What is a Work Breakdown Structure (WBS) and Why is it Important?

[a partial re-post from pmdocuments.com: http://pmdocuments/how-to-create-a-work-breakdown-structure-wbs/]

What is a Work Breakdown Structure (WBS) and Why is it Important?

According to the Project Management Body of Knowledge (PMBOK), creating a WBS is one of the Scope Management knowledge area processes that takes place during the Planning process group (See http://www.pmdocuments.com/home/pmbok-life-cycle-tutorial-and-reference/ for the table that displays the PMBOK processes mapped to knowledge area and process group.

Creating a Work Breakdown Structure (WBS) can seem simple conceptually, but there are factors to consider when applying it practically.  However, before jumping into the steps to create a WBS, it is important to understand the need for a WBS.

What is a Work Breakdown Structure?

A WBS is defined by the PMBOK as “a deliverable-oriented hierarchical decomposition of the work to be executed by the project team to accomplish the project objectives and created the required deliverables”.   A WBS does not depict time or order of execution.  All the work contained in the child elements must equal the complete work to be completed for the parent element.

A WBS can be organized are functionally, or by phase as indicated in the example below:

Phase-Based Work Breakdown Structure


A WBS contains 4 levels as indicated on the above figure.  Note that the work package is the lowest level of decomposition.  This level is considered to be a manageable component of work.  Generally, a work package should not contain less than 80 hours of work.  There is lots more information on the internet about the WBS levels 1 to 4.  We will not focus on this.  The main goal is to decompose the work to manageable componenets called work packages.

Although the above figure is a graphical example, a WBS can be developed in other formats as well.  In fact, on larger projects, Microsoft Excel or Microsoft Project are better touls for large WBS structures that contain hundreds, or thousands, of lines.

Why is a Work Breakdown Structure Important?

A WBS is one of the most critical components of a successful project because it forces the project team to carefully consider all the pieces of a project.  Specifically on large projects, it is practically impossible for one person to consider all the work necessary to complete the project.  If the project team does not take the time to decompose the work and consider all the work components, then it is safe to assume that the project team has not performed due dilegence to ensure that all the work has been identified.

On many projects, the WBS development exercise is not performed.  Rather, the project jumps into developing a project schedule.  All too often, the project seems to be progressing smoothly only to realize, later, that a key activity or dependency is missing from the project schedule because it was not considered during the schedule development.  And it was not considered during schedule development because the WBS work decomposition was not performed to try to identify all the work necessary to deliver the product or service.  Or the project schedule underestimated the level of effort for an activity, thus causing delays and potential cost overruns.  Again, the WBS exercise could help with time estimation and sequencing of activities since all the people involved in performing the work are culocated for a period of time with the one purpose of identifying all the work and providing estimates and dependencies on the work.

The WBS exercise of decomposing the work as a team is also a team-building effort.  It implicately creates a sense of agreement as well as accountability among the project team members.

Now, let’s jump into the process of developing a WBS.

[More on how to create a WBS]