WHAT IS ESTIMATING AND COSTING ?

ESTIMATING AND COSTING

Introduction :

For all engineering work it is necessary to know the probable cost of construction therefore estimation is important. In estimation the quantities of different item of work are calculated and from these quantities cost is calculated. Accuracy in estimation is very important. A detailed estimate is prepared by using measurement sheet and abstract sheet.

Etimating:

It is the process  of calculating the quantities and cost of the various items required in construction with the work for its satisfactory completion.

Purpose of Estimating : 

1. To know the approximate cost of proposed work.
2. To obtain administrative approval and technical sanction.
3. To know requirements of tools, plants and equipements.
4. to fix up the completion period.
5. To draw up a construction schedule and programe.
6. Valuation to know value of proprty.
7. To invite tenders.
8. To keep control over expenditure during construction.

Costing:

It is the process of determining the actual cost of the work before the execution of work.

Purpose of Costing : 

1. To arrange the finance for proposed work.
2. To know the probable cost of project before the execution
3. for valuation of existing property.
4. To know the cost of various item, well in advance, to be constructed.

Types of Estimate:

Basically all estimate are more or less approximate because the exact cost of construction will be know after the completion completion of work but detailed estimate will give fairely accurate cost.

1) Approximate Estimates or Preliminary Estimate:

It is rough estimate prepared to know the approximate cost of work in short time. In this type of estimate, estimate is prepared on the basis of actual cost of similar existing structure. The various factors of comparisons may be cubic content, per capita, per km, service unit etc. These are useful cost at initial stages to decide the feasibility of work. to prepare approximate estimate less skill and time is required.

Purpose of approximate estimate:

1. To know feasibility of project.
2. To know project duration.
3. To obtain administrative approval.
4. For insurance and tax schedule
5. For planning the project.
6. to know benefit cost ratio.
7. Investment - To see whether investment is justified or not.

Types of approximate estimate:

1. Plinth area method
2. Cubic content method 
3. Service unit method
4. Approximate quantities method
5. Typical bay method

2) Detailed Estimate:

It is prepared by finding out actual quantities of different items of work and then it is multiplyed in corresponding rates.

Quantities of all item of work shall be calculated from their respective dimensions from the drawing on a measurement sheet. Multiplying these quantities by their respective rates in a separate sheet, the cost of all item are worked out individually and then abstracted. All other expenses required for satisfactory completion of the project are added to the above cost to know the total of a detailed estimate. This is the best and most accurate estimate that can be prepared.

Purpose of detailed estimate

1. Technical sanction.
2. Administrative approval.
3. The execution pf a contract with with the contractor.
4. Framing and inviting tender.
5. Accurate idea of cost of construction.
6. To know materials required.
7. To know various labours required.
8. To know project duration.
9. To determine earnest money and security deposit.

Types of detailed estimate

1. Revised estimate
2. Supplementary estimate
3. Revised and supplementary estimate
4. Maintenance and repair estimate.

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Other Useful Links

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Click Here To Download Civil Engineering Gate Study Materials

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