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What is WBS - Work Breakdown Structure

What is WBS (Work Breakdown Structure) and how to use it

What is “Work Breakdown Structure” and what are the rules for a correct application. Here is the procedure for breaking down in details a project components

A project needs to be analyzed in all its individual phases in order to be better developed. Many complex projects involve the execution of activities that would be difficult to achieve without proper planning and organization.

The WBS (Work Breakdown Structure), also defined as “structured breakdown of the project“, results a very helpful methodology, being employed for the structuring and definition of all the activities of a project, while addressing  all the project phases in a more comprehensible way.

What is a WBS

WBS is a tool for the analytical decomposition of a project into smaller components.

The aim of the WBS tool is to organize work in more easily manageable elements  and to simply the understanding of a project, so to seamlessly communicate the project phases and activities that needs to be achieved to all the stakeholders involved.
The WBS can, generally, be applied to any type of project, including:

  • building contracting
  • construction of a building
  • organization of a construction site activities
  • design of an artifact
  • and similar

The WBS provides a valuable aid to the project manager especially in the definition and organization complex projects activities.

Therefore, the project can be hierarchically decomposed into components (for example sub-objects, activities and specific tasks) with a greater degree of detail, following a top-down approach, i.e. starting from macro-areas and then dividing them in increasingly smaller parts.

Each level always represents detailed portions of the project.

There is no defined number of levels: the decomposition depends on the complexity of the project. The decomposition ends when the last level of the hierarchy has a degree of detail such as:

  • to univocally describe the individual work to be done
  • to allow the attribution of executive responsibility

How to represent a WBS

WBS is generally rappresented graphically (tree structure) or in a descriptive way ( index structure).

In order for the WBS to bring concrete results, the goal to be reached must be clear already at a preliminary stage.
Before the work begins on each individual activity the decomposition can be progressively redefined.

WBS Diagram tree structure

Tree structure


index structure

Index structure

Work Packages in the WBS

The main objective of WBS is to identify the so-called “work packages” at the last level of the decomposition.

In the work package all the instructions to be carried out so to achieve a specific activity and task are indicated.

Work Package in a WBS

Work Package in a WBS

The decomposition to be considered optimal for each work package must:

  • be described in a clear and concise manner
  • be differentiated from other work packages
  • assign the task / activity to a single responsible person
  • univocally describe the individual work to be done

In the work package it is possible to identify:

  • all the activities and tasks to be performed
  • the necessary inputs to carry out the work and achieve the objectives
  • the description of the expected results
  • the necessary identified resources
  • the start and end dates of the works
  • the work outputs (deliverable)
  • activities that are not included in the project
  • the responsibilities of the task