Chapter 7 – Scheduling Resources and Budgets

7.6. In-Depth Look: Work Breakdown Structures (WBS)

In-depth Look

In 1957, U.S Navy’s Fleet Ballistic Missile Program was running behind schedule and needed help to resolve the issue. Therefore, the team formed a Program Evaluation and Review Technique (PERT) to keep track of tasks. In 1962, the Department of Defense and NASA published the description of Work Breakdown Structure (WBS). However, it was not named until 1968. Later in 1993, WBS was introduced in corporate and other organizational projects. In June 1999, the Project Management Institute (PMI) issued a project charter to form WBS practice standards and the Planning Process Groups that begins with three essential steps:

  1. Scope Planning
  2. Scope Definition
  3. WBS development

To complete projects quickly, many organizations miss the step of forming WBS plans. If the project is delivered without proper planning and visibility, it will affect the team members and the work quality. Therefore, it is clear that WBS and planning will help the organization analyze and collect more information and predict the project’s outcome (Eby, 2021).

Work Breakdown Structure (WBS) has been defined as an “organization tree which presents a subdivision of effort required to achieve a specific objective, such as a program, project and contract” (Project Management Institute, 2008 as cited in Zecheru & Olaru, 2016 – mo matching reference for Zeheru). Likewise, Irdemoosa, Dindarloo and Sharifzadeh (2015) mentioned that WBS is efficient in project management planning. It breaks down projects into different sections, positively impacting the project schedule, risk analysis and responses, and project organization to produce a deliverable(s) successfully.

There are three (3) levels of work breakdown structure that are important to understand. According to Donato (2021), the WBS structure levels are:

  1. Level 0: project title/final product deliverables
  2. Level 1: major deliverables
  3. Level 2: breakdown of the deliverables (where possible)
  4. Level 3: deliverables that can be assigned to the team to finish

  Principles of WBS

According to Grazia Merlo (2015) a WBS offers clarity, can be broken into manageable sections and helps to monitor projects through principles that guide the design of a WBS. They include:

  1. 100% Rule

Defines the total scope of the projects and all the deliverables to reduce any gaps in the project.

  1. Mutually exclusive

Ensure there are no overlaps in the scope of the project between and among all the elements.

  1. Deliverables, Not Actions

The desired end product, service or result of the project can be predicted accurately.

  1. A reasonable level of details

A hierarchy of 2-4 levels is plenty. A practical limit of WBS granularity may be reached when it is impossible to define deliverables.

The strengths of WBS 

  1. Gives a visual representation of the projects
  2. Provides an overview to everyone in the team about the progression of the project
  3. Breaks the work into manageable chunks
  4. Best for allocating cost and time estimates
  5. Identify the risk of missing out on something in a more efficient manner
  6. Mutual exclusivity is taken into consideration to eliminate confusion
  7. Improves productivity as it will identify the skills needed to finish assignments on time
  8. Boost transparency and will make the team responsible for all tasks that have been completed or that need to be completed
  9. Each work package (lower level of WBS) is a measurable unit; therefore, it provides an exact status report of a project (Eby, 2021).

Business project managers and team members use WBS to make sure everything is well organized. Others use the WBS too. These are the creative, and technical groups that rely on WBS to track their progress. As well, event and commercial project planners, software developers, scope planning managers, and system engineers use WBS to keep them updated regarding the project’s progression (Eby, 2021).

WBS does have criticisms. Project Managers want to ensure that the work is not too detailed or extensive; it will slow down. For any changes to be made on the WBS affects the deliverables and the project’s scope. If changes are made to the deliverables, and there is no change request, this could be detrimental. Listing activities and tasks in the WBS is not advisable (Mathis, 2022). There is no limit placed on the amount of information that is required. Use of too few details does not serve the project as a tool, or too much information can become bureaucratic.

The implications of the WBS for practice are primarily positive, although, as previously discussed, it does present limitations. For Human Resources and Project Management, it serves as a planning tool to determine aspects of a project, such as roles, responsibilities, and activities that need to be completed within a specific time frame. A follow-up to assess what was achieved and what can be improved upon. A well-executed WBS can be beneficial in providing a visual representation of projects, which helps project managers visualize the project (the big picture) while also visualizing the individual pieces that work together to create a successful project. If a WBS is well-executed, it can serve Human Resources and Project Management by providing a breakdown of a project which can be personalized to the needs of each project/organization. For example, a WBS can be customized to be highly detailed or simply a general outline of the project (Luijbregts, n.d.). Overall, the WBS has the potential to be a valuable tool in project management and Human Resources practice.

