LEARN : Estimating and costing,Data required for preparation of estimate,Definition of Estimating,Complete Set of Detailed Drawings,Specifications of Items of Works,Prevalent Rates of Items of Construction,Standard Mode of Measurement,Details of foundation strata likely to encounter.,The exact location of the work site.,The physical condition of the work site.
Introduction to Estimating and Costing
Before any engineering project is to be constructed, it is necessary to know its estimated cost to ascertain whether the required funds can be made available for its completion or not.
If the funds available are more than the estimated cost of the work, the execution of the work can be started.
If, however, the available funds are less than the estimated cost, then either the work may be executed in parts or its specification can be altered to bring down its cost within the available funds.
The actual cost of construction (which will be known after its completion) should not exceed the estimated cost of the work.
Definition of Estimating
To know the cost of the proposed work, it is required to prepare a detailed estimate of the proposed work.
An estimate is a probable cost of the work, arrived by mathematical calculations based on the measurement of quantities of various items of work involved in the work.
The quantities of the various items of work are then multiplied by the present market rates for those items to arrive at the cost of all such items.
Summation of costs of all such items gives the total estimated cost of the work.
Data required for preparation of estimate:
In order to prepare a detailed estimate of the proposed work, the following information is required:
(i) Complete Set of Detailed Drawings:
In order to work out the quantities of various items of work, a complete set of detailed drawings consisting of plan, elevation, sections and foundation details etc. is required.
The relevant dimensions i.e. length, breadth, depth or height of the items, whose quantities are to be worked out, can be measured from such drawings.
(ii) Specifications of Items of Works:
The rate of an item depends upon the specifications of the work.
Specifications provide information regarding type of construction, quality of materials, proportion of mixes, manner in which the work is to be executed, etc.
(iii) Prevalent Rates of Items of Construction:
After the quantities of various items of work involved are calculated, they are to be multiplied by the current market rates of those items.
The Government department such as Buildings and Communication, Irrigation and Power Department prepares schedule of rates for all items of work pertaining to the department for a district or area, on the basis of analysis of rates of items.
A booklet called ‘District Schedule of Rates’ (D.S.R) is available for sale in such Government Organisations.
(iv) Standard Mode of Measurement:
I.S. 1200 has specified the procedure of measurement of various items of work, standard deductions to made if any, the accuracy of measurement etc. and is to be followed while preparing estimates.
(v) Details of foundation strata likely to encounter.
(vi) The exact location of the work site.
(vii) The physical condition of the work site.
It is usual practice to enclose a brief report containing information about the proposed work i.e. project as regards the following:
• The history and necessity of the proposed work.
• The exact location and condition of the work site.
• Details of soil strata at the site.
• The total cost of the proposed work.
• Source of the finance required for the completion of the work.
• Probable period of completion of the work.