Have you heard about work breakdown structures, and wondered how they can help you in your project management efforts? A work breakdown structure (WBS) is a visual tool for defining and tracking a project deliverable and all the small components needed to create it.
This article will help you understand what a work breakdown structure is and what it is not, the advantages of using a work breakdown structure, and how to create one. You’ll also learn from the experts on how you can become confident using this powerful and essential product management tool.
What Is a Work Breakdown Structure?
The Project Management Body of Knowledge, an internationally recognized collection of processes and knowledge areas accepted as best practice for the project management profession, defines the work breakdown structure as "A hierarchical decomposition of the total scope of work to be carried out by the project team to accomplish the project objectives and create the required deliverables." With a work breakdown structure, also called a WBS, you begin with the desired outcome or product, then break it down, or decompose it, into the smaller deliverables or tasks needed to create it.
In a WBS, the deliverable can be a thing, a service, or an activity. By focusing on deliverables rather than methods—the what, not the how—a work breakdown structure helps to eliminate unnecessary work to get the intended result. A well thought out WBS aids in scheduling, estimating costs, and determining risk.
Rod Baxter, Co-Founder of Value Generation Partners, and author of the Project Management for Success Handbook calls the work breakdown structure “a necessary element to the product management lifecycle. It takes skill and practice to create, but it is essential to help you meet release dates and become efficient.”
History of WBS
In 1957, the US Navy’s Fleet Ballistic Missile (Polaris) Program was behind schedule and needed help resolving the problem. A formula was developed to determine tasks and estimate effort needed for a project based on outcome, which became known as PERT (program evaluation and review technique).
With PERT as a model, in 1962, the Department of Defence (DOD) and NASA published the first description of the work breakdown structure process. But it was in 1968 that work breakdown structure was first referred to by name. The Work Breakdown Structures for Defense Materiel Items (MIL-STD-881) established work breakdown structures as a standard across the DOD, with templates published for specific military applications, such as aircraft or ships. Even civilian contractors working with the DOD must use the appropriate work breakdown structure template.
Finally, in 1987, the Project Management Institute (PMI), through PMBOK, established work breakdown structures as standard practice for a range of non-military applications.
Advantages and Benefits of Work Breakdown Structures
Although often skipped in the planning process, a work breakdown structure is a powerful tool for finishing projects efficiently and on time. Here are some of the advantages and benefits of creating a a work breakdown structure:
- Provides a visual representation of all parts of a project.
- Offers an ongoing view for management and team members into how the entire project is progressing.
- Defines specific and measurable outcomes.
- Breaks the work into manageable chunks.
- Provides a way to make successful experiences repeatable.
- Provides a foundation for estimating costs and allocating human and other resources.
- Ensures no overlap and no gaps in responsibility or resources.
- Minimizes the chance of adding something outside the scope of work or forgetting a critical deliverable.
The Visual Advantage of Work Breakdown Structures
The work breakdown structure chart easily displays project details and status. To present your work, you have a few options. The classic WBS view is the tree structure diagram, but you can also use numbered lists or tables. An outline is one of the easiest ways to represent a work breakdown structure.
During the project, the elements in the work breakdown structure can be color-coded to indicate work status: for example, on-target=green, late=red, at-risk=yellow, completed=blue. Color coding can help you identify schedule risks at a glance.
Essential Parts of a Work Breakdown Structure
What’s included in a work breakdown structure? The following are some features created in the WBS process.
Terminal elements (aka work packages): Terminal elements, usually referred to as work packages, are the lowest parts in a WBS, beyond which a deliverable cannot be decomposed further. Work packages should be independent of other tasks, and they should not be duplicated elsewhere in the project. Another way to think of work packages is as the smallest manageable task that can be worked by an individual or team. Break the task down any further, and you run the risk of creating a to-do list and micromanaging team members.
Generally, work packages should provide work that can be completed by a team or team member within a reporting period. If your status meetings are weekly, then the work must be completed within one week. Another way to determine effort is through the 8/80 rule, which states a subtask should not take less than eight hours or more than 80 hours to complete.
WBS coding: Work breakdown structure elements are usually numbered in decimal sequence from top to bottom. For example, the 126.96.36.199 indicates that the element is on the fourth level of the hierarchy. Numbering makes it easier to identify the level of the task the element represents when referring to it out of context of the WBS chart.
WBS dictionary: The WBS dictionary describes in detail each component or task in the WBS hierarchy. It can even link to documents that further define and support the element. The WBS dictionary supports the principle of mutual exclusivity of work, in other words, no overlap, because each deliverable and sub-deliverable is so well defined that little duplication of work or responsibility is possible.
Work Breakdown Structure in Project Management
Once the project scope is available, the WBS should be the first deliverable at the start of a project. With the WBS defined, it’s then possible to scope out other resources, including human resources and particular skill sets, material resources including equipment and space, and facilities. The project scope of work and baseline schedule can be created, task lists drawn up, and assignments given.
When you manage similar projects, the work breakdown structure gets easier and can become the basis for improved delivery management. For unique projects where you and the team have no previous experience, the work breakdown structure can aid the team to define exactly what deliverables and tasks are needed for the final deliverable.
A work breakdown structure cannot be developed in isolation. Rarely can one person know everything that’s required to complete a project, least of all a project manager, who may not be a subject matter expert. Creating the WBS is a team effort.
Misconceptions About Work Breakdown Structures
A WBS does not specify how or when tasks will be done. It’s not a plan or a schedule. It is not a list of all activities, responsibilities, or an organization chart. Team leaders sometimes attempt to list all the tasks required for a project within the WBS. This could result in missed tasks causing projects to run late.
