WBS (Work Breakdown Structures) - A Step By Step Guide

Abstract

The WBS provides a framework for planning, controlling, executing, and managing the project's work. Furthermore, it converts the uncertain challenge into smaller components called tasks that can be easily assessed, measured, managed, and communicated. WBS components play an essential role in project management, planning, and control, defining relationships between scope, time, and cost. This article provides some of the most popular definitions to work breakdown structures in the first chapter. Followed by a step-by-step guide to work breakdown structures. This guide is meant to provide new project managers with all the knowledge necessary to get started with creating a work breakdown structure for their own projects. Covered topics in chapter three include work plan templates, activity definitions, constructing work breakdown structures, task dependencies, resource planning and acquisition, team development, cost estimating and budgeting. Lastly, in chapter four, some of the most important best practices for creating work breakdown structures are described.

Definitions

As a starting point, the Project Management Institute defines work breakdown structures in its The standard for project management and a guide to the project management body of knowledge (PMBOK guide) Seventh Edition as follows:

• "Work Breakdown Structure (WBS). 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 following is the definition of work breakdown structures of the NASA Work Breakdown Structure (WBS) Handbook:

• "A WBS is a product-oriented family tree that identifies the hardware, software, services, and all other deliverables required to achieve an end project objective. The purpose of a WBS is to subdivide the project’s work content into manageable segments to facilitate planning and control of cost, schedule, and technical content. A WBS is developed early in the project development cycle ... Work scope not contained in the project WBS should not be considered part of the project. The WBS divides the work content into manageable elements, with increasing levels of detail."

Small changes in the definition of WBS over the decades can be observed when taking a look at Gregory T. Haugan's definition in "Effective Work Breakdown Structures" from 2002:

• "The WBS is an outline of the work; it is not the work itself. The work is the sum of many activities that make up the project. A WBS may start either as an informal list of activities or in a very structured way, depending on the projects and the constraints, and it can end wherever the planner wants it to. The goal is to have a useful framework to help define and organize the work and then to get started doing it."

A Step-by-Step Guide

The following guide is meant to help project managers to go from zero to 1 in developing a work breakdown structure for their own project. It is also meant to be mainly for beginners to get started with the concept and provides easy-to-follow instructions for each step. Developing a work breakdown structure is an important part of project planning and the official name of structuring the work of a project in an outline and going from phases on the highest level to tasks on the lowest level.

Project Work Plan

The first step in developing work breakdown structures is to create a project work plan. At the beginning of the project work plan, it is recommended to brainstorm and answer the following questions:

• What is the primary goal?
• Which intermediate deliverables need to be met to achieve the primary goal?
• How will the project be organized in regard to remote teams or collaborating groups?
• Which detailed tasks are needed for the intermediate deliverables to be achieved?
• What is the needed order of the tasks or is a specific sequence required?
• How much time do specific tasks take and what determines the effort?
• Which skills are required to fulfill a task?
• Who will do which task and when?

Furthermore, the project definition document can be used as a starting point for the project work plan. All the things the project needs to deliver should be investigated and a way of tracking the progress chosen. The chosen template needs to be reassessed if it fits the specifications of the project. Additionally, the summary schedule needs to be checked for completeness, and the budget for accuracy. To create a plan, the project manager has to know what the project is supposed to deliver. This information can be found in the definition document made during the idea phase.

Work Plan Templates

Work plan templates can be effective shortcuts to getting started with the work plan. Many projects, especially in the same field, have a lot of similarities, it can be useful and timesaving to use a template. However, since these templates include hundreds of predefined tasks, it is important to go through them thoroughly and exclude the unfitting ones, and add potential missing tasks.‎
If there are no suitable templates available or it is the first work plan of its kind, it needs to be created from scratch. The following paragraphs will focus on this case.

Activity Definitions

If the Work Plan needs to be developed from scratch, the project manager should start by defining the main activities. Defining activities means figuring out and writing down the specific tasks needed to create deliverables and tasks listed in the definition document. Ideally, the project manager will work with the project team during this step, however, sometimes the team is not chosen until after this step.

To start defining activities, the project manager should think about four main things:

1. Definition document – The project's reasons and goals in the scope statement are important for this process.‎
2. Past projects – What was needed in similar projects before can help us understand what's needed in this one.‎
3. Limits – Things that restrict the team's choices, like a set end date or a strict budget, need to be taken into account.‎
4. Basic work breakdown structure – A simple breakdown of the project into phases can help guide this step.‎

Constructing Work Breakdown Structures

At the beginning of creating a Work Breakdown Structure, tasks should be grouped by similar traits. These groupings can be structured by different similarities such as activities, geographies, or functions. As described earlier, using an existing template can greatly speed up the process of defining activities. However, if no such template is available, the clustering of tasks "can be as much art as science". After the grouping process, the level of detail of the tasks should get assessed. Too little detail would be a three-phase plan with 1000 hours each and the other end of the spectrum, for example, a plan with 3000 one-hour tasks would be too detailed. One rule that can help with figuring out the amount of detail is the so-called "Rule of 80". “The 80-hour rule stipulates that you break a project into tasks of 80 hours or less, each of which must result in a tangible product or deliverable.” In general, the level of detail for a project varies for different projects and needs to be decided each time. However, rules of thumb such as the "Rule of 80" and experience can help a lot.

