Choosing the critical path
Look again at the PERT chart below for the fence job that we worked on earlier in activity 'Durations on PERT charts'. Select the activity arrows you think are on the critical path to change them to a red highlight.
The critical path is particularly affected by delays. If wet weather means that the trench cannot be dug, then the critical path is affected and the entire job will be held up. This means that the project costs increase. Even if the brick delivery is late, depending on the float in the top sequence, it is possible that the job will still run on schedule. This is assuming that the bricks have arrived and been stacked in time for the laying stage after the foundation has cured.