Work Breakdown Structure: Complete tutorial

Work breakdown structure is the discipline of breaking down and simplifying tasks such that the resulting tasks are well defined and understood.

This is done by breaking the large tasks into smaller tasks (called subtasks) and breaking the smaller tasks further into yet smaller tasks.

This process is continued until the final subtasks are small enough to be worked on and finished in just hours or days. The tasks at the end of each branch are called leaf tasks.

Traditional project management uses work breakdown structure or WBS. Most project managers are trained in WBS and PMI has been promoting work breakdown structure as the primary task management tool for years.

Wikipedia has a good page on work breakdown structure and the history behind it. You can read it here.

Work breakdown structure defines every deliverable in the project. As such, it should be the primary document in the project defining the deliverables.

The main reason for creating WBS is to come up with an accurate schedule, proper resource allocation and ability to budget the project properly.

WBS is not the schedule but the output of WBS is used to create the schedule and based on that, the resource allocation is created. Based on the above two, the cost is estimated and hence the budget of the project is determined.

Work Breakdown Structure Fundamentals

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Work Breakdown Structure Template

Regardless of the project management method you use to plan and track your projects, be it the waterfall, agile or Hybrid methods you will tremendously benefit by using the WBS to make tasks small and well understood. 

Work breakdown structure brings the right discipline to the way you manage and work on your tasks and projects.  

Let’s assume your project is to build a new house on an empty piece of land.  How do you start? 

Think high level first. What does your new house need? Let’s list all the things you need to do to have your house completed.

  1. Find an architect
  2. Find a contractor
  3. Get city permits for construction
  4. Create construction plan
  5. Estimate the cost and the budget needed to finish building the house
  6. Build the house

The above tasks in WBS are called level 1 tasks. The level 1 tasks are also called the100% rule. These tasks entirely capture what needs to be done in the project for it to get completed.

Level one tasks are parents tasks and tasks directly under them are child tasks. Child tasks could themselves be parents tasks.

Child layers clarify the deliverables of their parent’s task. A complicated project could have several layers of parent and child tasks.

Now let’s see how we can expand one of the items in the level 1 list. For this, we choose the item 6 “build the house” because building the house is more fun than chasing bureaucrats in the city hall for permits 🙂

6. Build the house (level 1 task; a parent task)

6.1 Clear the land (level 2 tasks; a child task)

6.2 Build foundation

6.3 Build walls

6.4 Build the roof

6.5 Electrical work

5.6 Water pipes and drainage

6.7 Paint the walls

Now let’s look at task 6.5 which is Electrical work.

6.5 Electrical work 

6.5.1 Layout wires (a level 3 task; a child task)

6.5.2 Add electrical Box

6.5.3 Add Sockets

6.5.4 Connect wires to sockets

6.5.5 Add light fixtures

Although we have oversimplified tasks needed in building a real house, I hope you get the idea here. First, we identified major tasks it takes in building a house. These are the level one tasks for this project.

After we did identify all major tasks (level 1 tasks), we broke each one of those tasks into smaller subtasks. Then we kept doing this process until each subtask was small enough and well understood for us to implement it easily.

Although this seems logical to break up large tasks into smaller tasks, most teams, especially those practicing Agile project management, do not follow this rule. This is a shame because WBS is one of the best tools for simplifying tasks in the project.


Dependencies in WBS

Work breakdown structure relies on dependencies to order tasks properly as they should be worked on during the project’s lifecycle.

In many cases, tasks are interrelated in complex projects, one can’t start before another task is finished.

For example, in the example above one can not start plumbing work until foundation and the walls are in place. Imagine starting plumbing work when you don’t have any walls to lay the pipes behind.

Waterfall project management method uses both WBS and dependencies. Waterfall until recently has been most widely used project management method thanks to Microsoft Project.

Using dependencies and subtasks creates a powerful tool for planning projects properly. The project plan could be oraganized in time in such a way that tasks are started when they are needed.

This means the task has everything it needs before it gets started.

The beauty of this approach is that it creates a waterfall sequence which is much easier to visualize and follow visually.


Baseline in WBS

After you finish planning a project, the resulting schedule is called baseline schedule. This is the time frame you hope will take to start and finish the project.

A project is called on time when the actual and baseline match.

Like most things in life, plans go wrong most of the time. You need to compare the actual progress of your project with its baseline.

This comparison tells you if your project is on time or late and if late by how much.

Burndown charts are a great way for tracking the progress of your project during the implementation phase.


Critical Path in WBS

The longest task path going from the start of a project to its completion is called critical path. Critical path defines how long the project will take to finish.

The duration of the critical path is the sum of durations of all tasks along the critical path.

The only way to shorten the duration of projects is by somehow reducing the time it takes to finish one or more tasks along the critical path. Doing so will shorten the critical path.

If a task which is not on the critical path gets delayed by a few days, it may or may not affect the duration of the project. But if any task on the critical path takes longer than planned, the project will be late.

During the implementation of the project, the critical path may change a few times. This happens when tasks which are not on critical take longer than planned in such way that a new path going through them is longer than the old critical path. 


WBS Dictionary

The WBS dictionary provides a detail description of each element (task) in the project. This information is referred to throughout the life of the project to find out the information about each task in the WBS. 

On Online project management software, the WBS dictionary is created from the task description for each task in the project.


Mutually Exclusive Elements in WBS

It is important that there is no overlap between what needs to be done in tasks. Otherwise, duplicate work will be done which will reduce the productivity of the team and will increase the cost of the project. 


Work breakdown structure is a fundamental tool in the war chest of any project manager. Regardless of the project management method you use, WBS can come handly making very complicated tasks broken down into simple subtask.

When selecting project management tools, make sure the application supports work breakdown structure in addition to other methods used in project management like Kanban boards, Scrum and others.


David Robins


David Robins is the founder and CEO of Binfire. David studied at both Cornell and MIT, and was the Director of Software Engineering at Polaroid for 11 years.


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