About lead and lag time in scheduling

With each dependency, you can assign lead time or lag time. Lead or lag allows you to further adjust the starting date of a task in relation to its predecessor.

Lag time

Lag provides a delay between tasks. For example, in the Predecessor window for the task Stripping Forms, you assign the task Pouring the Foundation as its predecessor. Because you cannot strip the forms until the concrete is poured, click 1-Start/Finish in the Relation list. However, the forms cannot be removed until the concrete has cured, so enter 3 in the Lead/Lag text box. When looking at the schedule, the Stripping Forms task cannot start until three days after the completion of Pouring the Foundation. Therefore, you enter lag as a positive value.

Lead time

Lead provides an overlap between tasks. For example, in the Predecessor window for the task Electrical, you assign the task Roofing as its predecessor and enter 1-Start/Finish in the Relation column. An electrician can begin wiring the building a couple of days before the roofing task is completed since the structure is now partially covered by roofing. In the Lag/Lead column, enter -2. When looking at the schedule, the Electrical task can begin two days before the finish of the Roofing task. Therefore, you enter lead as a negative value.