WBS can be applied usefully to enhance practice in several ways. The first is to realize the project’s unique needs to determine the level of detail that the WBS should entail. As discussed previously, providing too little information or too much can negatively affect the usefulness of a WBS and could potentially be detrimental to the project. Determining the needs of your project and the level of detail required of a WBS can lead to a well-organized project and enhance the practice of Human Resources and Project Management.

If followed as precisely and accurately as possible, a WBS has the potential to keep the entire project team, including stakeholders, informed of the project and its progress (Willis, 2015). It provides a clear outline of the activities that need to be completed for the project, which gives team members clarity about what needs to be done and what outcomes are to be expected.

Another way to ensure that a WBS provides an enhanced experience is to use it in conjunction with other tools. A WBS provides an overview or breakdown of what needs to be done/accomplished. A project will require a plan/schedule, which is a Gantt chart that helps the Project Manager and team schedule the tasks and activities.

Deliverables vs. Work Packages

  • Deliverables and sub-deliverables are things such as physical objects, software code, or events. In a WBS, deliverables and sub-deliverables are represented by nouns. Work packages are assignable units of work that will be performed to create the related deliverable. A work package can be assigned to one particular project team member, one outside contractor, or another team. The work packages maybe further broken down into activities or tasks by the project team or the experts who will perform that work (see WBS dictionary later in this section).
  • Work packages are action-oriented and will be represented by phrases containing verbs. The cost of a deliverable is the sum of all of its related sub-deliverables. As well, a work package is somewhat similar to specific tasks that need to be completed and can be delegated to the appropriate person.

Since the WBS provides a natural way to summarize (or “rollup”) the costs and labour involved for various sub-deliverables, it also provides the project team with the information need to determine whether some deliverables would be better performed by an outside specialist who could deliver the item or service more cost-effectively.

WBS Numbering

Project managers use the WBS during project execution to track the status of deliverables and work packages. The items in a WBS are numbered so it is easy to understand the deliverable, or sub-deliverable, to which any particular work package is related.

This numbering system allows for easy reference and filtering. For example, an electrician working on the Warehouse project only needs to receive details and updates that are related to work packages that start with 2.2 (the Electrical sub-deliverable). This would be the same number that the Accounting Department would use for billing.


Decomposition is the process used to break the project scope of work into the deliverables, sub-deliverables, and work packages involved in completing the project.

The process of decomposition begins with identifying the highest-level deliverables. These deliverables are then broken into sub-deliverables. Many layers of sub-deliverables may be needed for a project. A general rule of thumb is that if the WBS has more than 5 layers of sub-deliverables, the project team should reassess and try to simplify the WBS structure (often by changing the way higher-level deliverables are grouped and broken down).

Once the lowest level of deliverables has been reached, the next step is to break the sub-deliverables into work packages. The work packages describe the work that needs to be done to create the sub-deliverable. Remember that work packages typically contain verbs and can be assigned to a person, team or contractor.

Once the project team has drafted the WBS, they should ask themselves: “If all the work packages were completed, and all the deliverables in this WBS were delivered, would the project be complete?” If the answer is no, then pieces of the WBS are still missing. If the answer is yes, then the project team can move on to creating the WBS dictionary, getting bottom-up estimates on time and resource requirements, and planning how to schedule the work.

The WBS Dictionary

The WBS dictionary (also referred to as an activity list) provides detailed documentation about each work package, including;

  • Who is responsible for completing the work package?
  • What resources will be needed to complete the work package?
  • What deliverable(s) is the work package contributing to?
  • What deadlines or milestones are associated with this work package?
  • What are the acceptance criteria for this work package?

When the WBS is created, not all of the information about the work packages is known (for example, the estimates for labour and material costs). Remember from Chapter One that the planning process continues throughout the execution of the project. As a result, the WBS dictionary is a “living document” that will be augmented, edited and updated as the project moves forward. Figure 7-3 is an example of a WBS Dictionary entry; note that several items will be added later in the planning process. The dictionary in Figure 7-3 includes the following columns: item number, description, constraints, responsibility, milestone, schedule, resources, cost, quality, acceptance criteria, references and guidelines.

An example of a WSB Dictionary entry
Figure 7-3: WBS Dictionary entry example.(Click to enlarge)

Class of 2022 Contribution: Adenike Afolabi, Hanin Al-JjowJ, Sabinne Serban, Kanica Arora

Sections: Deliverables vs. Work Packages, WBS numbering and Decomposition adapted from: Project Management Fundamentals by Great River Learning is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.