How to deal with "Non-Deliverables" Tasks
When going through the tasks of the work breakdown structure, one might think that many tasks are missing which are not deliverables themselves but are helping or are needed for other deliverables. These types of tasks are called "scaffolding tasks". They are named after the scaffolding in the construction industry. Similarly, as scaffolding is only used during the construction process of a building, and then removed these tasks are only done during deliverables. They can take up significant time and recourses and therefore need to be considered in the planning process.
Three main categories of scaffolding tasks are being distinguished:
1. Support Tasks - An example of a support task would be writing a script to convert a database from one format into another one. The deliverable is the database in the new format and the support task is writing the script for the conversion.
2. Project Management Tasks - This type includes tasks such as task tracking, analysis, and scope management.
3. Administrative Tasks - This category includes tasks such as printing, non-project meetings, and more.

Relationships of Tasks in the WBS

Task Dependencies

The next step, after building the work breakdown structure and deciding on tasks, is to analyze the tasks in regard to dependencies between each other. This step is highly important because some tasks can only start when others are done. An example would be that the foundation of a building needs to be completely finished before the building of walls can be started. Therefore, the predecessor and successor relationships of tasks need to be examined thoroughly. This also enables the creation of the critical path of the project.
Four kinds of task dependencies are distinguished:
1. Finish-to-Start - If two tasks have a finish-to-start dependency, the predecessor task needs to be completely finished, before the successor task starts immediately when the first one is done.
2. Start-to-Start - If two tasks have a start-to-start dependency, the predecessor task needs to start, before the successor task starts.
3. Finish-to-Finish - If two tasks have a finish-to-finish dependency, the successor task can not be finished, before the predecessor task is done.
4. Start-to-Finish - If two tasks have a start-to-finish dependency, the successor task is not allowed to finish, before the predecessor task starts.

The Critical Path

Gus Cicala defines the critical path as "the longest path through the network, based on task duration, which dictates the shortest amount of time the project can be completed." Therefore, calculating the critical path becomes crucial to identify the minimum time it takes to finish the project. The critical path is calculated by calculating the overall time of every possible path in the project and finding the longest one. Following this calculation, the slack can get calculated. The slack is the maximum time delay all noncritical paths are allowed to have before the whole project is delayed.

Resource Planning and Acquisition

Resource Planning

As defined by the Project Management Institute in the PMBOK guide, resource planning is the process of managing what resources, such as people, equipment, and material are used for which specific activity and what amount is consumed. This process is highly connected with cost estimation and is furthermore affected by organizational planning and communication planning.
The results of this process can be summarized in the following three categories:
1. Role and Responsibility Assignments - Roles and responsibilities can be easily identified by the two following questions "Who does what?" and "Who decides what?". These need to be assigned to the correct stakeholders, normally people actively working on the project. This usually concerns the project managers and individual contributors.
2. Staffing Management Plan - The staffing management plan is included in the overall project plan and regulates the onboarding and offboarding of human resources to the project team. This plan can vary a lot in regard to formality and level of detail, depending on the different needs of the individual project.
3. Organization Chart - The organization chart is a visualization of the project reporting relationships and is also highly customizable depending on the project.

Staff Acquisition

Another important step in the project is the staff acquisition. This process includes assigning required human recourses to the project. Usually, the project manager has to negotiate for the desired human recourses. If the required staff is not available in-house, the project manager is required to procure the necessary staff specifically for the project. The following steps help the project management team ensure a smooth staff acquisition process:
1. Staffing management plan - The staffing management plan encompasses the staff requirements.
2. Staffing pool description - If possible, the project management team needs to take certain characteristics of recruited staff into consideration. This includes previous work experience, personal interests, personal characteristics, and availability.
3. Recruitment practices - The acquisition process can sometimes be further constrained by the recruitment practices of involved organizations.

Team Development

Following resource planning and acquisition, the next step is team development as defined by the PMBOK Guide. During the team development process teams follow similar patterns and phases in the beginning. This is necessary to ensure long-term success and development into a high-performing team. It is necessary for the project manager to know which phase the team is going through to support this process properly. One of the team development models is the Tuckman Ladder. Tuckman defined four different stages every team is going through. These include forming, storming, norming, and performing.
1. Forming - The group working on the project meets for the first time. They introduce themselves and share important information about their role, what they're good at, and other things that are helpful to know. This usually happens at the start of the project in a meeting.
2. Storming - When a project team starts to work together, some members might try to show that they are more important than others. During this time, people's personalities, strengths, and weaknesses become present. Sometimes, people might have disagreements or difficulties working together. This is called storming and it can take a while or be over quickly.
3. Norming - During the norming stage, the project team begins to work together as a group. Everyone knows their role in the team and how they work with the other members. They might face some problems while working, but they are quickly resolved, and the team starts to take action to complete the project.
4. Performing - When a project team has been working together for a while, they become very good at what they do. This is called the mature project team stage. They can work together very well and achieve more than they could individually.

