The Work Breakdown Structure, or WBS, is a hierarchical breakdown of a project’s work. A WBS is often created before adding tasks and breaks the project down into phases of work. Schedulers can then organize tasks into categories – such as preconstruction and construction. Essentially, the work breakdown structure is an outline used to organize project tasks. Creating a WBS helps with navigation and is often a contractual requirement for project schedules.

In Microsoft Project, you can create the WBS through summary tasks. A summary task is one that has subordinate tasks added to it. Summary tasks will act as a summary of all activities below them – giving an overview of dates, costs, and durations.

In this article, we will cover how to create a Work Breakdown Structure using summary tasks in Microsoft Project. Once created, we will also go over how to create custom WBS codes for further organization. The following examples are from Microsoft Project 2021 Professional -but the process is the same for most desktop versions of Project.

What is the Work Breakdown Structure (WBS)?

The Work Breakdown Structure is a hierarchical outline of a project’s work. It breaks the project down into discrete layers to organize tasks together. Rather than viewing all tasks under the same level, the WBS will organize them into phases of work. Not only will this assist in navigating through the schedule, it also allows you to roll up values to the WBS layer. For example, you’ll be able to see when a specific phase of tasks will start and finish and how much they will cost.

There are a variety of ways to create a WBS. For example, you can create a WBS that is process-based or deliverable-based. A process-based WBS divides the project into different phases of work – such as Preconstruction, Construction, and Project Completion. On the other hand, a deliverable-based WBS breaks the project down into different areas of scope – like deliverables and work-packages. In the following example, I’ll be creating a process-based WBS by breaking the project down into phases of work.

Before creating the WBS within MS Project, it may be a good idea to map it out within a list or a diagram. This will allow you to visualize the project and the work that needs to be completed. You’ll often see WBS’ displayed in a tree diagram. This diagram should have the project itself at the top, and break down the project’s work into different phases. You can then break these phases down further into subphases. A completed WBS diagram should look something like this:

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Creating the WBS in MS Project

In MS Project, we can create the WBS using Summary tasks. Summary tasks summarize any tasks added below them. They roll up the dates, durations, and costs for their subordinate tasks. These tasks do not drive progress – instead, they just outline the project. Summary tasks will display in bold text within the table and can be collapsed to hide their associated subordinate tasks.

When creating the WBS in MS Project, not all layers will necessarily display as summary tasks right away. Instead, some lower level WBS layers will display as normal tasks. Tasks only become Summary tasks once you add subordinate tasks to them. You do not need to worry too much about ensuring all tasks are summaries when creating the WBS. Lower level WBS layers, for example, will only become summaries once you add individual tasks to them later on.

Top Down vs. Bottom Up

There are a variety of ways to create a Work Breakdown Structure within MS Project. Two of the most common methods for creating a project outline are Top Down and Bottom Up.

The Top Down method involves working from the top of the schedule and working your way down. First, you will create tasks to represent the WBS outline. Then, you will add subordinate tasks to these layers to turn them into summary tasks. The Bottom Up method, on the other hand, involves first adding all of the individual tasks to the project and then adding the summary tasks. This allows you to organize your tasks into summaries after they’ve all been added to the project.

Both the Top Down and Bottom Up methods will allow you to create a distinct Work Breakdown Structure. In this example, I’ll be using the Top Down method. I’ll first create my summary tasks, and then fill these summaries in with the specific subordinate tasks. If you choose to use the Top Down method, it’s important to keep in mind that all the WBS layers you add will not necessarily be summary tasks from the start. Again, these tasks will turn into summary tasks once we add the individual activities to them.

Adding Summary Tasks

There are two ways to add summary tasks to a project in Microsoft Project. You can create summary tasks directly, or turn normal tasks into summaries by adding subordinate tasks below them.

To add a summary task to the project, select an empty row within the table and Insert Summary Task within the Task menu. This will add two tasks to the project: a summary task, designated in bold, and a subordinate task below it. I can now adjust the name of this summary task by selecting the Task Name cell and typing in a new name. For now, I’ll leave the subordinate task as it is and fill it in later.

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My project has three main phases: Preconstruction, Construction, and Project Completion. I already have my Preconstruction layer, so I need two more layers within the same hierarchical position. If I press Insert Summary Task again, a new summary task will be added as a subtask to the Preconstruction layer. Whenever you add a new task, summary or non-summary, it will appear as a subtask to the selected one. However, you can move tasks around in the hierarchy using the Indent Task and Outdent Task tools within the Task menu. To place this new layer in the same hierarchical position as the one above it, I can select Outdent Task. I’ll change the name of this task to Construction.

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To add another layer, I could add a new task – but I can also convert Construction’s subtask to be in the same hierarchical position. I’ll do this by selecting the subtask and pressing Outdent Task. This will cause Construction and the task below to be hierarchically equal. However, this does remove the bolded text from Construction. By changing the hierarchy, Construction is no longer a summary task. Again, you do not need to worry about this right now. Once you add additional WBS layers and tasks to this one, it will once again become a summary. I’ll change the name of the last task to Project Completion.

