Every construction and design company whether in the public or private sector must perform a number of management functions in order to get into and to stay in business. Any construction project goes through process of establishing the feasibility, planning, designing, administrative and technical approval, financial sanction, and finally the execution. Soon after the architectural and engineering designs of a project are completed, estimating exercise is gone through in construction parlance, an estimate is an expression of opinion or the prediction of the probable future costs of certain construction activities, usually based on some data having an acceptable degree of reliability. The construction/industry embraces many types of construction work, all of which can be classified under two broad headings, namely heavy construction which includes bridges, dams, roads, mills and the like; and building construction which includes residential and non-residential construction. In this unit, emphasis will be on the latter with some coverage given to roads. However, most of the principles illustrated will be applicable to both types.
It is important to recognize right at the beginning of this study, the importance of estimating in the affairs of a construction- or design company. The success of the business will be directly proportional to the quality of the estimating process and the reliability of its results. All construction activities are divided into two categories, viz.
- those that occur outside the company and therefore beyond its significant control, and
- those that occur within the company and therefore within its direct control, it seems only prudent to remove as much of the risk as possible from all internal activities, not least of which is the activity of estimating.
Estimating can be defined as the formation of an approximate judgement or opinion regarding the value, amount, size, or weight of something. More precisely, it refers to careful and correct measurement of various quantities involved in a construction project as reflected in contract documents and drawings and the subsequent calculation and application of accurate unit prices to these quantities. The purpose is to produce the probable total costs of the work to be done. The estimating is generally carried out component-wise for a large construction project and individual costs of components are added up to arrive at the total cost of a project.
A well prepared estimate forms a sound basis for
- the efficient management of resources - such as money, men, materials and machines,
- entrusting the works for execution to contracting agencies on a competitive basis,
- identifying the needs for alternative solutions to achieve economy in construction,
- scheduling and monitoring of the project time and cost, and
- submission of tenders or bills by contractors to user organisations.
After studying this unit, you should be able to
- understand the concept of "components" of a project or a structure from the point of view of estimating,
- test the identified component for quantification,
- conceptualize the principles and methods of measurement and methodology of pricing,
- choose approximate units of measurements for each component and decide on levels of accuracy,
- determine the unit cost (rate) of comprising material, labour and equipment for the given specifications of the identified component,
- comprehend the complete approach of preparation of an estimate of a structure/project, and
- describe the principles and methods of approximate estimates and distinguish between detailed and approximate estimates.
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