estimating and costing- brief note

Srinivasan

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Staff member
Sep 7, 2017
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1.1 Definition of estimate and its different types

For all engineering works, it is required to know beforehand the probable cost of construction known as “Estimated cost” .If the estimated cost is greater than the money available, then attempts are made to reduce the cost by reducing the work or by changing the specifications.
In preparing an estimate, the quantities of different items of work are calculated by simple measurement methods and from these quantities the cost is calculated.

1.1.1. What is an estimate?
 An estimate is a calculation of the quantities of various items 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.
 Estimating is the technique of calculating or computing the various quantities and the expected Expenditure to be incurred on a particular work or project. The following requirements are necessary for preparing an estimate:
a) Drawings like plan, elevation and sections of important points.
b) Detailed specifications about workmanship & properties of materials etc.
c) Standard schedule of rates of the current year.
i. Need for estimation and Costing
• Estimate gives an idea of the cost of the work and hence its feasibility can be determined i.e whether the project could be taken up with in the funds available or not.
• Estimate gives an idea of time required for the completion of the work.
• Estimate is required to invite the tenders and Quotations and to arrange contract.
• Estimate is also required to control the expenditure during the execution of work.
• Estimate decides whether the proposed plan matches the funds available or not.

 Estimating involves the following operations:

1. Takingoutquantities :
In the first step of taking out quantities, the measurements are taken off from the drawings and entered on measurement sheet or dimension paper. The measurements to be taken out would depend upon the unit of measurement.
2. Working out: this step involves squaring and abstracting:
All calculations are done in these stages and every entry transferred should be checked

by another person to ensure that no mathematical or copying error occurs, there include:
• Calculating the rate of each unit of work
• Preparing abstract of estimate.

ii. Data required in preparation of an estimate :

In order to prepare a detailed estimate the estimator must have with him the following data:

1. Drawings (plans, elevations, sections etc): If the drawings are not clear and without complete dimensions the preparation of estimation become very difficult. So, it is very essential before preparing an estimate.
2. Specifications:

a) General Specifications: This gives the nature, quality, class and work and materials in general terms to be used in various parts of work. It helps no form a general idea of building.
b) Detailed Specifications: These give the detailed description of the various items of work laying down the Quantities and qualities of materials, their proportions, the method of preparation workmanship and execution of work.
3. Rates: For preparing the estimate the unit rates of each item of work are required:
1. for arriving at the unit rates of each item.
2. The rates of various materials to be used in the construction.
3. The cost of transport materials.
4. The wages of labour (Payment for labor or services to a worker, especially remuneration on an hourly, daily, or weekly basis or by the piece), skilled or unskilled of masons, carpenters, Maz door, etc.
iii. Complete estimate
Most of people think that the estimate of a structure includes cost of land; cost of materials and labour, but many other direct and indirect costs included and are shown below
The complete estimate of a project or building structure should include all items of expenditure from the beginning up to the end.
iii. Purpose of Estimating:
1. To give a reasonably accurate idea of the cost:
An estimate is necessary to give the owner a reasonably accurate idea of the cost to help him decide whether the work can be undertaken as proposed or needs to be curtailed or abandoned, depending upon the availability of funds and prospective direct and indirect benefits. For government works proper sanction has to be obtained for allocating the required amount. Works are often let out on a lump sum basis, in which case the Estimator must be in a position to know exactly how much expenditure he is going to incur on them.
2. Estimating Materials:
From the estimate of a work it is possible to determine what materials and in what quantities will be required for the work so that the arrangements to procure them can be made.
3. Estimating Labor:
The number and kind of workers of different categories who will have to be employed to complete the work in the specified time can be found out from the estimate.
4. Estimating Plant:
An estimate will helps in determining amount and kind of equipment needed to complete the work.
5. Estimating Time:
The estimate of a work and the past experience enable one to estimate quite closely the length of time required to complete an item of work or the work as a whole.
Whereas the importance of knowing the probable cost needs no emphasis, estimating materials, labor, plant and time is immensely useful in planning and execution of any work.
iv. Qualities of a good estimator:
Estimator must have the following qualities:
1. Estimator has ability to read and interpret drawings and specifications.
2. Estimator should have good communication skills.
3. He should have knowledge of basic mathematics.
4. He should have patience.
5. Estimator should have good understandings of fields operations and procedure.
6. He should have ability to visualize three dimensional projects by looking at the drawing.
7. He should have ability to interpret the risks and then neutralize as much as possible.
8. He should have good organizational ability. So that he can communicate his estimate in logical and clear presentation to the client.
9. He should have ability to prepare construction schedule.
10. He should have ability to anticipate all construction steps in building projects.
11. He should have good understanding of labor productivity and equipment performance.
12. He should have ability to use the construction company’s job costing system.
13. He should have ability to think alternate methods of construction.
14. Estimator should have ability to develop strategy for being successful in bidding and negotiation phase of the project.
15. Estimator should have ability to meet deadlines and still remains calm.
16. He should have a solid load of ethics.
17. Estimator should have understanding of contractual relationship.

v. LUMP-SUM:

While preparing an estimate, it is not possible to work out in detail in case of petty items. Items other than civil engineering such items are called lump sum items or simply L.S. Items.
The following are some of L.S. Items in the estimate:
• Water supply and sanitary arrangements.
• Electrical installations like meter, motor, etc.,
• Architectural features.
• Contingencies and unforeseen items
• Communication and transportation.
In general, certain percentage on the cost of estimation is allotted for the above L.S. Items
Even if sub estimates prepared or at the end of execution of work, the actual cost should not exceed the L.S. amounts provided in the main estimate.
Contingencies: indicates incidental expenses of miscellaneous character which cannot be classified under any distinct item sub-head, yet pertain to work as whole. Provision for contingencies 3% to 5% of estimated cost, is made in the estimate to cover the miscellaneous petty expenditures which do not come under
 

Srinivasan

Administrator
Staff member
Sep 7, 2017
850
989
mumbai
#3
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