ESTIMATE Theory For Exams Point Of View And Calculating Concept
Estimate can be defined as the procedure or method of working out the quantity & then calculating the cost at suitable rates. Estimating is the technique of the calculating or computing the quantities of particular work or project.
Need/Purpose of Estimation-
1. Estimate gives an idea of approximate cost of work.
2.To know the approximate quantity of various materials & labour required.
3. To have an idea about the time of completion of the work/project.
4. For invite the tenders, quotations & to arrange the contract.
5. To justify the investment from benefit-cost ratio.
6. An estimate required for an existing property is needed to valuation.
7. It helps in financial planning to once before going to construction.
8. It is also required to control the expenditure during the execution of work.
Types of Estimate-
At this stage, the students would have understood the meaning and importance of the estimate. The different types of estimates are used at the different stages of the construction. Based on the details and accuracy, estimates are classified into the following two types:
1. Preliminary Estimate/ Approximate Estimate/Rough Estimate
(a) Plinth Area Rate Estimate
(b) Cube Rate Estimate/Cubical Contents Estimate
(c) Service Unit Estimate/Unit Base Estimate
2. Detailed Estimate
(a) Supplementary Estimate
(b) Revised Estimate & TRICKS
(c) Combination of Supplementary Estimate & Revised Estimate
(d) Annual Repair or Maintenance Estimate
(e) Complete Estimate
Method/Procedure of Estimating
Estimating involves mainly 3 following operations-
1. Analysis Drawing & Project work.
2. Preparing Detailed Estimate.
3. Calculating the rate of each unit of work and items & Preparing Abstract of Estimate.
Data required for preparation of an Estimate
To prepare an Estimate for a project,
following data are required-
1. Detailed Drawings
2. Specifications
a) General Specifaction or Brief Specification
(b) Detailed Specification
3. Schedule of Rates
PRELIMINARY/APPROXIMATE ESTIMATE
Approximate estimate is made to find out an approximate cost in a short time without taking out actual quantity.
Preliminary estimate required various aspect of work or project to decide financial position & policy for administrative approval.
It is prepared from practical knowledge cost of the similar works.
It contains the cost of all important items such as Cost of land, Cost of each building material, Water supply & sanitary, Electrification & Other services.
The accuracy of approximate estimate depends upon the judgment skill & experience of the estimate.
Uses of Preliminary Estimation
1. To give rough idea of the probable cost.
2. For Administrative approval.
3. For Valuation & Rent.
Plinth Area Rate Estimate
This estimate is prepared on the basis of Plinth Area of building plinth area estimate is prepared by finding the plinth area of the building & multiply by the plinth area rate.
Cost of Building
= Plinth area ×Plinth area rate
Cube Rate Estimate/Cubical Contents Estimate
It is prepared on the basis of cubical content of the building i.e. Length, Width/Breath & Height.
Cost of Building
= Total cubic content × Cost per cube
Service Unit Estimate/Unit Base Estimate
Each building constructed to some purposes e.g. "Hostel" is designed to certain number of room each "Room" is then considered as service unit of the Hostel.
Cost of Building
= No. of service unit ×Rate of service unit
METHODS OF DETAILED ESTIMATE (TAKING OUT QUANTITIES)
The Following methods are used for taking out quantities-
1. English Method
2. P.W.D. Method
1. English Method
The quantities of the various items are worked out and a measurement
or dimension form and then quantities of identical items are grouped together and written on an abstract form.
1. Taking off Dimensions from Drawing
2. Grouping them
3. Billing
Column (1) is called the Timesing column. Column (2) is called Dimension column.
Column (3) is called the Squaring column. Column (4) is called the Description column. In which, the brief description of the item is written. The right-hand side of this column is
used for rough work and is known as the waste. In the Dimension column Length, Breadth/Width & Height/Depth are written in
sequence in vertical direction. The multiplication giving the final quantity is then entered in the squaring column.
Features of the English method-
1. The quantities are found out in the sequence of measurements, irrespective of items of work and sequence of execution
2. The grouping is a separate process and it is followed along with the process of billing on
the abstract form.
3. The chances of omitting any measurements are reduced
4. The method is lengthy and it requires more time.
2. P.W.D. Method-The PWD Method
is commonly adopted in our country for preparation of Detailed Estimate. In this method taking out the quantity or prepared detailed estimate on following steps-
1. Quantity calculation is done on Measurement Sheet. TECH & TRICKS
2. Billing is done on the Abstract form as in case of the English method.
Features of P.W.D. method
1. The quantities are found out in the sequence of execution, irrespective of the sequence of measurements.
2. The grouping process is eliminated in the sense that the measurements are directly
grouped on the quantity sheet.
3. There are chances of missing some measurements.
4. The method is easy and it requires less time.
Taking Out Quantities
The procedure by which quantities of the various items in a particular structure are worked out is known as taking out quantities, The quantities are obtained by studying in detail the drawings of the structure.
Quantities are worked out by any one of the Methods-
1. Long Wall Short Wall Method
2. Center Line Method
DETAILED ESTIMATE
Detailed estimate includes quantities & cost of everything required for satisfactory completion of work & this is the best and most reliable estimate that can be made. Detailed estimate prepared in 2 stages.
1. Measurement Sheet (Quantity)
2. Abstract Sheet (Cost)
Uses of Detailed Estimation
1. To know the accurate cost of the Project/Work.
2. Quantities of various items of work are known.
3. To know the cost of each items of work/project.
4. To invite tender for a work.
Types of Detailed Estimate
(a) Supplementary Estimate
(b) Revised Estimate
(c) Combination of Supplementary Estimate & Revised Estimate
(d) Annual Repair or Maintenance Estimate
(e) Complete Estimate
(a) Supplementary Estimate
It is a detailed estimate for additional items of the work needed were not included in original estimate. While work is in progress some additional work may be thought necessary for development of the project which not forseen when the original estrimate was formed, an estimate is then prepared to cover up all such works
(b) Revised Estimate
It is a detailed estimate which is prepared one of the followingparameters-
1. When oroginal sanctioned estimate exeeds by more than 5%.
2. Expenditure on work exceeds or likely to exceed the Administrative approval by more than 10%.
3. There are material deviation. In revised estimate a comparative statement is prepared indicating variation of each of work, cost & rate under originl and revised cost side by side showing excess or saving & reason for variation.
(c) Combination of Supplementary Estimate & Revised Estimate
If before or after the executionI of work it is found that the original estimate is excessive then competent authority sanctions a revised estimate & informs accountant generals also.Revised estimate is required due to changes of rate or quantitry of material so an addition or revison of darwing is neccesary. Supplementary estimate is required due to some new works or change of design so addition or revision of drawing may be neccesary.
(d) Annual Repair or Maintenance Estimate
It is a detailed estimate which is prepared for the items which is requires renewal, replacement, repaired etc. Annual repaired cost of building is 1-1.5% of the original cost of the building.
