What is a Work Breakdown Structure?

Work Breakdown Structure (WBS) for a book project might look like this…

Work Breakdown Structure (WBS) for a book project might look like this…

The Work Breakdown Structure (WBS) is often seen as the foundation of the project. Why is this so? This is because the Work Breakdown Structure reflects the entire scope baseline of the project, such that deliverable not incorporated into the WBS will not be part of the project.

What then is the WBS?

The WBS is a deliverable-oriented, functional decomposition of the project scope of work into hierarchically grouped work elements. The WBS shows the breakdown of work components (deliverable) into hierarchical levels resembling an organisational chart, but don’t be confused; it is NOT an organisational chart.

It serves a much different function from an organisational chart.

I usually call the WBS the backbone of the project because, from the WBS the entire scope of the project can be seen, often at a glance. The WBS reflects all included deliverable, and is used to manage the scope of the project more efficiently than a to-do list.

The WBS is prepared with the team’s buy-in. During decomposition, each level should be complete. It should include all the work of that level before decomposing further. Decomposition should be done until the lowest work unit cannot be logically sub-divided further (an/or it can be estimated with reasonable accuracy.

WBS is a deliverable-oriented decomposition and should contain only deliverable and not activities. This means that it should consist deliverable - things (nouns) and not activities or tasks (actions). In the writing project, used as an example above, we have deliverable such as “meetings, reviews, reports”. We also have deliverable such as “review completed tasks” and “Data Collection: Interview Surveys.” WBS is part of Project Scope Baseline along with Project Scope Statement and WBS Dictionary.

Work packages (the lowest levels on a WBS) are  considered decomposed at their lowest level when decomposing them offers no further value or when the work  packages can be realistically estimated and they  have a meaningful conclusion.

For a completely decomposed project, each work  package should:

  • Have a single purpose

  • Be decomposed until  it does not make sense to decompose further

  • Be estimable with a high degree of accuracy

  • Contain clearly  understood deliverable(s) or work  product(s)

Accord to Rita Mulcahy, the goal of a WBS is achieved when the work package level is reached. This occurs when the deliverable:

  • Can be realistically and confidently estimated (including the activities, duration, and costs associated with them.)

  • Can be completed quickly

  • Can be completed without interruption and without need for more information

  • Maybe outsourced

WBS is one of the most important documents on a project. It also features prominently in the Project Management exams. It should therefore should be well understood to increase success chances on the exam.