The work breakdown structure in project management

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Developed by Sheren Agbarie

The work breakdown structure (WBS) were first used by the U.S. Department of Defense for the development of missile systems in the mid- 1960s. WBS was initially developed by the U.S. Department of Defense (DoD) and the National Aeronautics and Space Administration (NASA) for the purpose of planning and controlling large acquisition projects.[1] Today, WBS is a modern management technique, which may determine the success of a project in an organization. The approach of WBS allows the project team to visually see the work that is needed in order to complete a project. It is defined as being a deliverable- oriented hierarchical decomposition of the work to be executed by the project team to accomplish the project objectives and create the required deliverables. Furthermore, WBS can prove pivotal within project management planning processes by partitioning projects into stages, deliverables and work packages. If the management tool is used correctly, it can have a positive impact on other project management processes, such as activity definition, project schedule, risk analysis and response, control tools or project organization. Moreover, the WBS do not only help the project team to scope the work into deliverables but do also look into activities and tasks required to complete a project. WBS is essential since It reduces the number of surprises and furthermore, improves the ability to manage future projects in an organization.


Why is work breakdown structure important?

Project management includes identifying requirements of the project, establishing clear and achievable objectives, balancing the competing demands from the different stakeholders in the organization and ensuring that a commonality of purpose is achieved for the project. Today, many projects involve large- scale planning that effects the different departments in an organization. This is why planning is seen as being an essential part of the process. When using WBS it will become the backbone of the project of an organization. The management tool forms a consistent basis of a project by setting up deliverables, which are able to be managed, delegated and controlled by the project manager. The management tool helps the team defining the scope of the work needed in order to set up the project objectives. Furthermore, a broad execution strategy will help defining the main deliverables. To avoid losing the overview of “why are we doing this project?” the management tool helps identifying the deliverables and thereby, helping the team to organize and define the scope. Furthermore, the WBS helps the project team with the following:

  • WBS helps the project team reducing the risk of missing important tasks and work during the project period.
  • WBS helps the project team subdividing the project into smaller work packages. This helps the project team to easily manage the tasks and to have a better overview of the milestones which need identification during the project period.
  • WBS helps engaging the project team when using the management tool. This is due to that the teams are forced to each share their knowledge within their field in order to develop the WBS. Furthermore, it gives an overview of the ambiguities and uncertainty within the project and helps clarifying both incorrect and correct assumptions. WBS is a good tool when narrowing and defining the scope and furthermore, raises the important issues of the project in an early stage. The high-level of participation of the project team and the clarification when preparing the WBS helps structuring and well- define the tasks, allow the resources to be assigned to specific tasks, and furthermore, it creates accountability and commitment among the project team members.

WBS Types

When identifying the work breakdown structure there are two different types that can be set up by the project team. These are the following.

  • Deliverable- oriented work breakdown structure
  • Process- centered work breakdown structure

Deliverable- oriented work breakdown structure

The deliverable- oriented WBS is built around the project’s desired outcomes or the projects deliverables which is set up by the project team. Here, the items within the second level are the names of all vendor project deliverables that are expected to be required as part of a contract. Third level are the items which are the key activities required to establish the second level in the hierarchy. The additional levels in the structure are used depending upon the magnitude of the deliverables in which is established on the third level.

Process- centered WBS

A process- centered WBS is similar to the deliverable- oriented WBS except that it is organized, the highest level of the hierarchy of the work breakdown structure. The process- centered WBS is organized by phases in a process rather than the deliverables as the deliverable- oriented WBS. The benefits of using this type of WBS is that it encourages the inclusion of process- required deliverables, such as System Development Life Cycle (SDLC) deliverables. The process- centered WBS includes the following:

  • Level 2 activities are phases within the project. Examples of activities could be SDLC phases such as Initiation, planning, etc.
  • Level 3 are the activities required in order to complete the second level.
  • The additional levels in the hierarchy depends on the duration of the phase and the level of details required to reliably estimate the cost and the schedule of the project.

The work breakdown structure

Figure 1: An illustration of the four different areas in WBS

To get an understanding of the hierarchy of the WBS it is important to understand the main structure of the management tool. When setting up the model it is modeled after four different areas. Scope, Time, Cost and Resources. After an explanation of the main structure it is now possible to demonstrate how a work breakdown structure is conducted in a project team.

Structure of the WBS Definition Illustrations
Scope The scope is defined as the broad strategy of the project which is planned. The scope is an important step of the process when developing the WBS since it determines a list of specific projects goals, objectives, main deliverables, tasks, cost and the deadline.
Time An accurate time estimation is a skill essential for good project management. The time estimation drives the setting of the deadline for the deliverables and the planning process of the project. Furthermore, in this step a WBS dictionary is created. The WBS dictionary includes entries for each WBS component that briefly defines the scope or the statement of the work (SOW) which is a document that defines project- specific activities, deliverables and timelines. Furthermore, the SOW typically also includes detailed requirements and pricing.
Cost Cost is an essential part when planning a project. The cost within WBS involves budgeting and an integrated earned value management system (EVMS) also known as Earned value management (EVM). EVM is a project management technique for measuring the project performance and progress. EVM has the ability to combine measurements of the project management triangle which includes scope, time and costs. Furthermore, EVM is able to provide accurate forecasts of project performance problems.
Resources The last step of the WBS is identifying the resources within the project. The resources are determined by using the responsibility matrix. The responsibility matrix is used to define who in the organization is responsible for individual work elements and deliverables during the project period. The responsible matrix is divided into the following categories

R - Responsible A - Accountable C - Consult I - Inform

Figure 3: An illustration of the responsible matrix

After an explanation of the main structure it is now possible to demonstrate how a work breakdown structure is conducted in a project team.

