Transcript
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DR SHAIFUL AMRI
FKA UTM SKUDAI
Principles of Analytical Estimating
• To analyse something is to break it down into itsconstituent parts and study each part in detail.Therefore analytical estimating involves theanalysis and costing of construction resources toproduce an estimate.
• The production of an estimate normally involvesthe calculation of unit rates i.e. the cost of asquare metre of brickwork, a cubic metre ofconcrete or a metre of skirting (as found in a Billof Quantities).
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DR SHAIFUL AMRI
FKA UTM SKUDAI
• Analytical estimating is therefore the most
accurate form of estimating as each resource
and unit rate is analysed and costed
individually. This form of estimating is used for
pricing contracts with bills of quantities,
specifications and drawings or where the
contractor has measured and prepared their
own quantities of work.
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DR SHAIFUL AMRI
FKA UTM SKUDAI
• Tukang
– Skilled workers; craftmen; highly paid per hour
• Kepala (Mandur)
– Leader in the subcontracted work
• General labour
• Angkatap buruh
– Rate of doing certain type of work (e.g. hour permeter3
• requires determining the number of labor
hours to do a specific task and then applying a
wage rate.
– 1 labor hour = 1 labor working 1 hour
• requires knowing the quantity of work to beplaced and the productivity rate for the
specific crew.
• The productivity rate is often expressed as a
number of labor hours per unit of work.
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DR SHAIFUL AMRI
FKA UTM SKUDAI
• The productivity rates can come from a
number of sources, but the most reliable
source is historical data. The advantage of
historical data is that it reflects how a
particular company’s personnel perform the
tasks.
Productivity rate = Labor hours ÷ Quantity of work
Example of good historical data:
Type of work — 8'' × 8'' × 16'' Concrete Masonry Units
(CMUs)
Quantity of work—1,700 square feetLabor cost—RM6,987
Labor hours—170 labor hours
Productivity rate = 170 labor hours ÷ 1,700 ft2
= 0.1 labor hours per sf
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DR SHAIFUL AMRI
FKA UTM SKUDAI
How to apply?
Labor hours = Quantity takeoff x Productivity rate
• The productivity rate derived from historical data is for the
average or standard conditions
• On many occasions, the project that is being bid deviates from
these standard conditions.
Adjusted labor hours = Labor hours x Productivity factor
Variables for Productivity Factor
• Availability and Productivity of Workers
– Number & skill factors
• Climatic Conditions
– Cold, hot, winds, rain, snow, etc.
• Working Conditions
• working space, storage space, high-rise etc.
• Efficiency
– averaged 30 to 50 minutes per hour
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DR SHAIFUL AMRI
FKA UTM SKUDAI
• Once the average crew wage rate has been
found, it can be multiplied by the number of
labor hours to determine the labor costs
Labor cost = Adjusted labor hours x Weighted average
burdened wage rate
In addition to the actual cost of the material the
estimator must also consider:
• Transportation costs
• Unloading and Stacking costs
• Materials movement on site
• Extra Materials to compensate for:
– Wastage; Allowance in BQ; Loss in consolidation,
shrinkage etc.
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• “The equipment must pay for itself.”
• If the cost can be charged off to one project or
other proposed uses of the equipment, it will
pay for itself and should be purchased.
– For example, if a piece of equipment costing
$15,000 but will save $20,000 on a project, it
should be purchased
For idling plants (a few weeks):
1. What will be done with it?
2. Will it be returned to the storage/garage?
3. Is there room to store it on the project?
4. If rented, will it be returned so that the rental
charge will be saved?
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DR SHAIFUL AMRI
FKA UTM SKUDAI
• Non-Mechanical Plant
– Basic items of plant including wheel-barrows,
hosepipes, spades, trestles, scaffolding, small
powered hand tools etc
– With the exception of scaffolding and one or two
other items it is virtually impossible to allocate the
cost of non-mechanical plant items to a contract,
let alone to a specific unit rate (e.g. mostly may beused on several contracts in its lifetime).
• Non-Mechanical Plant
– The cost may be included in overhead charges as a
percentage, as a lump sum in the preliminaries bill
or, more accurately, on longer contracts a list of
non-mechanical plant items is prepared, costed
and included in the contract sum.
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DR SHAIFUL AMRI
FKA UTM SKUDAI
• Non-Mechanical Plant
– Peranca (scaffolding)
– Kain terpal (trapauline)
– Kotak pengukur (gauge boxes)
– Tangga (ladders)
– Kereta sorong (wheel barrows)
–
Perkakas (tools) – Pelentur besi (bending machine)
• Mechanical Plant
– Equipment that is required throughout the project
is included under equipment expenses, because it
cannot be charged to any particular item of work.
(e.g. material-handling JCB and forklifts.)
– Mechanical plant such as excavators, lorries,
dumpers, mixers, etc. can be very expensive.
Contractors may buy, hire or lease.
– The purchase of plant must be viewed as an
investment on which a return is required.
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DR SHAIFUL AMRI
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• Mechanical Plants
– Lorry
– Excavator
– Bulldozer
– Concrete mixer
– Vibrators
–
Compressors – Rollers
• Possible costs
– cost of hiring or depreciation
– maintenance & repair
– fuel
– operator & labor costs
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DR SHAIFUL AMRI
FKA UTM SKUDAI
• The amount of money added to the total
estimated cost of the project.
• Determined by a number of factors largely
outside the remit of an estimator. However, in
larger companies the senior or managing
estimator may be a member of the
management team. In smaller companies, theestimator may be a director. In both cases
they may make commercial decisions
regarding profit margins.
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1
Factors affecting profit levels are:
• Market forces of supply and demand
• Amount of competition
• Who the competitors are
• Size / Value of contract
• Risk involved in contract
• Interest rates.
A few typical approaches are listed as follows:
1. Add a percentage of profit to each item as it is
estimated, allowing varying amounts for the
different items; for example, 8 to 15% for
concrete work, but only 3 to 5% for worksubcontracted out.
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DR SHAIFUL AMRI
FKA UTM SKUDAI
A few typical approaches are listed as follows:
2. Add a percentage of profit to the total price
tabulated for materials, labor, overhead, and
equipment. The percentage would vary from
small jobs to larger jobs (perhaps 20 to 25%
on a small job and 5 to 10% on a larger one),
taking into account the accuracy of the takeoffand pricing procedures used in the estimate.
• Look at the profit then discuss the risks.
• It is far better to bid high enough to cover the
risks than to neglect the risks, bid low, and
lose money. Sometimes a tendency to “need”
or “want” a job so badly that risks arecompletely ignored. If a project entails
substantial risk and profit is questionable, do
not bid.
• Remember, construction is a “business”..
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