The primary purpose of Work Breakdown Structure (WBS) is to aid project manager in managing project. Its concept is as simple as answer to the question, “How do you eat an elephant?” Answer: “‘One bite at a time!”. The WBS is a tool for dividing elephant into bite-size pieces.
The WBS helps project manager to organise the project requirements and decompose them into manageable work packages.
Consider a WBS as product-oriented “family tree” of project components that organises and defines the total scope of the project. Each descending level represents an increasing detailed definition of a project component. Project components may be product or services.
WBS is a fancy name for a systematic structure that show all the work that will be needed in a project.
Project Management QuickStart Guide, Chris Croft
In this article we will get familiar with the concept of WBS. We will go through simple WBS development process, understand how WBS can be integrated with the organisation and learn some of the best practices to be followed while developing a WBS.
WBS Overview
As per the PMI’s Project Management Body of Knowledge, WBS is defined as:
a deliverable oriented hierarchical decomposition of the work to be executed by the project team
There are three key words in this definition:
- Hierarchical: The WBS is usually presented in a hierarchical format, starting with the main project deliverable at the top and breaking it down into smaller components or work packages.
- Decomposition: WBS is organised in descending levels of details working from larger requirements or deliverables and breaking them down or decomposing them into smaller more manageable components.
- Deliverable: It contains every deliverable for the final product, service, or process that is being produced.
WBS represents a clear description of the project’s deliverables and scope – the what of the project. The WBS does not describe how or when deliverables will be produced.
Practice Standard for Work Breakdown Structures, Page 3, Third Edition
There are two types of WBS:
- Deliverable-Based: The deliverable based in the most common in which entire project is broken down into its component parts and smaller and smaller deliverables.
- Phase-Based: In this type, a project is organised into phases. Each phase is broken down into more specific activities to communicate what needs to be done to complete that phase. Consider an example of software development project. This project goes through defined cyclical phases. It can be broken down into Analysis, Design, Construct, Test and Roll out phases.
Deliverable-based WBS
Here is an example of deliverable based WBS for building a house. The deliverable based in the most common in which entire project is broken down into its component parts and smaller and smaller deliverables.
Image Source:Project Management QuickStart Guide, Chris Croft
Image Source:Project Management QuickStart Guide, Chris Croft
As you can observe, first level is deliverables: the main structure, the individual rooms, and the utilities or services. Below each element are the subtasks, which may further broken down to more granular levels. For e.g. kitchen is further broken down into subtasks which make up a level 3 of WBS.
Phase-based WBS
In this type, a project is organised into phases. Each phase is broken down into more specific activities to communicate what needs to be done to complete that phase.
Image Source:Project Management QuickStart Guide, Chris Croft
In the phase based WBS, the first level is focused on the various phases of the house’s construction, with more details of these phases below it.
Benefits of Work Breakdown Structure
- A Work Breakdown Structure (WBS) clarifies the project’s scope by visually outlining its requirements and final products. This shared visual representation ensures all stakeholders and team members have a consistent understanding of the project’s goals.
- WBS helps stakeholders and project teams to create bye-in in the final vision of a project.
- WBS makes communication, prioritization and collaboration among team members easier. It is also easy to share across a team and with managers in an organisation.
- By decomposing larger requirements into smaller work packages, project team is better able to estimate duration, costs and materials and identify risks.
- WBS allows 100% of the work to be included and traced back to the parent requirement. A project consists of the sum total of all the elements of the WBS. Conversely, an element that is not contained in the WBS is not a part of the project.
- Use of WBS allows to “roll up” (sum) the budget and actual costs of the smaller work packages into larger work elements so that performance can be measured by senior management team.
- WBS often starts as a team brainstorming session, around a white board or big piece of paper with everyone armed with sticky notes and markers, adding and refining and categorising all the necessary components of a project. Participating in WBS creation process can accelerate some early team building.
Structure of Work Breakdown Structure
WBS is an outline of a project with different levels of detail. The upper levels are broad categories or phases with more focused work falling into the lower level.
The WBS begins with a project as final deliverable. Major project work deliverables/systems are identified first, then sub-deliverables necessary to accomplish the larger deliverables are defined. The process is repeated until sub-deliverable detail is small enough to be manageable and where one person can be responsible.
The sub-deliverable is further divided into work packages. Work Packages are lowest level of WBS that can be estimated and managed. They produce measurable deliverables. Because the lowest sub-deliverable usually includes several work packages, the work packages are grouped by type of work – for example design and testing. These groupings within sub-deliverable are called as cost accounts.
The figure below shows the hierarchical structure of WBS:
Microsoft Project is project management tool that is widely used in the industry to prepare project schedules. You can create WBS, link tasks, assign duration and costs to the activities. You can read more about this tool here.
A simple Work Breakdown Structure development
The figure shows the simplified WBS to develop a new prototype tablet computer.
At the top of the chart (Level-1) is the project end item – The tablet prototype. The sub-deliverables levels (2-5) below level 1 represent further decomposition of work. The levels of the structure can also represent level of details of a project information. For e.g. level 1 information represents total project objective and is useful to top management; levels 2,3 and 4 are suitable for middle management; and level 5 is for first-line managers.
At level 2, there are two major deliverables – Hardware and CPU (there are likely to be other major deliverables such as software, but for illustrative purpose we are limiting our focus to just two major deliverables).
At level 3, CPU is connected to three deliverables – Power supply, Flash RAM and IO controller. The IO controller has 3 sub-deliverables t level 4 – USB slots, Internet, and Touch screen. The touchscreen has been decomposed down to level 5 and to the work package level.