The work breakdown structure hierarchy

The PMBOK® Guide – Fourth Edition, defines the Work Breakdown structure as “a deliverable- oriented hierarchical decomposition of the work to be executed by the project team to accomplish the project objectives and create the required deliverables”. As earlier mentioned WBS consists of Work packages which are defined in two different ways in the PMBOK® Guide – Fourth Edition. The first definition of the work package is said to be the “lowest level in the WBS, and is the point at which the cost and schedule can be reliably estimated. The level of the WBS will vary depending on the complexity of the project. It is important to know that the WBS is a repeatable process that can be used as a template for future projects.

WBS should begin in two stages. The first stage is to hold a team meeting. The teams meeting consists of that the member begins planning the first hierarchy level and furthermore, makes the project title. After this has been done the second level of the hierarchy begins. The second level in the WBS hierarchy stage contains descriptive details of all the deliverables that needs to be performed in order to complete the project and determine the timeline of the project. It is important that everything within the scope statement and the project plan is defined before starting the project. When the first and the second level is set, a decomposition and a breakdown of the deliverables of the project and its timeline can begin. The deliverables, which is attached in a tree form to the hierarchy are considered work packages. It is important that the work packages are constantly reviewed and monitored by the project manager and given a timeline upfront. The work packages are completed by different team members, which produce the deliverables which eventually fulfills the different phases in the project. The book The PMBOK® Guide – Fourth Edition suggests that a work package should not be less than eight hours but no more than eight hours.

Figure 4: An illustration of the different level in the WBS hierarchy

Example of the work breakdown structure (WBS)

In this section a definition and an exploration of the dynamics of the work breakdown structure will be conducted. As earlier mentioned the work breakdown structure is a chart or a document used to organize project work into a list of focus areas so that all work stays on track to meet the project goals.

A simplified work breakdown structure (WBS) is illustrated below with a limited number of organizing levels. When building a WBS the following points can be used.

  • Hierarchical Levels – The hierarchical level contains three levels of work.
  • Numbering the sequences – When a task has been formulated it is important to use outline numbering which has been defined as being a unique identifier for all levels when structuring the tasks. The first project level (level one) is numbered as 1.0. The second level is defined as being 1.X the X is followed by 1.1, 1.2, 1.3 etc. The different levels are defined as being the summary level. The third level is defined as being 1.X.X here the X is followed by 1.1.1, 1.1.2 etc. which illustrates the work package level. The work packages in the work breakdown structure is the lowest level in the hierarchy. Here, both cost and the schedule of the project can be reliably estimated.
  • The lowest level descriptions – The descriptions in the lowest level defines by using verbs and objects what needs to be made within the different work packages.

The following figure is an example of a work breakdown structure of a banquet.

Figure 5: An illustration of a work breakdown structure of a banquet

WBS numbering

Within the WBS every item within the hierarchy level has been assigned a unique number so the work can be identified and tracked over time. Even though the numbers have varying numbers of decomposition levels they still have a general scheme for how to number each level so that takes are uniquely numbered and correctly summarized. The following points describes the different levels.

  • Level 1: Designed by 1.0. the first level is the top level of the hierarchy of the WBS and is usually the name of the project.
  • Level 2: Designed by 1.X (e.g., 1.1, 1.2) The second level is identified as being the summary level.
  • Level 3: Designated by 1.X.X (e.g., 1.1., 1.1.2) the third level is identified as being the subcomponents to each level 2 summary element.

If the different tasks within the management tool is properly subordinated, most of the WBS will automatically number tasks using the above mentioned points.

Reflections on the use of WBS

During the analysis of the articles used for this article it has shown that there are both pros and cons when using the WBS. Even though, that the WBS is known as being the fundamental building block for most projects, there are still many conflicting viewpoints when developing and approaching the WBS. The table below shows some of the pros and cons associated with using the WBS.

Pros Cons
* WBS lays the ground work for accurate project costing. This is due to that the management tool carries out bottom-up project costing and estimating which is the most accurate estimating method. * If the scope of the project isn’t defined the WBS cannot be used.
* WBS gives an accurate project schedule which includes all tasks which is needed to complete the project in time and furthermore, meeting the delivery dates. * A poorly constructed WBS can result in a negative project outcomes including ongoing, repeated project re-plans and extensions, unclear work assignments for project participants, unmanageable, frequently changing scope, as well as budget overruns, missed deadlines and ultimately unusable new products or delivered features that do not satisfy the customer nor the objectives for which the project was initiated[2]

Work breakdown structure video

The video below is a guide for how to build a work breakdown structure. Furthermore, the video illustrates the different views on Timelines, Gantt chart, and mind map.


  1. (PMBOK Guide) Fourth Edition (2008): A Guide to the Project management body of knowledge the project management institute
    • A book regarding project management and its standard for the project management profession.
  2. Eric S. Norman, Shelly A. Brotherton, Robert T. Fired (2008): Work breakdown structures: The foundation of project Management Excellence.
    • This book is about the work break down structure (WBS) and how to use the project management tool.
  3. Sarita Harbour, StudioD (2016) Why is it important for organizations to use project management?
    • Knowledge about why an organization needs project management
  4. MSG Management study guide (2016) importance of project management for organization
    • Knowledge about why an organization needs project management
  5. Jean Scheid (2011) The importance of defining a project’s duration
    • The important of defining a projects duration.
  6. PMIS project management informed solutions (2016) Earned value management: worked example & tutorial
    • Guide about how to use EVM


  1. Eric S. Norman, Shelly A. Brotherton, Robert T. Fired (2008): Work breakdown structures: The foundation of project Management Excellence page 4.
  2. Work Breakdown Structures: The Foundation for Project Management Excellence (1) by Norman, Eric S., Brotherton, Shelly A., Fried, Robert T. Page 8
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