by the addition of total cost of
foundation inclusive of plinth to the total cost of the superstructure.
• The running meter cost for foundation and superstructure should be calculated first
and then running meter rat should be multiplied by total length of walls.
• For this method plan of building must be available.

UO 3 Prepare the approximate estimate for given civil engineering
Works.
1. Approximate Estimate for Roads and Highway:-
Approximate estimate for roads and highways is prepared for per kilometer
basis depending on the nature of road, width and thickness of metal etc. for
roads and highways the factors to be considered area, land to be acquired,
quantity of earthwork, type of road etc.
1. The cost of land acquired: The cost is variable if the route is passing
through highly developed area, the cost of this item will be very high.
2. The cost of excavation, embankment and drainage: The cost of this item
depends on the topography of the country through which the highway
runs.
3. The cost of road surface or pavement: the cost of this item is fairly
constant for two different highways with same road surface. e.g. for 10 km
of a state highway approximate cost @ Rs. 500000 per 1 km works out as
Rs.50 lakhs.

2. Approximate estimate of railway project:-
• For estimate of a railway project main items or works are foundation, embankment
in cutting and banking, bridge, level and road crossing, fencing, boundary, km post,
gradient post, office building, platform, staff quarters, workshop, sanitary
arrangement etc.
• Railway estimate are prepared by knowing the cost per km of recently constructed
similar railway line i.e. same gauge, sleeper, ballast etc.
• While preparing approximate estimate, cost of land acquisition also be included.
3. Approximate estimate of bridges and culverts:-
• Approximate estimate of bridges are prepared on the basis of per running meter of
span or per running meter of linear water way.
• Approximate estimate of bridge depends upon road way, nature of bridge, depth
and type of foundation etc.
• Approximate cost of new bridge is work out by determining total number of spans
or total length of linear water way and multiplying it by rate of construction per
meter length of a recently constructed similar bridge with the similar
specifications.
• For culverts approximate cost may be determined per meter of span, per meter of
linear water way or per number of culvert of different span.
• Approximate cost of bridge and culvert can also be workout according to sub
structure and super structure respectively.

4. Approximate estimate of irrigation project:-
• There are different systems of irrigation. But in general the method of preparing approximate
estimates involved the following steps.
• Statements of objects – It should be ascertained whether the project is for single purpose i.e. to
serve only one purpose or multiple purpose project i.e. serve more purposes.(Like Irrigation,
Hydroelectric power, water supply etc.)
• Collection of data – To arrive at reasonable decision from the preliminary estimate reliable data
(like physical, Hydrologic, Geological, Agricultural etc.) to serve the objects are collected and
furnished to prepare the approximate estimate.
• Projections of planning - The future needs should be evaluated. The true economical demand in
future period is estimated.
• Project Formulation – Comprehensive list of all the possible alternative units should be prepared
and defined the boundary conditions which restrict the project. In the Catalogue all the possible
project units along with the alternative plans for each project unit is indicated.
• Project Evaluation–
• Preliminary estimate for each of the catalogued project units are prepared by comparison of cost
method.
• The approximate cost of the proposed units is found by modifying the known cost of similar units
constructed previously in accordance with one particular cost index figure.
• Approximate estimated cost of units of irrigational canals may be prepared per kilometre basis
depending on the capacity of canal or multiplying the commanded area in hectares’ of
canals by approximate average cost per hectare.
• From alternative units the most efficient unit whose benefit cost ratio is more than one, the unit
or units may be recommended for construction.
• An amount for contingency (normally 10%) is added to the cost of project.
• For overheads as percentage (usually 10%) cost of the approximate estimate is included in the
estimate.
• At last the cost for land acquisition (normally 12%) is added to frame the total approximate
estimated cost of a project.

