Work Breakdown Structure: The Basics & Best Practices

A work breakdown structure (WBS) is an essential project management tool that is used for planning, scheduling, control, resource management, risk management, and communications. This informative and easy-to-read article explores the basics of a work breakdown structure, and offers valuable WBS best practices for new and experienced project managers alike.

What is a Work Breakdown Structure?

A work breakdown structure is a hierarchical breakdown of all the work products that must be carried out by team members, in order for a project to achieve its various deliverables – and ultimately, to accomplish its objectives.

Key Benefits of a Work Breakdown Structure

Helps prevent work from “slipping through the cracks”.
Streamlines and simplifies schedule development.
Proactively identifies risks during the planning stage (e.g. unrealistic time estimates).
Facilitates project cost estimates and resource procurement/allocation.
Enables team members to see how their contribution impacts the overall project.
Enhances communication between the project team and external stakeholders.
Establishes a visual, standard reference that can be referred to throughout the project.

The Great WBS Project Management Debate: Top-Down or Bottom-Up?

A longstanding debate on the project management landscape is whether it is wiser to take a top-down approach when building a work breakdown structure, or if it is smarter to take a bottom-up approach. The former involves breaking larger tasks into smaller tasks. The latter involves just the opposite: identifying smaller tasks, and then using them as a foundation to identify larger tasks.

And so, which approach should project managers adopt during project planning? The answer may come as a surprise: both of them! Robust project planning should leverage both a top-down and bottom-up approach.

For example, project managers and other relevant stakeholders who are on the planning team (e.g. PMO, executives, etc.) should develop a high-level overview of a project’s primary phases and stages, break the project down into smaller sub-projects, add key deliverables, and then establish links between sub-projects and milestones.

From there, project execution-level stakeholders should add specific task planning details such as deadlines. They can also communicate with leaders when required work cannot be completed in a proposed timeline, and seek practical resolutions. For example, it may be necessary to extend a deadline, add resources, increase budget, and so on.

Clarifying Another Source of WBS (Work Breakdown Structure) Confusion

While the purpose of a WBS is to increase clarity and provide structure, there is a potential source of confusion that ensnares many new project managers (and many PMP exam takers!). In the context of a WBS, work does not refer to an activity. Rather, it refers to the work products that result from an activity. For example, the WBS for a construction project could contain “access road” (which is a work product), but not contain “pour asphalt on access road” (which is one of the activities required to complete the access road).

Generally speaking, a WBS should not include any verbs, because as discussed above every item on a WBS is a work product – not an activity. That is why the WBS item is “access road” and not “build access road.”

What is a WBS Work Package?

To understand the basics of a work breakdown structure in project management, we also need to shine the spotlight on a work package. A work package is the lowest level of a WBS, and each is associated with a unique identifier. As noted by the Project Management Institute (PMI) in its Project Management Body of Knowledge (PMBOK® Guide – Sixth Edition [2017]):

These identifiers provide a structure for hierarchical summation of costs, schedule, and resource information and form a code of accounts. Each work package is part of a control account. A control account is a management control point where scope, budget, and schedule are integrated and compared to the earned value for performance measurement. A control account has two or more work packages, though each work package is associated with a single control account.

In a sense, each control account in a WBS can be viewed as a “mini-project,” with its own associated budget, work products, resources, and milestones. Returning to our construction project example, “access road” could be one of several related work packages that are part of a larger control account called “build out”.

Work Breakdown Structure Best Practices

Ensure that the WBS includes 100% of the work that is defined by the project scope. Otherwise, deliverables will get neglected, or they will have been mistakenly assumed to be completed.
As discussed earlier, it is better to use nouns instead of verbs when developing a WBS. This helps everyone remain mindful of the fact that a WBS is not a schedule or a to-do list. Rather, it is a framework for a project.
Keep tasks exclusive and prevent them from overlapping. When possible, try not to exceed 10 (and some experts say 5) levels in a WBS.
Some project managers subscribe to the “8/80 rule,” which is that the duration of any single work package in a WBS should be at minimum of 8 hours and a maximum of 80 hours.
Try and limit each specific work package to a single reporting period (e.g. weekly, monthly, quarterly, etc.). If a work package needs more than one reporting period, then see if it is practical and feasible to decompose it further.

Using Project Management Software to Build & Manage a WBS

It is also necessary to use good project and portfolio – PPM software to build and manage a robust, reliable and functional work breakdown structure. Key must-have software features include:

Secure cloud-based access across various devices (desktop, laptop, tablet, smartphone), so that internal team members and external stakeholders can participate in the WBS development process regardless of where they are located or when they are working..
Automatic schedule status calculations that analyze a work item’s current Actual Percent Completed vs. Expected Percent Completed. This should support both hammock (work items that have sub-tasks) and leaf (work items that do not have sub-tasks).
At-a-glance work item status indicators (not active/at-risk/off-track/on-track/critical path).

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Some Final Wise Words on Building a Work Breakdown Structure in Project Management

New project managers – and indeed, some more experienced ones as well – can find themselves building a WBS that starts out simple and manageable, but quickly becomes convoluted and confusing. There is no standard tactic or technique to avoid this pitfall. However, there is some sound advice courtesy of CIO.com, “Much of project management success has to do with the fundamentals. Often these fundamentals are forgotten in our slick and sophisticated tools. Keep It Simple, Stupid (KISS) and you will often find great success!”