To ensure a fast and efficient team-building process, the project manager can fall back on team-building tools and exercises. Some of these are listed below:

• Team building activities - These activities are meant to improve the performance of the team by making the members more comfortable with each other. The range of activities can vary from a short five-minute exercise to a multi-day seminar packed with activities.
  
• Reward and recognition systems - Reward and recognition systems are formal management actions that encourage wanted behavior. These systems must make the connection between outcomes and reward clear, explicit, and reachable to be effective. Project-specific reward and recognition systems should also be developed, taking cultural differences into account, to ensure that they are appropriate and effective.
  
• Collocation - This is the concept of bringing the project team physically together. Working in the same room, for example, encourages communication between team members.
  
• Training - Training summarises all activities with the goal of improving skills, knowledge, and capabilities. Training distinguishes into two types called formal (classroom, computer-based) and informal (peer feedback) training.
  

Cost Estimating and Budgeting

Cost Estimating

Cost estimating includes the process of trying to calculate how much it costs to produce the desired deliverables of the project. This is different from pricing which is more of a business decision. Two resources are used to calculate the cost estimation. Firstly the work breakdown structure is used to organize the cost estimates. Secondly, the unit rates are required from resources such as the staff and raw materials.
In general, two commonly known approaches are used for cost estimation:

• Top-down estimating - When top-down estimating is chosen, project managers fall back to cost data from previous, similar projects to predict costs. This is especially helpful in projects where little data is available or in the early stages of projects.
  
• Bottom-up estimating - If no previous data is available or projects have a lot of uncertainty, bottom-up estimating is used. Hereby, project managers divide tasks into individual work items for which it is easier to estimate the cost. Afterward, the overall cost for the project is calculated by adding the cost of all the individual work items.
  

Budgeting

Cost Budgeting is when each individual task is connected to the overall cost of a project to measure if the project is on track in regard to cost. This process requires the cost estimate, the work breakdown structure, and the project schedule. This results in the so-called cost baseline, which is a plan for how much money will be spent during each phase of the project. The cost baseline is usually visually presented in an S-curve and helps the project manager to keep track of how much money was spent and if the project is still on track.

Best Practices

Deliverable Oriented

The WBS (Work Breakdown Structure) is focused on the end result or what needs to be delivered. A deliverable is something that must be made to finish a project and it can be a product, result, or service. The WBS is aligned with deliverables, meaning it is focused on what needs to be delivered.

Hierarchical Decomposition of the Work

Another key concept of WBS is the hierarchical decomposition of work which breaks down the project into smaller parts so that it's easier to manage. This process is called "decomposition". The WBS makes it clear what the project involves by dividing it into smaller parts that are easier to understand. The number of levels used in the WBS should be enough to make sure the project can be managed well.

The 100% Rule

The 100% Rule is an important part of the WBS (Work Breakdown Structure). This rule says that the WBS must include all the work for the project, including project management, and must add up to 100%. This means that the WBS should only include the work that is part of the project and should not include any extra work. The 100% Rule applies to all levels of the WBS and the work for each level should equal 100%.

Annotated Bibliography

Project Management Institute, The standard for project management and a guide to the project management body of knowledge (PMBOK guide) Seventh Edition, (Project Management Institute, 2021)
As one of the most widely recognized standards in the field of project management, this reference is the perfect starting point for most concepts in project management. It provides many definitions including one for work breakdown structures. To help with planning and controlling the costs of the project, this reference suggests developing the work breakdown structure early in the project stages. It also includes guidance on the chosen level of detail of WBS, aligning WBS with the project scope and objectives.

NASA, NASA Work Breakdown Structure (WBS) Handbook, (National Aeronautics and Space Administration, 2018)
With NASA being one of the organizations with the most famous projects in history, using their own handbook for work breakdown structures helps to understand their approach better and gives a different view on the concepts of WBS. Within this article, this source provided another definition for WBS. Furthermore, the handbook includes examples of WBS from NASA projects, which can serve as a reference for project managers who are developing WBS for their own projects.

G. Cicala, The Project Managers Guide to Microsoft Project 2019 Covers Standard, Professional, Server, Project Web App, and Office 365 Versions, (Apress, 2020)
With the main focus of this article being to provide a step-by-step guide on how to create a work breakdown structure for new project managers, this literature fits perfectly. Even though it describes the general steps of creating work breakdown structures in Microsoft Project 2019, the general concepts and theory behind these steps are the same, regardless of which software solution is used. Therefore, to keep this article as open as possible, the guide was written as generally as possible without focusing on a single tool.