Fundamentals of Project Management, Third Edition

Guidelines for Developing the WBS

One important question in constructing a WBS is “When do you stop breaking down the work?” The general guideline is that you stop when you reach a point where either you can estimate time and cost to the desired degree of accuracy or the work will take an amount of time equal to the smallest units you want to schedule. If, for instance, you want to schedule to the nearest day, you break down the work to the point where tasks take about a day to perform. If you are going to schedule to the nearest hour, then you stop when task durations are in that range.

Stop breaking down work when you reach a low enough level to do an estimate of the desired accuracy.

Remember the rule that the people who must do the work ...