Product and work breakdown structures

Product breakdown structure (PBS)

A PBS is a hierarchical structure of things that the project will make or outcomes that it will deliver. It helps the project team to think of what other products are needed to build the final product, and to clarify all necessary work for the creation of that final product.

Key benefits

The key benefits of using a PBS are:

  • defines the scope of the project
  • focuses the team on what is going to be produced
  • forces the team to think of the product content, eg, if it is a database, what type, how many records, what format
  • what quality criteria will be applied to the product, how will it be reviewed and what skills are required to undertake the review
  • used as a basis for creating the work breakdown structure

Creating a PBS

In order to use a PBS effectively is it recommended that you define the different types of product that your project will produce.

The first will be the management products, ie. the business case, the project plan, the risk log etc and the second will be specialist products, ie. what the project is going to produce such as a new IT system or building.

The project management framework should take care of the management products leaving you to focus on the specialist product output.

Specialist products

Products are also known as deliverables or outputs and can be recognised as they are nouns. The PBS is used to break the ultimate product, in the example below we have used a new kitchen, in to smaller and smaller components, usually about three levels.

After about three levels you start moving in to the activities involved to deliver a product, usual recognised as verbs, which form the work breakdown structure (WBS).

How to identify the products 

In all but the simplest of projects, no one person will be able to identify all of the products. The best way of identifying all products is to hold a workshop with the relevant stakeholders and project team.

Not only will this help to establish a list of products but it is an excellent opportunity to gain buy in to your project. It’s best to try to identify some of the top level product groups in advance; this might be contained in the mandate or business case. The workshop should comprise a series of steps:

  • get the group to think about the products and write each one on a sticky note
  • put all the sticky notes on the wall so they are easy to see
  • review the sticky notes and remove duplicates
  • review the remaining sticky notes and put them in related groups
  • repeat the steps, identifying any additional products, and grouping as before (three or four iterations is usually enough)

Work breakdown structure (WBS)

A WBS is a visualisation of all the tasks or activities that make up your project. It is very similar to the Product Breakdown Structure (PBS), and created in the same way, however where the PBS looks at the products (or deliverables/outputs), recognised as nouns, the WBS records the activities involved, typically verbs.

By breaking down your project into manageable chunks you will be able accurately define and organise the scope of your project. This is most commonly achieved using a hierarchical tree structure (see example below).

A WBS is also useful in that it is an easy way to assign responsibilities and resources while still being able to monitor your project as a whole. This will allow you to better estimate resources, time and risks because you can work from your smaller task up to the main project.

It is also a handy tool to show your stakeholders and make it clear what your deliverables are, and how you are going to achieve them.

Key benefits

The key benefits of the WBS are:

  • helps to further define the scope of the project
  • forces the team to think about the production process
  • forms the basis for scheduling and estimating
  • defines the work content and effort required
  • can be used as a basis for defining who needs to be involved in the project in order to deliver the required work, and assign responsibilities
  • can be used to create a cost breakdown structure to identify and manage the costs of the project

Why the need for a WBS 

  • A WBS is used to breakdown a project into easily managed components that can be effectively assigned, estimated and monitored.
  • Before you can breakdown the project you need to determine the main deliverables and milestones for a project. Once these have been established you can start decomposing the identified deliverables until you have a series of manageable tasks.

Creating a WBS

  • Ideally the WBS will be created with the project team or key stakeholders.
  • Create a product breakdown structure first as this will show the higher level products, or deliverables, of the project, allowing you to use that to break down the components further to show the work involved for delivery.
  • A brainstorming session with sticky notes is ideal.
  • Ensure that every task is independent and has a measurable aim, avoid overlap and be clear in what you want to achieve.
  • Although this is dependent on the type of project and the Project Managers personal preference, a predetermined “rule” should be used to establish the size chunks you are breaking the project into, eg. No task that will take longer than two weeks to complete.
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