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8 Must-Know Things About Work Breakdown Structure

Table of Content for Work Breakdown Structure-

  • Introduction
  • First Thing: Advantages of Work Breakdown Structure
  • Second Thing: Limitations of Work Breakdown Structure
  • Third Thing: Types of WBS- Deliverable Based and Phase-Based
  • Fourth Thing: Levels of WBS
  • Fifth Thing: Inputs for creating WBS
  • Sixth Thing: Tools & Techniques for Creating WBS
  • Seventh Thing: Approach for Creating WBS
  • Eighth Thing: Points to Remember for creating WBS- 100% Rule & WBS Dictionary

The work breakdown structure is the breakdown of the project into the deliverable activities. It is the foundation document for any project schedule. The WBS lays the foundation for all the final products such as schedule, resource planning, budgeting and monitoring plan.

PMBOK fifth edition defines the WBS as-

“The WBS is 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. The WBS organizes and defines the total scope of the project, and represents the work specified in the current approved project scope statement”.

The planned work is contained within the lowest level of WBS components, which are called work packages. A work package can be used to group the activities where work is scheduled and estimated, monitored, and controlled. In the context of the WBS, work refers to work products or deliverables that are the result of activity and not to the activity itself.

The activities of WBS are defined strictly within the scope of the project. The scope of the project is defined in the contract agreement signed between the parties. The activities are such defined that their duration and cost can be estimated easily.

The activities in the work breakdown structure are in hierarchical order. Each activity of the WBS can be allotted to a specific resource. Hence, the WBS helps in defining the control matrix for the project.

1st Thing: Advantages of Work Breakdown Structures

  1. The work breakdown structure has hierarchical activities; thus, the sequence of the work activities is defined.
  2. The interdependency of the activities can be defined in WBS.
  3. The WBS helps in more accurate estimation of duration of activities.
  4. Resource planning can be done in an effective manner by allocating the work activities to a particular resource.
  5. The project budgeting can be done by estimating the cost to be incurred for each deliverable activity.
  6. The tracking of progress and monitoring becomes easier with a well-defined work breakdown structure.
  7. The risk management plan is made on the basis of WBS.

2nd Thing: Limitations of the Work Breakdown Structure

  1. The critical path is not defined in the WBS.
  2. Details of work are not defined.
  3. The change in WBS can be very troublesome after finalising the project baseline schedule.
  4. No proper rules for defining the details to be included

3rd Thing: Types of Work Breakdown Structures

The work breakdown structures can be broadly classified into two heads- Deliverable Based and Phase-Based.

Deliverable Based

The deliverable-based WBS shows the clear relationship between the deliverables and work scope. The example of deliverable-based WBS is as follows-

Deliverable Work Breakdown Structure
Deliverable Based Work Breakdown Structure


This type of WBS divides the project into phases of the activities. The example of Phase-Based WBS is as follows-

Phase Based Work Breakdown Structure
Phase Based Work Breakdown Structure

4th Thing: Levels of Work Breakdown Structure

Levels of Work Breakdown Structure
Levels of Work Breakdown Structure

Each activity that is either decomposed into sub-activities or not constitute a level. The higher levels are called ‘Parent Level’ and lower levels are called ‘Child Level’. Each branch starting from an activity is called the ‘leg’.

5th Thing: Inputs for Creating Work Breakdown Structure

The inputs required to create a work breakdown structure as defined in PMBOK 5th Edition are as follows-

Inputs for WBS
Inputs For Work Breakdown Structure
  1. Scope Management Plan of the Project- The scope management plan specifies how to create the WBS from the detailed project scope statement and how the WBS will be maintained and approved.
  2. Project Scope Statement- The project scope statement describes the work that will be performed and the work that is excluded. It also lists and describes the specific internal or external restrictions or limitations that may affect the execution of the project.
  3. Requirements Documentation- Detailed requirements documentation is essential for understanding what needs to be produced as the result of the project and what needs to be done to deliver the project and its final products.
  4. Enterprise Environmental Factors- Industry-specific WBS standards, relevant to the nature of the project, may serve as external reference sources for creation of the WBS. For example, engineering projects may reference ISO/IEC 15288 on Systems Engineering – System Life Cycle Processes [6], to create a WBS for a new project.
  5. Organisational Process Assets- The organizational process assets that can influence the Create WBS process include, but are not limited to:
  • Policies, procedures, and templates for the WBS.
  • Project files from previous projects; and
  • Lessons learned from previous projects.

