How S-curve help to Contractor

(Figure 01)

In many contracts, the owner requires the contractor to provide an S-curve of his estimated progress and costs across the life of the project. This S-shaped of the curve results because early in the project, activities are mobilizing and the expenditure curve is relatively flat. As many other activities come on-line, the level of expenditures increases and the curve has a steeper middle section. Toward the end of a project, activities are winding down and expenditures flatten again (Figure 01). The S-Curve is one of the most commonly techniques to control the project costs.

An S-curve can be useful as a means through which control of work can be affected. The minimum necessary information for this purpose id illustrated in figure 01. The cumulative budgeted expenditure that is the cost to be incurred by a contractor in construction is represented by the full-time of S-curve. The actual expenditure curves show the current cumulative cost at any point in time up until the present or time now.

The actual expenditure just exceeds the budgets time now in the figure 01. However, it may or not represent better progress than that expected. From the figure 01, the conclusion is that over budget has been incurred than was budgeted at time now. The progress is behind the budget. Cost is expended at a faster rate than budget and may cause cash flow problems.

Thus, overall attention needs to be paid to the efficiency of the work methods, productivity and financing. From figure 01, it will be seen that a forecast of expenditure to complete the work shows a likely final overrun, but will cause delay in completion of the project. The vertical axis of the S-curve graph is usually expressed in units of money. However, it is also can be expressed in terms of work content, for example, cubic meters of excavation, tones of structural steel erected, or man hours of work content for a particular operation or a group of activities.

For a project with a number of activities, it is much easier to use an S-curve for each one, to ensure that progress advances as require. It is practicable and useful to use a scale of percentages, the whole of the particular work under consideration expressed as 100 percent in addition to using units of work on the vertical scale. These types of scales obviate the need to change the total quantity of work involved when variation to it is scope occur.