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Going forward, we can now break down the WBS further with sublayers. For example, during the Preconstruction phase of my project, we will be working on the Mobilization, Submittals, and Procurement. Each of these phases will have their own series of associated tasks. I can add a task underneath Preconstruction by selecting Construction and pressing Insert Task. Tasks will always be added above the one selected. I can move this task to be a subtask of Preconstruction by selecting Indent Task. Then, I’ll change the name of the task to Mobilization. I’ll continue this process until I’ve added all of the subphases to Preconstruction.

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In this same manner, I can break down each of the major WBS phases into subphases. You can add these layers as either Summary Tasks or normal tasks, and move them around using the Indent and Outdent tools. Once you have all layers added, your Work Breakdown Structure will be complete.

Another thing to note is that you do not need to adjust any details about the WBS layers beyond their name. Specifically, you should not be entering in durations or dates. WBS layers will all become summary layers later on, and summary layers will summarize the subordinate tasks below them. Although we won’t be able to see it quite yet, the durations and dates for these layers will automatically adjust to match the tasks added to them.

With our WBS complete, we now have an outline for the project. A Work Breakdown Structure without individual tasks should look something like this:

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Going forward, we can fill in these WBS layers with the individual tasks to create the project. With tasks added, the WBS layers will all become summary layers, summarizing the tasks below them. A full project with the WBS and tasks added should look something like this:

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Creating WBS Codes

With your WBS created, you can also customize the WBS codes. Work Breakdown Structure codes are alphanumeric values that show a task’s placement within the structure. These codes are not only useful for locating tasks, but also for creating reports and tracking costs.

Outline Numbers

By default, MS Project will provide you with basic outline numbers for each task. Outline numbers will designate each summary task with a specific number, and each subordinate task with a string of numbers indicating its location. These outline numbers will not display by default, but you can turn them on using columns. To add this column to the table, select the Add New Column dropdown and choose Outline Number from the menu.

We can now see the basic outline numbers for this WBS hierarchy. For example, Project Summary has an outline number of one. The subordinate layer, Project Milestones, has a number of 1.1. As the hierarchy grows farther, the outline numbers indicate the positioning of each task within the project.

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You can not edit outline numbers. However, they will change automatically when you add or move a task within the hierarchy.

Custom WBS Codes

You can go further in customizing WBS codes by defining custom codes. Custom WBS codes can be created using letters, numbers, or characters depending on your preferences. 

Before creating a custom WBS code, you should add the associated column to the table. Select the Add New Column dropdown and search for WBS. Currently, the values in this field will match the Outline Number field. The WBS field will adjust once you define a custom WBS code.

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To create a custom WBS code, select the Project menu and then WBS > Define Code. First, you can set a Project Code Prefix. This code identifies the project at the top of the WBS structure. If you are working on a consolidated master project and want to identify subprojects, this can be especially useful. You can enter in any value here – letters, numbers, or characters. This is not a mandatory field, and could be left blank.

I’ll set this to be an abbreviation of my project – COS. The Code preview window will show how the code settings will look once applied.

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Next, move down to the Code mask box. Here, you can define various values for the different levels of the WBS. You can set one Code mask for the entire WBS, or break it down by hierarchical levels. You have the option to display numbers, uppercase letters, lowercase letters, or characters within the codes. You can also adjust the character length and the code separators if needed.

I’ll set my Code mask to display Uppercase letters for Level 1, Lowercase letters for Level 2, and Numbers for Level 3. Then, press OK.

Now, we can see the customized WBS codes. The code prefix, COS, will appear at the forefront of each code. The first level of WBS layers, such as Project Summary and Preconstruction, will have an uppercase letter following the prefix. The second level of WBS layers, such as Project Milestones, will have a lowercase letter. Lastly, the third level of layers and tasks, such as Grading, will have a number. All codes will build off of the previous level’s code, with an added variable indicating its positioning.

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Renumbering WBS Codes

Any new tasks added to the project will automatically be given a WBS code. However, these codes may be out of order depending on where you add the task. I’ll add a new task underneath Preconstruction. By default, this task has a code of COS.B.d – even though it is in the position to have a code of COS.B.a.

You can choose to renumber the WBS codes at any time, which will reset them based on their positioning. To renumber the codes, select WBS > Renumber. Now, the new task has the accurate WBS code of COS.B.a.

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The Work Breakdown Structure, or WBS, is a vital part of project management. The WBS allows schedulers to break down the project into phases to organize tasks. Creating a well-defined WBS is generally a contractual requirement for project schedulers. In Microsoft Project, you can create the WBS through summary tasks. Summary tasks are ones that have subordinate tasks and summarize the work within them. Using either the top down or bottom up method, you can create summary tasks and tasks to break down the project into its various phases of work. Additionally, MS Project allows you to customize WBS Codes – which can be especially useful for tracking costs via a Cost Breakdown Structure.

With a WBS breaking down your work, it is now much easier to continue building your project in Microsoft Project.

If you have any comments, questions or suggestions, please use the comment section on the bottom of this page, and don’t forget to subscribe to our blog to get more scheduling tips & tricks directly in your inbox!

Lauren Hecker is a Microsoft Project, Primavera P6, and Oracle Primavera Cloud Instructor who teaches onsite and virtual scheduling courses. To see her next open enrollment course, please visit our calendar. To schedule an onsite or custom course, please contact us!


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