8 types of Estimation and their Practical Uses

Articles > 8 types of Estimation and their Practical Uses

Introduction:

The process of calculating the approximate amount of the project before construction of the work is known as Estimation.Estimation of a project includes the cost of labour, carriage and materials differently

In case of cost of labour, it is done based on the skills of the labour. There are two types of labours-

Skilled labours (carpenters, Blacksmith, Masons etc)
Unskilled labours (coolies,bhisti etc)

The carriage cost basically includes the cost of transportation, for eg. Dumpers that are required in the site, bulldozers etc.

The material cost includes the materials required for the project like brick,stone,sand,steel,cement etc.

Apart from the above mentioned costs there are certain other costs which include the water and electricity charges, health care costs of the workers at site, maintenance costs etc.Estimation if not done properly can give an amount which is more than the actual required cost of the project known as Overestimate and sometimes the amount estimated can be less than the actual amount required for the project known as Underestimate.

Purpose of estimation:

Fig. Purpose of estimation

Courtesy: Wikipedia

When a project is started to understand the amount of the materials required and other items required ie. for a proper assessment of the project estimation is required. Before starting of the project the estimation has to be done to know the rough cost of everything. Also in order to access the materials required for the project and to have proper idea about the materials estimation is required.During estimation the time planning of the project is to be prepared, from this a clear knowledge about the duration of the project can be made. Hence estimation is highly necessary for any kind of project, the following are the main purpose of estimation:

To visualise the different aspects of the job
To access amount of materials and cost
Knowing the time limit of the project?
To know the approximate count of labours required for that particular project
Having a proper idea of the construction equipments to be used

Types of Estimation:

Preliminary or approximate estimation: Gives an approximate idea of the cost of the project to the sanctioned authority. It is also known as abstract cost estimate or approximate cost estimate or budget estimate.

Unit Rate Estimate: All the cost of a unit quantity of work such as per km for a highway, per litre for water tank etc are prepared at first and the estimate is prepared by multiplying the cost per corresponding units by the number of units in the structure.
Plinth Area Estimate: Plinth area is the area of external dimensions of the building excluding plinth offset. The estimates are prepared on the basis of the plinth area if various building proposals are to be considered.
Cube Rate Estimate: Estimation is done on the basis of cubic content of the building. The Cubic Content of the building is the Overall area multiplied with the height of the building.

Detailed Estimate: Accurate form of estimate which is prepared after getting administrative approval on the rough cost estimate. This includes the quantities and cost of everything required for satisfactory completion of the project. In this form of estimate an additional amount of (3 to 5% of the total estimate cost) is added for contingencies as miscellaneous expenditure. The details estimate include

Report
Specifications
Detailed drawings showing planes, elevations, sections etc
Design data calculations
Basics of rate adopted in the estimate

Annual Repair Estimate: Also known as annual maintenance cost which is prepared to know the maintenance cost of the building and roads. In order to keep the building and roads in perfect condition, annual repairs should be carried out. In case of buildings white washing, oiling, paintings of doors and windows,cement plaster repairs,repairing of floors etc.The annual repair amount should not exceed 45% of the capital cost of the building.
Revised Estimate: When the sanctioned amount exceeds by more than 5% either due to rates being found insufficient or due to sudden increase in cost of material or cost of transportation etc.,a fresh new estimate is prepared which is called a revised estimate. A comparative statement of the last page of the estimate is attached which includes the reason for the increase in cost in case of each item.
Supplementary Estimate: Supplementary estimate is prepared when some additional work becomes necessary for the project which was earlier not included in the detail project. A new estimate is prepared in addition to the original ?anctioned estimate prepared describing the additional works which is called supplementary estimate.
Complete estimate: An overall estimate of the items which are related to the project in addition to the detailed estimate. The complete estimate includes

Cost of land
Cost of legal expense between owner and contractor
Cost of main contract of the material and supervision
Contingency 5% for centre work
Engineering fee which includes - cost of preparation of drawing, design, estimate etc and site supervision cost
Fee for water and electricity
Miscellaneous

Conclusion:

Due to its immense use,estimation is the first and foremost step in any civil engineering construction because without estimation the project cannot be started and hence the knowledge of proper estimation is highly essential and the various types of estimates as discussed above must be used according to the situation required. Estimation can be defined as the skeleton of the project because without having a proper knowledge about the project, the work cannot be started.

Reference:

Wikipedia, “Estimation”
Wikipedia, “Types of estimation”
Book- B.C.Punmia

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