6th Thing: Tools & Techniques of Creating Work Breakdown Structure


Decomposition is a technique used for dividing and subdividing the project scope and project deliverables into smaller, more manageable parts. The work package is the work defined at the lowest level of the WBS for which cost and duration can be estimated and managed. The level of decomposition is often guided by the degree of control needed to effectively manage the project. The level of detail for work packages will vary with the size and complexity of the project.

Decomposition of the total project work into work packages generally involves the following activities:

  1. Identifying and analysing the deliverables and related work;
  2. Structuring and organizing the WBS;
  3. Decomposing the upper WBS levels into lower-level detailed components;
  4. Developing and assigning identification codes to the WBS components; and
  5. Verifying that the degree of decomposition of the deliverables is appropriate.

Expert Judgement

Expert judgment is often used to analyse the information needed to decompose the project deliverables down into smaller component parts in order to create an effective WBS. Such judgment and expertise are applied to technical details of the project’s scope and used to reconcile differences in opinion on how to best break down the overall scope of the project.

This level of expertise is provided by any group or individual with relevant training, knowledge, or experience with similar projects or business areas. Expert judgment can also come in the form of predefined templates that provide guidance on how to effectively break down common deliverables.

Such templates may be industry or discipline-specific or may come from experience gained in similar projects. The project manager, in collaboration with the project team, then determines the final decomposition of the project scope into the discrete work packages that will be used to effectively manage the work of the project.

7th Thing: Approach to Create Work Breakdown Structure

The work breakdown structure can be created by various approaches. These approaches are top-bottom approach, bottom-top approach, organisation-specific guidelines, analogy approach and mind-mapping approach.

Top-Bottom Approach

The top-bottom approach is the logical decomposition of the project work into smaller activities. The solution to a problem is identified and then it is breakdown into the achievable activities. This approach is most used and easy to follow. The divided activities can be further sub-divided into much smaller activities. Each division of activity into smaller activities is called ‘Level’.

Bottom-Top Approach

This approach is reverse to the Top-Bottom approach. In this approach, the smaller activities are combined to create the final product or service. This approach moves up the levels of WBS.

Organisation-Specific Guideline

The organisation may describe the set of guidelines and rules to follow for developing the work breakdown structures.

Analogy Approach

This approach is useful for similar projects done in the past. The work breakdown structure of previous projects can be used for the current projects by making minor adjustments as per the need of the current project.

Mind-Mapping Approach

The Project Manager or the assigned personnel can create the work breakdown structure by using his previous experience with a similar project. This approach is called Mind-Mapping Approach.

8th Thing: Points to Remember for Work Breakdown Structure

100% Rule

The sum of ‘Child’ activities should be equal to 100% of ‘Parent’ activity. This rule helps in eliminating the activities which do not contribute towards the completion of the project. Further, it also helps in identifying the missed activities.

100% Rule For WBS
100% Rule for Work Breakdown Structure

The advantage of 100% rule is that it reduces the unnecessary work. Thus, saving time and cost.

WBS Dictionary

The WBS Dictionary is to be defined for each project while making the WBS. The dictionary contains all the terms used in the WBS along with their description. The WBS dictionary typically contains WBS Code, Responsible person, deliverables, Budget, Milestones, Risks, etc.

For more on WBS, Click here.

Check your schedule quality by these techniques Click here.

For Top 20 MS Project Terms Part -1 Click here & Part-2 Click here.

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Happy Engineering!

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