Important formulae

1. Description Unit
Earthwork, Stone/Brick Work, Wood Work/Sunshadem3
Surface/Shallow Excavation m2
Pointing, Soling, DPC, Plastering m2
Steel/Iron Work kg/Quintel
Dressing of stone/Half Brick wall/partition wall m2
Painting Work/Distemper/Colour Washing/Jali Workm2
Degree ofAccuracy:WoodWork: 2mm,Weight – 1 kg, length
– 1 cm,Area – 0.01 m2
, Volume – 0.01 m3
 Purpose of Valuation
(a) Taxation– (10–14%)
(b) Rent fixation – (6 –10% of total value)
Outgoing: (a) Repairness – (10 – 15)% of total Income
(b) Management and collection Charge – (5 – 10)% of total
Income.
Scrap Value: It is about 10% of total value. It is the value of
Dismental Material.
Salvage Value: It is value at the end of Utility period without
being this dismental.
Sinking Fund:Annual Installment (I) = C
n
S.i.
I .S
(1 i) 1

 
(a) Straight line Method: Assume depreciation by same
amount D=
C S
n

(b) Constant percentage Method: Also called Balancing
Decline Method. It assume depreciation by same
percentage. D =
1/ n
S
1
C
 
 
 
General Overhead Cost Job Overhead Cost
Telephone Bill Salary Delay
Travelling charges Establishment of a New Office
Printing, Post office Compensation
Description Quantity
Work in foundation with Mud Mortar 1.5 m3
Work in foundation with Lime/Cement Mortar 1.25 m2
Work in Superstructure with Lime/Cement Mortar1 m3
Work in Superstructure mud Mortar 1.25 m3
Distemper (1 coat) 35 m2
White Washing/Colour Washing (3 Coat) 70 m2
White Washing/Colour Washing (1 Coat) 200 m2
RCC Work 3m3
Half Brick wall/Partition Wall 5 m2
Lime concrete in Roof 6 m3
Lime Concrete in foundation/Floring 8.5 m3
12 mm Plastering with cement/Lime Mortar 8 m2
Degree of Accuracy (descreasing order)
Detailed > Cube rate > Plinth area > Rough estimate
Area
Plinth area Floor area
Circulation area Carpet area
Vertical circulation area
Horizontal circulation area
(Staircase, Lift) (Varandaha, Passes)
4-5% of P.A. 10-15% of P.A.
 F.A. = Plinth area – area occupiedby walls/Intermediate sup-
ports
 Courtyard, play ground, unclosed Balcony, cantilever porch
is not included in plinth area.
 CarpetArea:Useable area/Living area
 C.A. =Totalfloorarea – (circulation area + Non-useablearea)
 C.A. in residential area (50 – 65)% and in commercial area
(60 – 75)%.
Work % of Estimate
Departmental charges (centage charge) (10 – 15)
Contractor charge 10
Labour Charge 25
Electrification 8
Electric fan 4
Saniatory and Water Supply Charge 8
Contigences Charges (3 – 5)
Work Charge Establishment (1.5 – 2)
Tools and Plants (1 – 1.5)
Security money is about 10% of total contract including Earnest
Money.
Security money and Earnest Money are refundable after some
time Without Any Interest.
 Types of Contract: Lumsum, unit price, cost plus contract.
 TypesofTrap:P,Q, S(Shape), Intercepting,Gully,Floor(Pur-
pose)
 Chief Engineer is theAdministrative Head of Department &
Directly responsible to the govt.
 Plastering Work:
(a) Volume is increased by 30% (if thickness 12 mm ) &
20% (if thickness 20 mm) due to uneven surface.
(b) Above calculated vol. is increased by 25% for dry vol.
calculation.
 Flooring Work:
(a) Volume is increased by 10% due to uneven surface.
(b) Above calculated vol. is increased by 50% for dry vol.
calculation.
 Cement Concrete Work: In C.C. mixture, we divide 1.52 by
sum of ratio of material and multiply it with respective
quantity ratio which will give yourespective quantity.
 Brick Work:
(a) Volume is increased by 15% due to frog filling, bonding/
jointing, wastage etc.
(b) Above calculated vol. is increased by 25% for dry vol.
calculation.
Event: It is an instant of time at which some specific milestone
has been achieved. It denotes the start or completion of an activity,
& it is represented by nodes of different shapes like rectangular,
circular, square or oval. An event does not consumes any time or
resource.
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Dummy Activity: It is an artificial activity represented by
dashed arrows which neither consumes any time nor resources.
Activity G is dummy activity. Dummies maintain the logic of
network diagram & keeps the numbering system of the network
unique.
Slack: It is associated with an event. It is the difference between
the latest allowable occurrence time & earliest expected
occurrence time of the event. It is the excess time by which
occurence of an event can be delayed without affecting the project
completion time.
Types of Slack -
(a) Positive slack ( S >0 ) - Ts
> TE
(b) Zero slack ( S = 0 ) - Ts
= TE
(c) Negative slack ( S < 0 ) - Ts
< TE
( (
(
(
 ij
Activity Name (EST, EFT)
(i) (j)
t x days (LST, LFT)

