04. estimating, gantt chart and s-curve preperation

7/29/2019 04. Estimating, Gantt chart and S-Curve Preperation

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ESTIMATING, GANTT CHART

AND

S-CURVE PREPARATION

RAMON RELLITA TAN, CE, MPM

Asst. City Engineer


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A)

ESTIMATING:

Estimating is a calculation of the quantities of variousitems of work, and the expenses likely to be incurred thereon.The total of these probable expenses to be incurred on the

work is known as estimated cost of the work. The estimatedcost of a work is a close approximation of its actual cost. Theagreement of the estimated cost with the actual cost willdepend on accurate use of estimating methods and correctvisualization of the work, as it will be done. Importance ofcorrect estimating is obvious. Under-estimating may result in

the client getting an unpleasant shock when tenders areopened and drastically modifying or abandoning the work atthat stage. Over-estimating may lose the engineer orestimator his client or his job, or in any case his confidence.


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PURPOSE OF ESTIMATING:

Thepurpose of estimating is to give a reasonablyaccurate idea of the cost. An estimate isnecessary to give the owner a reasonablyaccurate idea of the cost to help him decidewhether the work can be undertaken as

proposed or needs to be curtailed or abandoned,depending upon the availability of funds andprospective direct and indirect benefits.


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TYPES OF CONSTRUCTION

ESTIMATES:

There are several kinds of estimating techniques;these can be grouped into two main categories.

1. APPROXIMATE ESTIMATES

2. DETAILED ESTIMATES


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APPROXIMATE ESTIMATES

An approximate estimate is an approximate orrough estimate prepared to obtain anapproximate cost in a short time. For certainpurposes the use of such methods is justified.


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DETAILED ESTIMATES

A detailed estimate of the cost of a project isprepared by determining the quantities and costs of

every thing that a contractor is required to provideand do for the satisfactory completion of the work. Itis the best and most reliable form of estimate.

Detailed Estimate of Construction Cost a forecastof construction cost prepared on the basis of adetailed analysis of materials and labor for all itemsof work, as contracted with an estimate based oncurrent area, volume or similar unit cost.


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QUALIFICATIONS OF AN ESTIMATOR

A good estimator should possess the following qualifications:

1. A thorough understanding of architectural drawings.2. A sound knowledge of building materials, construction

methods and customs prevailing in the trade.3. A full of information collected or gained through

experience in construction work, relating to materialsrequired, hourly output of workers and equipments,

overhead expenses and costs of all kinds.4. An understanding of a good method of preparing anestimate.

5. A systematic and orderly mind.6. Ability to collect, classify and evaluate data that would be

useful in estimating.


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IMPORTANT ITEMS TO BE CONSIDEREDIN ESTIMATING:

MATERIALS:

LABOR:

EQUIPMENT:

TIME:


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MATERIALS:

From the estimate of a work it is possible todetermine what materials and in what quantitieswill be required for the work so that thearrangements to procure them can be made.


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LABOR:

The number and kind of workers of differentcategories who will have to be employed tocomplete the work in the specified time can befound out from the estimate.


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EQUIPMENT:

An estimate will help in determining amountand kind of equipment needed to complete thework.


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TIME:

The estimate of a work and the past experienceenable one to estimate quite closely the length oftime required to complete an item of work or thework as a whole.


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DOCUMENTS REQUIRED INESTIMATING

Architectural Plans

Specifications (separate for building)

Red Book (specification for Roads and Bridges)

National Building code

City/Municipal Ordinance


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COST INVOLVED IN ESTIMATINGA-Direct Costs (for Building) B-Direct Costs (for Roads)

a. Mobilization a. Mobilizationb. Site Preparation b. Clearing and Grubbingc. Layout c. Roadway Excavationd. Earthworks (excavation & backfill) d. Embankmente. Structural Works e. Line Ditch

f. Architectural Finishes f. Sub-Base Courseg. Plumbing Works g. Base Courseh. Electrical Works h. Slope Protectioni. Mechanical Works

Indirect Costsa. Contingencies

b. Engineering Supervisionc. Contractors Profitd. Vate. City Tax


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B)

GANTT CHART

AGantt Chart is a type of bar chart thatillustrates a project schedule. Gantt charts

illustrate the start and finish dates of theterminal elements and summary elements of aproject. Terminal elements and summary

elements comprise the work breakdownstructure of the project.


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The Bar Chart is derived from the Gantt Chart.It represents a graphic record of the projects

progress. It gives detail of the work along withthe time schedules from the beginning date tothe completion date of each activity. Thus, itshows the day-to-day status of every activity, the

comparison between the actual accomplishmentand the corresponding work schedules, anddistribution of manpower, materials, equipmentand cash flow.


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The Bar Chart has the distinct character ofbeing easily understood by non-technical people.

However, its simplicity becomes its weakness asa control tool because it lacksthe detailedbreakdown of the different activities particularly

their proper and operational dependencies. Thisbuilt-in weakness prevents the Bar Chart frombeing a fully effective updating instrument.


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C)

S-CURVE

An S-Curve is a well known projectmanagement tool and it consists in a display of

cumulative costs, labor hours or other quantitiesplotted against time. The name derives from theS-like shape of the curve, flatter at the beginning

and end and steeper in the middle, because thisis the way most of the projects look like.


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An S-Curve represents the actual workaccomplishment as against the work schedule,

visually identified with a sloping line originatingfrom the bottom left zero percent (0%)accomplishing going up to the upper right, 100%

accomplishment.


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Looking at the S-Curve line the reader canreadily see the project status at a given time

whether it is ahead of or behind schedule. Anupdated S-Curve immediately presents thepositive and negative variance ofaccomplishment and as such the timely remedialmeasures can be applied.


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GOOD AFTERNOON

THANK YOU

04. estimating, gantt chart and s-curve preperation

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