WBS - Work Breakdown Structure

Author: Manuela Vazquez, s222648

Abstract

The International Organization for Standardization (ISO) defines the Work Breakdown Structure (WBS) as a “decomposition of the defined scope of a project or programme into progressively lower levels consisting of elements of work” . It represents all the deliverables to be produced by the project or program for which work activities will be defined, planned, and executed . No matter whether the project solution will result in a physical product, service, or process, all can be defined from the deliverables’ perspective. Therefore, the WBS is a key component in the project planning process, regardless of industry or discipline. Failing to do an appropriate WBS can result in rework, schedule changes, poorly distributed resources, and budget increases .

The present article first summarizes the different definitions of the WBS and references the current standards which directly address it. The history of its origin and development are also presented. In addition, the key attributes of the WBS are described, as well as the aspects that need to be considered when creating and evaluating the tool. The different possible visualizations for the WBS are presented, along with an extensive example of its application. Furthermore, the limitations of the WBS will be explored, as well as other complementary and related tools, such as the Organizational Breakdown Structures (OBS). Finally, additional bibliography is recommended for readers who want to learn more about the topic.

Definition and use

The WBS is a hierarchical decomposition in which the project or programme scope is divided into successively smaller work breakdown structure elements to be carried out by the project team . ISO 21511 standard provides guidance on the use of this tool for those involved in developing and using it, and complements ISO 21500 and ISO 21504.

• ISO 21511:2018 Work breakdown structures for project and programme management
• ISO 21500:2021 Project, programme and portfolio management — Context and concepts
• ISO 21504:2022 Project, programme and portfolio management — Guidance on portfolio management

In addition, the Project Management Institute (PMI) released the third edition of the "Practice Standard for Work Breakdown Structures" in 2019. As explained by the PMI, "this practice standard aligns with other recent PMI standards, including A Guide to the Project Management Body of Knowledge (PMBOK® Guide) – Sixth Edition, providing practitioners with an indispensible tool to consistently track schedule, budget, risk and performance, regardless of discipline" .

History

Origin and development of the tool, retrieved from “Getting Started with Work Breakdown Structures (WBS)”.

Key attributes

• It is “deliverable orientated”.
• It is hierarchical
• The 100% Rule (Haugan, 2002, p 17)
• Develop them down to a level of detail using the 8 to 80 rule
• Can be represented in a variety of ways

How to create a WBS

Even though there is no single "correct way" to prepare a WBS, some generally recommended guidelines can be followed by the project team to ensure that proper WBS characteristics exist for any project. Considering the following general guidelines will assist in creating and implementing the WBS:

1. The WBS is prepared as early as the project definition will permit .
2. A preliminary WBS is initially developed early in project formulation to define the top levels of a WBS. These preliminary elements should reflect the entire scope of the project including project definition, development, launch, and operations .
3. A brainstorming session should be organized with the various departments involved in the project, inviting all relevant stakeholders. Furthermore, involvement in planning leads to motivation to carry out the plan . All relevant stakeholders need to be involved to ensure that proper planning is done and that all parties agree on the final WBS prior to approval..
4. In this aforementioned session, first identify the main goal of the project, then the deliverables, and lastly the activities required for each deliverable. Focus primarily on one higher level element at a time, this way the ability to think about the lower-level elements required is enhanced and omissions are avoided .
5. Changes in the project are usually inevitable as learning happens during the life cycle of the project. Therefore, “consideration should be given in developing the WBS as to how changed requirements and work content will be incorporated into the approved WBS” . Hence, change control is crucial. As the project scope of work changes, the WBS is revised to reflect formally approved changes. Again, all parties involved must agree on the changes.
6. All top-level WBS elements do not have to be subdivided to the same level of detail. As associated element risk, cost, or complexity increases, further breakdown may be necessary . It is an iterative process: to go up the structure “why?” should be asked, and “how?” when going down, until the WBS is ‘stable’ and no major changes are required.
7. To ensure accurate and good communication between the people involved, the definition of the terms used should be consistent over the entire WBS and, ideally, across all projects carried out in the same organization .

Related Tools

• Functional breakdown
• Organizational breakdown structures (OBS)
• Risk breakdown structure (RBS)
• Product breakdown structure (PBS)

Annotated bibliography

Good resources on WBS include:

• “The ABC Basics of the WBS” by Paul Burek, 2013
• “The Intelligent Structure of Work Breakdowns Is a Precursor to Effective Project Management”, Homer & Gunn, 1995
• “Practice Standard for Work Breakdown Structures”, Third Edition, 2019
• ISO 21511:2018, "Work breakdown structures for project and programme management"
• ISO 21502:2020, "Project, programme and portfolio management — Guidance on project management"