CH.
APPROXIMATE ESTIMATION
Approximate estimation ( fast estimation ) :
The approximate estimation is prepared before laying the final
designs & specification and general specification of the project .
The purpose of the approximate estimation is to:
• Determine the cost of the structure quickly .
• Make an comparison between several alternatives .
• Checking the final cost of the structure which determined by
detailed estimation .
Methods of approximate estimation:
1- Floor – Area method . ( Price of one square meter of
the building ) .
2- Cubic method , ( volumetric method )
Floor – Area method . ( Price of one square meter of the building )
Use to determine the cost of the following building :
( Offices , Schools , Houses , Apartments , Hospitals …..etc. ) .
Is the best method for determining the cost of a new building , depend
on the results got from some old buildings which previously executed .
For multi-story buildings there are two assumptions :
• The cost of building all floors within basement and roof are equals for
one meter square of the built area.
• The cost of building the basement is taken ( 60% ) and roof ( 40% ) of
the cost of other floors .
Cubic method , (volumetric method )
• This method is more accurate than the floor-area method.
• For multi-story buildings apply the following assumptions:
• All floors are in equal costs for one cubic meter.
• The cost of the basement is (60%) of the cost of other floors.
• The volume of the floor is calculated as:
• The height of the floors is determined as follows:
• Ground floor : From the top of the footing to the mid height of the
parapet.
• Top floor : From the top of the ground roof to the mid height of the
parapet.
• Middle floors : From floor to floor.
Middle floor Top floor Ground floor
Example:
Building of dimensions ( 20m * 35m ) , have been executed and
composed of ( basement , ground floor , first floor , second floor , &
roof ) .
The total cost of the building was (1,100,000,000 ID).
Determine the rate of one meter square of the building depending
on the following assumptions:
•The (three floors, basement & roof) have equal cost per one meter
square.
• The cost of the basement is 60% of the cost of the other floors &
the cost of the roof is 40% of the cost of the other floors.
Solution:
First assumption:
basement area =700 m2
ground floor area =700 m2
1st floor area =700 m2
2nd floor area =700 m2
roof area =700 m2
Total =3500 m2
∴rate of one meter square of the
building=11000000003500=315000 ID
Second method :
For the second assumption (variable prices for each story):
Assume the rate of one square meter of constructing a building = X
Amount of building absement= 0.60X*700 ID =420X
Amount of building ground floor =X*700 ID
Amount of building first floor =X*700 ID
Amount of building second floor =X*700 ID
Amount of building roof slab =0.20X*700 ID=140X
Totl amount = 2660X =1100000000
110000000
X= =413500 ID
2660
Rate of basement =0.60*413500 =248100ID
Rate of roof =0.20*413500 = 82700ID
Example -2 :
Building of dimensions ( 40m * 60m ) , have been executed and
composed of ( basement , G. floor , 1st floor , 2nd floor ) . The
height of floors is as follows:
H. for basement = 2.80m.
H. for other floors = 3.0m.
Total cost of the building is (4,000,000,000 ID).
Determine the cost of the cubic meter, using the following
assumptions:
A. Cost of all floors is equal.
B. Cost of basement equal 60% of the cost of other floors.
Solution:
A/ 1st assumption:
volume of the basement =40×60×2.8 =6720m3
volume ofthe ground floor =40×60×3.0 =7200m3
volume ofthe 1st floor =40×60×3.0 =7200m3
volume ofthe 2nd floor =40×60×3.0 =7200m3
Total volume =28320m3
4,000,000,000
∴ 𝑟𝑎𝑡𝑒 𝑜𝑓 𝑜𝑛𝑒 𝑐𝑢𝑏𝑖𝑐 𝑚𝑒𝑡𝑒𝑟 = = 141000 𝐼𝐷/𝑚³
28320
B/ 2nd assumption:
volume of the basement =0.6×40×60×2.8 =4032m³
volume ofthe ground floor = 40×60×3.0 =7200m³
volume of the 1st floor = 40×60×3.0 =7200m³
volume ofthe 2nd floor = 40×60×3.0 =7200m³
Total volume =25632m³
∴Rate of one cubic meter=4,000,000,000/ 25632=
156000ID/m³
1. Approximate quantities :
Calculating of the approximate quantities of all general items of
the work , like ( foundations , walls, roofs , doors , D.P.C. , tiles ,
ceramics , sanitary services , electrical services ……etc. ), then
.multiply by the approximate rate of each item to get the
approximate cost of the building .
1. Modifications on the previous rates for approximate estimation:
Before calculating the approximate estimation, the previous rates
should be modified in order to be close to the existing rates therefore
the following notes should be taken into consideration:
1. The specifications and properties of the previous and existing project .
2. The date of execution of the two projects.
3. The position(location) of the two projects.
4. The general and special stipulations( ) الشروط العامة والخاصة.
5. The composition of the building (frame or bearing wall).
6. Shape of the buildings and their heights.
