Cost estimating, Cost Control and Planning have not the same needs in terms of levels of details. But all these disciplines of the Project Management must be based on the same WBS. This is the paradox apparently…
Cost Breakdown Structure (CBS) is the consolidation of the costs on the axis of the 3D WBS, I mean on the different floors of the Zones, Products and Activities tree structures.
The picture below shows that the tree structure of the Cost estimating has a strong level of details for Products (level #5). It is Product oriented because we estimate the cost of something (What? = Product). The level of detail for the schedule is strong in terms of Activities (level #5) because the schedule shows how we do the works (How? = Activity or action). It is not the same needs.
Because all the tree structure of the 3D WBS are linked together, Costs and schedule data can be consolidated throughout the tree structures. The picture below shows that there is an optimal level of Project Management to produce reporting and dashboards common to the Costs and the Schedule.
