Lags and Leads

A lag in a schedule denotes the passage of time between two activities. Lags simply delay a successor activity—no effort or resources are associated with this passage of time. A common example of the use of a lag is the passage of time to allow concrete to cure, as in figure 17. The forms on the basement walls cannot be stripped until the concrete cures. While other work may occur in parallel in other parts of the house, this particular sequence of activities is delayed so the concrete can cure. Without the lag, work associated with stripping the forms may start as soon as the basement walls are poured. The lag delays the start of the successor activity to allow time for the concrete to cure.

Figure 17: A Lag

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Figure 18: A Negative Lag (or Lead)

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