MEANING OF ESTIMATION AND ITS TYPES – ALL VALUERS NEED TO KNOW

Meaning:

Estimating or estimating is the process of calculating the quantities of various items of works involved in the project. Estimates is defined as the process of calculating the probable quantities and costs of various items required in connection with work. Estimate is prepared by calculating the quantities from the dimension on the drawings for various items required to complete the project and multiplied by the unit cost of items concerned.

Necessity of Estimation

The main purpose of an estimate is to know the probable amount before the work is executed.

Estimate of a project will help us in following ways.

• It tells whether the project is suitable or not by considering the cost comparison.
• The quantity of major components of the project like cement, bricks, steel, sand etc and their cost to be entered by considering the prevailing market rates.
• It helps to invite tenders.
• It helps to monitor the contractor payment record.
• We can also check the contractor work being executed.
• The estimator’s job is to prepare estimates of building project costs.
• The success of a contractor’s business depends on the accuracy of these estimates.
• The estimator’s success will be based on his previous experience and knowledge of the construction industry.
• A contractor or estimator lacking this experience may over-, or under-estimates his project costs.

Possible Sources of Errors in Estimates

1. Mistakes in material take-offs.
2. Errors in carrying forward material from quantity sheets to summary sheets and from there to direct cost sheets.
3. Mistakes in estimating the labor time required for certain items of work.
4. Errors in estimating hourly wages of labor.
5. Failure to allow for rising costs of materials.
6. Failure to allow for delays due to breakdown of machines and acts of God (e.g. earthquakes and storms).

 Types of Estimates:

Detailed Estimates:

This consists of detailed particulars of the quantities, rates, and costs of all the materials required for satisfactory completion of a project. Quantities of all materials of work are calculated according to their respective dimensions on the drawings on a measurement sheet.

Multiplying these quantities by their respective rates in a separate sheet, the cost of all items of work are figured out individually and then summarized, i.e abstracted (which is the detailed actual estimated cost of work).

All other expenses required for satisfactory completion of the project are added to the above cost to frame the total of a detailed estimate.

A detailed estimate is accompanied by

1. Report
2. Specifications
3. Detailed drawings showing plans, different sections, Key or Index plan etc.
4. Design data and calculations
5. The basis of rates adopted in the estimate.

Such a detailed estimate is prepared for technical sanction, administrative approval and also for the execution of a contract with the contractor.

Quantity Estimates Or Quantity Survey

: This is a complete estimate or list of quantities for all materials of work required to complete the concerned project. Therefore, Quantity Survey or estimation is the art or knowledge in which materials quantity and entire cost are determined.

It is also generally known as Estimating.

Quantity survey plays a vital role in estimation and construction of any relevant project.

It will help in the determination of all related applicable costs and materials quantity so that all those factors are determined, and funds are released for the project in case if acceptable.

If funds are less, then certain alterations can be conducted so that the project can span within the fixed funds.

These alterations can be brought in the specifications of the project, or the project is conducted in stages so that the project can end within the released funds.

 

Preliminary Or Approximate Or Rough Estimate:

This estimate is prepared to decide financial aspect, policy and to give idea of the cost of the proposal to the component sanctioning authority. It should clearly show the necessity of the proposal and how the cost has been arrived at. The estimate which is prepared using any rough method to get approximate cost of the construction anticipate in a project is called approximate estimate.

Preliminary estimates are also called rough or approximate estimates, This is because they are not final—they give a ballpark idea of how much a project will cost.

 

A preliminary estimate is made at the very beginning of a project when there’s limited information available. A very early preliminary estimate is called a screening estimate and is usually based on information from similar projects done in the past,.

A preliminary estimate allows a trade or home service company to figure out the budget for a project and what to charge the client.

• For example, a roofer is asked by a client to redo the roof of his house. The roofer did a very similar project three months ago. He uses the estimate from his old project to make a preliminary estimate for his new project.

Once more information is available, a business can create a revised estimate, or detailed estimate, from the preliminary estimate.