The WBS is also not just a scratch document that may or may not be used for the project. It is an important part of your project management documents. You should note any changes to the planned deliverables in the WBS, which should be subject to your company’s change control process.
Best Practices for Work Breakdown Structures
Drawing a work breakdown structure can be straightforward. But the following tips are some design principles to help you achieve the best results.
Focus on deliverables, not methods. Think about the what, not the how. The key purpose of a work breakdown structure is to define the main deliverable in terms of the small deliverables that form it. If the deliverable is not a product, then it must provide a specific and measureable outcome. For example, if you’re creating a WBS for a professional service, define the products or outcomes from that service.
When you focus on a specific deliverable, no matter at what level of the breakdown, the team or individual responsible knows exactly what is expected and what a good job looks like. You are less prone to add items that are outside of the project scope as can be the case when creating a list of tasks. When team members focus on a deliverable, rather than checking off to-do list items, they’re encouraged to use their initiative and problem-solving skills to foster innovation.
No overlap (also called mutual exclusivity). Be sure there is no overlap in scope definition among tasks in your WBS. Not only would this result in a duplication of effort, but would likely cause confusion regarding responsibility, effort, and accounting. To avoid this, create a WBS dictionary to describe each component in detail.
Follow the 100 percent rule. To eliminate work that doesn’t contribute to the deliverable, ensure that the sum of all resources in WBS, whether time, money, or anything else, add up to 100 percent. In other words, the elements in level two total 100 percent, and the level three and lower elements roll up into the level two percentage. Your finished project should never total more or less than 100 percent.
Look at the level of detail. Generally, work packages should provide work that can be completed by a team or team member within a reporting period. If status meetings are weekly, then the work must be completed within one week. Another way to determine effort is through the 8/80 rule (noted above), which says that a subtask should not take less than eight hours or more than 80 hours to complete.
Here’s another way to determine the level of detail in elements:
- If your team is less experience and needs more oversight, make work packages smaller and shorter.
- If you have a deliverable that might take longer to complete or cost more than was budgeted, again, break the project into smaller deliverables with shorter work time. With a more frequent reporting and review time, problems can be surfaced and solved sooner.
If some deliverables are not known, you can enter as much information as you know currently, and then update the document as you know more details.
Creating the Work Breakdown Structure
The first step to creating a work breakdown structure is to gather the team together. Whether your team is all onsite or virtual, it is essential for the members to participate in identifying the sub-deliverables. Rod Baxter says, “You don’t create a work breakdown structure without someone on your team who is a subject matter expert (SME). You need people on the team that really know what’s going on.” SMEs can help list all the tasks required in a WBS and identify overlapping responsibilities or gaps in the completed chart.
Dr. Larry Bennett, a Civil Engineer, Project Manager, and author of four books, sees at least two advantages when a work breakdown structure is created by the team. “There’s a potential for large amounts of input from varied viewpoints, and the ownership that results from participation.”
Your tools for capturing information can be as simple as a stack of 5x3 cards or a pad of sticky notes, that you use to write down the deliverables ard related parts, and then arrange on a whiteboard, cork board, or even a wall. For virtual teams, a similar activity can be accomplished through collaborative whiteboarding software.
To begin creating a WBS, define level one, the main deliverable of the project. Then add detail to level two as much as possible before moving to smaller chunks of work in level three, and beyond, if needed. Always try to define what’s required in the previous level in as much detail as possible before moving to the next levels.
Tools for Creating a WBS
Although you can capture your WBS with something as simple as index cards, or pen and paper, electronic templates and tools make it easier to record the chart, edit, disseminate to team members, and save with document control settings so updates are recorded through the change control process.
Templates make the job easier. Your team or company may already have a template. If not, you can create your own WBS or download one of the templates from the web and customize it. Some useful features in a template include:
- WBS coding field
- Component label field
- Company logo block
- Space for the team name
- Section for the project manager’s name
Creating a WBS in Microsoft Project
- In Microsoft Project, add the name of the main deliverable in the Task Name field.
- Add the list of sub-deliverables in the Task Name field. To indent the sub-deliverables, use the Project forward arrow key.
- Continue adding and indenting list items until you reach the work package level.
- MS Project automatically adds the WBS codes, based on the outline structure of each task/activity. However, you can create specific codes by clicking the Project tab and choose WBS from menu bar and click Define Code.
How to Gain Confidence in Creating a Project Management Work Breakdown Structure
With the sensibility required to avoid to-do lists and keep work packages manageable, measurable, and deliverable-oriented, how does a new program manager or new work breakdown structure user gain competence?
Rod Baxter says, “You just keep practicing.” According to Rod, a good project manager needs training and skill in risk management, communications management, and work breakdown structure. Competence can be gained through mentoring newbie program managers as they work their way through the ranks from such positions as project analyst, to associate program manager.
Dr. Bennett echoes this notion that practice is the key to mastering work breakdown structures.
“How does one develop confidence in any new endeavor?” he asks. “There are no magic formulae. But confidence is built through a combination of study, getting close to those who are using the method successfully, watching, asking questions, doing it oneself, soliciting feedback, learning from that feedback, and doing it again.”
Bennett says the best way to learn is probably from finding out where and how the WBS was used to create a good result. This type of information probably isn’t in scholarly publications. “Look for ‘real world’ practitioners who discuss their experience at professional meetings,” he says.
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