Monday, March 04, 2024

WBS Level – 0 (L0) Vs. Level – 1 (L1) with Oracle Primavera P6 and Microsoft Project


Many times, while interacting with the project management or agile practitioners, questions come on the levels of the work breakdown structure (WBS). In particular, the biggest confusion is about the differences between Level 0 (L0) and Level 1 (L1). 

Most project management literature and tools are focused on L1 of the WBS and rarely mention L0! This results in questions such as:

  • Is L0 possible in a WBS?
  • What does it represent?
  • How is it managed with a software tool?

In this article, I’m going to explore the answers to the above questions with hands-on practical software tools. First, to understand, let’s briefly discuss various levels of WBS.

Various Levels in WBS

Following are the levels of WBS:

WBS Level – 1: This is the highest level in a WBS and it represents the entire scope of work to deliver the product or service.

Considering an example of TESTPROJECT (name of the project), it can be assigned a numerical number 1 or a WBS code TESTPROJ. We will see them with examples shortly.

WBS Level – 2: This is the first level of decomposition. These are the major deliverables or areas of work. Remember, a WBS is a deliverable-oriented hierarchical decomposition of work. It means the WBS is broken-down/decomposed the way you want to deliver your work. 

Considering our previous example, the numbering at L2 will be:

  • 1.1, 1.2, 1.3, 1.4, … 1.n

WBS Level – 3: It’s the next level of decomposition or decomposition of L2. Here one can have the major deliverables/areas of work broken down further for better estimation and understanding.  

The numbering schemes here can be:

  • 1.1.1, 1.2.1, 1.3.1, 1.4.1, … 1.n.1
    • At the level of 1.1.1, you can have 1.1.2, 1.1.3, 1.1.4 …
  • Using TESTPROJ code, it’ll be TESTPROJ.1.1, TESTPROJ.2.1, TESTPROJ.3.1, TESTPROJ.4.1, … TESTPROJ.n.1
    • At the level of TESTPROJ.1.1, you can have TESTPROJ.1.2, TESTPROJ.1.3, TESTPROJ.1.4 …

What is Level – 0 (L0)?

This is where the confusion comes-up! Why does one need Lo?

To simplify, here are certain key points with respect to L0:

  • If present, it’s the highest level of the WBS tree or tabular structure.
  • Below L0, in the WBS, you will have L1.
  • L0 is NOT used in the numbering schemes, rather L1 is taken-up for it.
  • L0 is useful, when you are managing multiple projects together in a single file. For example, one can have a large project with multiple WBS (each starting with L1). 
  • Looking at the previous point, all smaller projects, under a large project, can have their own numbering schemes. 

Now, let’s see the practical usages of it.  

L0 and L1 - Oracle Primavera P6

Primavera allows up-to 20 WBS levels by default. You can check the levels under the Admin menu > Admin Preferences > Data Limits tab. I’ve changed it to four for this article.

Next, I added four levels in the WBS tab of Primavera P6’s main screen. 

As shown above:

  • TESTPROJ = Level – 1
  • TESTPROJ.1 = Level – 2
  • TESTPROJ.1.1 = Level – 3
  • TESTPROJ.1.1.1 = Level – 4

So, the highest level is Level 1 in Primavera P6. 

Next, I’ll modify this WBS to make it more formal and have a couple of work packages. 

As you can see, now we have two work packages: Work Package 1 and Work Package 2 at L2. The WBS codes are WP1 and WP2, respectively. The Project ID is another column as TESTPROJ, which is L1. 

Did you notice how the WBS code is noted? It’s ProjectCode.WBSCode, e.g., TESTPROJ.WP1.

Next, for each work package, we have four activities and they are all linked with finish-to-start (FS) dependencies. This is shown in the Activities tab. I’ve added the WBS, WBS Name columns under the Activities tab to have better clarity.

As one can check, there is a Work Package 1 (WBS Name) that has a WBS (Code) as TESTPROJ.WP1. It has four tasks: Task 1-1, Task 1-2, Task 1-3, and Task 1-4. All the tasks in the respective packages are linked.

Considering the WBS levels, we can have following interpretations:

  • Highest level is TESTPROJ (L1).
  • Next level is TESTPROJ.WP1 (L2) and TESTPROJ.WP2 (at Level 2).
  • These are also reflected in the graphical side of the Gantt Chart.

Hence, in Primavera P6, there is no Level 0 (L0), but only Level 1 (L1). This L1 can be further decomposed to any level you want.

L0 and L1 - Microsoft Project 

To demonstrate Level 0 (L0), I’m going to use the MS Project software. The below commands/usage will be valid for all versions of MS Project from MS Project 2003. 

Just like the previous situation, here too, we have a Test Project (Project Name) with two work packages – Work Package 1 and Work Package 2. Each work package has four activities. The plan is shown below. 

Unlike Primavera P6, there is no separate WBS tab or command available in MS Project. To see the WBS code, you have to add the “WBS” field available in the software. This can be added by right clicking and using the command “Insert Column”. 

When added, we will get the following view.

As shown above, in the Test Project we have two work packages (WP 1 and WP 2).

  • Test Project = L1
  • Work Package 1 and Work Package 2 = L2
  • Various tasks under the work packages = L3

So, where is L0?

For that, you have to enable the Project Summary Task command under Format tab > Show/Hide group. 

After you enable it, Level 0 (L0) will appear in the MS Project plan as shown below.

As shown:

  • A new line entry is auto-added and it’s named Project 1This is Level 0 or Lo.
  • This is one level up the L1 and also shown in the graphical side of the Gantt Chart.
  • The lower levels such as L2 (work packages) and L3 (tasks) are also shown.


In conclusion, you can say Primavera P6 does not have L0, but MS Project does! Earlier in the article, I’ve noted certain key points about L0 for a WBS.

Another usage of L0 is when in the same project, you have different kinds of work and you want to keep them all at L1. Say, a project has different work and you want to have different WBS codes being applied to those work. With L0 availability in MS Project, you can perform those operations.

However, if you are using Primavera P6, there is no L0 and it’s not needed. This is because in Primavera, the WBS code is built separately in another tab and then activities are added to the WBS levels. 

I hope this article gives clarity on how and when the L0 and L1 are used in a work breakdown structure with real-world and widely used software tools.


[1] Online Course: MS Project – Live Lessons, by Satya Narayan Dash.

[2] Article - Work Breakdown Structure in Traditional and Agile Life Cycles, by Satya Narayan Dash

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