 Float is associated with An activity.
1. Total Float: It is the difference between maximum time
available & actual time required for the completion of the
activity.
2. Free Float: It is the amount of time by which an activity
can be delayed without affecting the EST of the succeeding
activity
3. Independent Float: It is the excess of minimum available
time over the required activity duration.
4. Interfering Float: It is the difference of total float & free
float of an activity. It is also equal to the slack of head event of
an activity.
Types of float -
(a) Negative total float (FT
< 0 ) - If maximum available time for an
activity is less than the activity time, then total float will be a
negative value. Such activities are called super-critical
activities.They need extra deployment of resources.
(b) Total float zero (FT
= 0 ) - If maximum available time for an
activity is equal to the activity time, then total float will be
zero. Such activities are called critical activities.In them, no
freedom of delay is allowed.
(c) Positive total float (FT
> 0 ) - If maximum available time for an
activity is more than the activity time, then total float will be
a positive value. Such activities are called sub-critical
activities.They demand normal attention but allowing them
some freedom of action.
PERT absorbs uncertainties into the time estimates for activity
& project duration. Following are 3 time estimate -
(a) Optimistic Time Estimate (to
) - It is the minimum time
required for an activity if everything occurs perfectly right without
any problems or adverse conditions developed during completetion
of the activity.
(b) Pessimistic Time Estimate (tp
) - It is the maximum time
required for an activity if everything goes wrong & abnormal
conditions prevail. It does not include possible effects of major
catastrophes like as earthquakes, flood, fire etc.
(c) Most Likely Time Estimate (tm
) - It lie in between pessimistic
& optimistic time estimate. It is time required to complete the
activity if normal conditions prevail.
 Mean time  
x :
1 2 3 n
x x x ...... x
x
n
 
 =
x
n

 Deviation (): x x
  
 Variance :
 2
2
2 x x
n n
 

  
PERT CPM
1.Probabilistic approach 1. Deterministic approach
2.Three time estimate 2. Single time estimate
3.Event oriented 3. Activity oriented.
4.Cost is proportional to time 4. Cost model is developed
5.-distribution 5. Normal distribution
6.Concept of slack 6. Concept of float
7.Critical path by joining 7. Critical path by joining
critical events critical activities.
Crashing: The process of reduction of the total project duration
along the longest path (time wise) of the network (along the critical
path to obtain the optimum project cost & optimum duration.)
Updating : It is the process of reviewing the progress of project,
execution & redrafting the network according to latest
requirements
Cost slope =
c n
n c
C C
t t


Cost
Crash
time
Optimum
time
Normal
time
Overheads
Outage cost
Indirect cost
Direct cost
Total cost
Resource Smoothing: ·In this, the total project duration is not
changed but the activities having float are rescheduled in such a
way that a uniform demand for the resources is achieved. In it, the
resources are considered to be limited & the critical path of the
project remains unchanged.
Resource Levelling: In it, the activities are so rescheduled in such
a way that maximum or peak demand of the resource does not
exceed the availability of resources. In it, the resource are
unlimited & the critical path may get changed (so project
duration may also get changed). Uniform demand of resources
is achieved.
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