Note that level 2 Hardware, skips levels 3 and 4 because final sub-deliverables can be pushed down to the lowest manageable level 5; skipping levels 3 and 4 suggests little coordination is needed and skilled team members are already familiar with the work needed to complete the level 5 sub-deliverables.
WBS levels uses numbering scheme so that tasks and sub-tasks can be associated with each other. It helps in tracing out the deliverable in large complex projects. This numbering scheme is also called as code of accounts. The code of accounts is unique number assigned to each element of WBS, so that it becomes easy to trace it back to its parent level.
The code of accounts allows product team to see sub-deliverable 1.2.3.3.4 – Resolution, maps up to Touch Screen – 1.2.3.3, then up to IO controller – 1.2.3, and up to 1.2 CPU and finally up to 1.0 Tablet Prototype.
Observe that cameras sub-deliverable includes four work packages – WP-C1, C2, C3 and C4. The Back Light, a sub-deliverable of Touch Screen, includes three work packages – WP-L1, L2 and L3
The lowest level of WBS is called as Work Package. Work Packages are short duration tasks that have definite start and stop point, consume resources, and represent cost. Each work package is a control point. A resource assigned to work package is responsible for ensuring the package is completed in time, within budget, and according to technical specifications.
A work package is basic unit used for planning, scheduling and controlling project. Work Package
- Defines the work
- Identifies time to complete the work package
- Identifies a budget to complete the work package
- Identifies resources needed to complete the work package
- Identifies monitoring points to measure the progress
WBS development is group effort. If the project is small, entire project team may be involved breaking down the projects into its components. If the project size is large, the people responsible for major deliverable are likely to meet to establish first two levels of deliverables. Further details would be rolled out in progressive manner as project gets executed.
It is always recommended to have a WBS template in place, so that it can be re-used again and again on the similar projects.
Integration of WBS to the organisation
The WBS activities are carried out by different units within organisation. The WBS is used to link the organisation units responsible for performing the work. In practice, the outcome of this is called as organisation breakdown structure (OBS).
An Organizational Breakdown Structure (OBS) is a hierarchical representation of the project organization, illustrating the relationship between project activities and the organizational units that will perform those activities.
The purpose of OBS is to identify organisational units responsible for work packages, and link those units with cost control accounts.
The integration of work package and organisational unit creates a control account that integrates work and responsibility. For e.g. at Level 5 Keyboard has three work packages that have been assigned to the Design, Quality Control Test, and Production Departments.
The intersection of WBS and OBS represents the set of work packages necessary to complete the sub-deliverable located immediately above and the organisational unit on the left responsible for accomplishing the packages at the intersection.
WBS representations
WBS can be represented in variety of different ways including graphical, textual or structural styles. The most common WBS representation styles are:
- Hierarchical WBS
- Outline WBS
- Tabular WBS
Hierarchical
One of the most common ways to represent WBS is the graphic organisational chart or hierarchical structure. In this type of structure, the child elements are connected to its parent elements by a box and an arrow.
Outline
In the outline style, each level of WBS is shown by the level of indentation and is accompanied by alphanumeric outline code.
Tabular
Another common representation of WBS is Tabular Style. Columns in a table represent the hierarchical structure in the tabular style.
WBS quality
A quality WBS is constructed in such a way it satisfies all the requirements for use in a project. A high quality WBS must meet the following charactericstics:
- Follow the 100% rule when drilling down through the levels of the WBS. The 100% rule states that every level of decomposition in the WBS must contain all of the deliverable elements, which represent 100% of its parent deliverable.
- WBS should be industry specific catering to the unique requirement of a project. It needs to be useful for your project needs
- WBS should define the entire project scope
- Captures internal, external and interim deliverables, in terms of work to be completed, including project management
- Provides graphical, textual, or tabular identification of the scope.
- Contains elements that are defined using nouns and adjectives – not verbs
- Has atleast two levels with atleast one level of decomposition
- WBS must be created by those who will perform the work
- WBS is constructed with Technical inputs from subject matter experts (SMEs) and other project stakeholders, such as financial and business managers.
- Employs a coding scheme for each element, clearly identifying its hierarchical nature when viewed in any format such as chart or outline.
- WBS can be iteratively evolved, adding more details as the project scope becomes more clearer (this is done for the complex projects)
What WBS does not contain
While the WBS is the foundation for defining the project activities needed to build the deliverables, the WBS is not the Project Schedule.
The WBS does not contain activities, tasks or milestones to be achieved and it doesn’t contain any timing dependencies for performing activities. All of this important information is part of the Project Schedule and the Project Schedule is based on the WBS.
The WBS, on the other hand, is agnostic to timing, effort, and costs.
The ABC basics of the WBS, Paul Burek, PMI Global conference 2013
Summary
A Work Breakdown Structure (WBS) is a fundamental project management tool that involves breaking down a project into smaller, more manageable components. It 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.
A Work Breakdown Structure is essential for effective project management as it ensures that all project components are included, facilitates better communication, and provides a structured framework for managing and controlling the project. By focusing on deliverables and organizing them hierarchically, project managers can ensure that all work is identified and included, leading to more accurate planning and successful project outcomes.
References
Here are the further resources if you want to go deep in this topic.
- The ABC basics of the WBS, Paul Burek, PMI Global Conference, 2013
- Practice standard for work breakdown structures – Third Edition
- Project Management: The Managerial Process, 6th Edition, McGraw Hill Education
- Project Management Quick Start Guide, Chris Croft, 2022