5. Approximate estimate for water supply project:
• Basis of preparing approximate estimate of Water supply project may be
population to be served by project.
• In this case knowing cost of recently constructed similar water supply project, cost
per capita can be found out, and then approximate cost of new project can be
calculated.
• Otherwise water supply project is divided in to following units and approximate
cost of each unit is found out and then total approximate cost of project is
calculated.
Sr. No. Unit Service unit
1 Intake or head work Per MLD OR Per m3 capacity
2 Pumping machinery Per H.P. OR KW
3 Rising main Per running mater
4
Treatment unit like aerator, flash mixer,
clarifloculator, rapid sand filter,
disinfection.
Per MLD OR Per m3 capacity
5 Ground storage reservoir and ESR Per liter capacity
6 Distribution system Per running meter
7 Staff quarter Per Sq. m.
8 Land acquisition Per Acre

Solved Examples
1. Prepare approximate estimate of a town hall building having plinth area equal to
1500 m2. Plinth area rate Rs. 4,000 per m2.Water supply and sanitary installation- 5 %
of cost of building. Electric installation – 10% of cost of building. Other services-5% of
cost of building. Contingencies – 3% of. overall cost of building.Supervisioncharges-8
% of overall cost of building. (Summer 2016)
• Given:-
Plinth area =1500 m2
• Plinth area rate =4000persq.m
• Approximate estimate = Plinth area x Plinth area rate
• =1500x4000
• Cost of building = Rs 60,00,000 /- ………………A

2. Prepare approximate estimate of a public building having plinth area equal to 1800
sq.m.
i. Plinth area rate as Rs. 3,500 / sq. m.
ii. Special architectural treatment = 3% of cost of building.
iii. Water supply and sanitary installation = 5% of cost of building.
iv. Electric installation =14% of cost of building.
v. Other services = 5% of cost of building.
vi. Contingencies = 3% of overall cost of building.
vii. Supervision charges = 8% of overall cost of building. (Summer 2015)
• Solution:-
Cost of construction: P x Plinth area rate
=1800x3,500
=Rs.6,300,000
Special architectural treatment =3% of cost of building
=3/100(6,300,000)
=RS.1,89,000
Water supply and sanitary installation = 5% of cost of building
=5/100(6,300,000)
=Rs.3,15,000
Electric installation =14% of cost of building
=14/100(6,300,000)
=Rs.8,82,000

Other services =5% of cost of building
=5/100(6,300,000)
=Rs.3,15,000
Overall cost of building = 6,300,000 + 189,000 + 315,000 + 882,000+315,000
=Rs.80,01,000
Add Contingencies =3% of overall cost of building
= 3/100 (8,001,000)
=Rs.2,40,030
Add Supervision charges = 8% of overall cost of building
=8/100(8,001,000)
=Rs.6,40,080
Grand Total = 80,01,000 + 2,40,030 + 6,40,080
= Rs. 88,81,110

3. Prepare approximate estimate for public building from given data:
Plinth area = 2200 sqm
Plinth area rate = 3500/sqm
Electric installation charges = 8% of cost of building.
Water supply charges = 3% of cost of building
Contingencies = 2% of overall cost of building
Engineer supervision charges = 4% of overall cost of building.(winter 2017)
Solution:-
Approximate estimate for public building:
Cost of building=plinth area x rate
=220x3500
=Rs.77,00,000/-
cost of electric installation charges= 8% of cost of building
=8/100(7700000)
=Rs.6,16,000/-
iii. Cost of water supply = 3 % of cost of building
=3/100 x (7700000)
=Rs.231000/-Overall cost of building
= (7700000+616000+231000)
=Rs.85,47,000/-

iv. Cost of contingencies = 2% of overall cost of building
=2/100 x (8547000)
=Rs.1,70,940/-
v. Engineer supervision charges = 4% of overall cost of building
=4/100x(8547000)
=Rs.3,41,880/-
Total cost = (8547000 +170940 +341880)
=Rs.90,59,820/-
Hence approximate estimate of given public building is Rs 9059820/-

4. The cost of construction of school building is 2.50 crores for a capacity of 600
students and area of construction is 1600 m2. Prepare approximate estimate of a
newly proposed school building for 1500 students with the area of 5000 m2.Use
plinth area method. (Winter 2015)
Solution:-
Cost of plinth area of existing school building =2,50,00,000/1600
= 15625 Rs/m2
Then,
The approximate cost of newly proposed school building
=Total plinth area of proposed building X cost per Plinth area of similar existing
building
= 15625 X 50000
= 7.8125 crores

Approximate estimate

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