Deliverable-based WBS
Deliverable-based work breakdown structures start with the larger end goal at the top of the chart (such as building a house). Beneath the larger end goal are individual components/categories (such as foundation, interior, and exterior). Under each of those is a list of deliverables that need to be done in order for the individual components/categories–and eventually, the larger end goal–to be considered complete (such as masonry and landscaping under the “exterior” category, or plumbing, electrical, and finish carpentry under the “interior” category). On each of these tiers, the project manager will specify the amount of time allocated to complete each deliverable along with its share of the project budget. The main benefit of a deliverable-based work breakdown structure is that it is much less prescriptive for project teams to follow. It allows them relative flexibility when it comes to determining how best to approach the work. With budget and scope spelled out, teams are free to work as they please within the constraints as long as the work is done by the deadline.
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Benefits of a deliverable-based WBS
Because a deliverable-based WBS breaks projects down into individual outcomes that need to be completed, it helps project managers handle a project’s scope and avoid scope creep. Deliverable-based work breakdown structures are much less broad than phase-based work breakdown structures, which makes it easier for all stakeholders to know exactly what they need to do and focus exclusively on it. Everyone on the team can be held accountable for their contributions, so there’s a lot more cohesion required to finish the project properly. Deliverable-based work breakdown structures become much more valuable as a project becomes more complex. This is because resource allocation becomes much more precise and project managers are able to tailor a project’s budget exactly to each deliverable’s requirements. There is a clear focus on end results when deliverable-based work breakdown structures are used, which can help encourage quality assurance. The goals of each deliverable are made much clearer, and thus there is a very cut-and-dry definition of success.
Phase-based WBS
Phase-based work breakdown structures, as the name suggests, categorize projects into their unique “phases”. Using the housebuilding example from before, the second-tier deliverables would be broken down into design, procurement, construction, inspections, and final hand-off. Just like deliverable-based work breakdown structures, specific tasks are placed under each of these. The major difference between this approach and the deliverable-based approach is that the second-tier tasks need to be completed in the order they are broken down into (for example, you can not start on plumbing–which is in the second phase–before the permits and design work from the first phase are completed). This approach is particularly helpful when working on projects with tight time demands, because you cannot start on the next round of work until the previous round is completed.
Benefits of a phase-based WBS
Project managers tend to use phase-based work breakdown structures when a project’s life cycle is either accelerated or very drawn out. While deliverable-based work breakdown structures can feature a number of tasks that can be completed simultaneously, objectives in a phase-based work breakdown structure must generally be completed sequentially. Because of this, stakeholders generally aren’t left standing around waiting for their jobs to begin. They can spend the time planning, staffing, and doing whatever else they need to do before commencing work. The general public also tends to understand phase-based work breakdown structures more easily (even if most can’t put the technical name to it), so project teams building infrastructure or public works, or developers soliciting input from community members often use them in public-facing documents.
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When not to use a WBS
Even though they may seem like cure-alls for project planning and delivery, there a number of scenarios when work breakdown structures are unnecessary or unneeded. On smaller, more simple projects with fewer stakeholders, work breakdown structures can introduce a level of complexity or triviality that can slow things down. If you are working directly with the people performing the work (for example, if you hire your own team of construction labourers instead of using a general contractor), they may not be used to work breakdown structures, which adds the task of training them on its use to the rest of your project. You also should not rely on work breakdown structures for highly variable projects where you can rely on components changing as you work.
Emergency or very time-limited projects are not good candidates for the use of work breakdown structures. If you need to get to work right away and complete the work in an extremely short period of time, the creation and implementation of a work breakdown structure is inappropriate and takes away from whatever scarce time you have to complete the project. You should also take into account who you are working with before spending time on a work breakdown structure. Many higher-level stakeholders may not be interested in the granularity of a work breakdown structure and view it as added complication. Conversely, you might be working with highly detail-oriented people who will receive it much better. You should not assume that two project teams prefer working the same way.
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The 100% rule
If you decide to implement a work breakdown structure, whether deliverable- or phase-based, keep in mind something called “the 100% rule”. This basically means that every “level” of the work breakdown structure accounts for 100% of the work. If the project is to build a house, “build a house” is on its own level and represents 100% of the job. Beneath “build a house” is where you’ll find the second-level tasks, such as foundation, electrical, plumbing, etc., which taken together represent 100% of the job. Beneath all of these second-level tasks is where the more specific and granular sub-tasks live, and taken together, they all represent 100% of the job. It is absolutely crucial that every “level” of the structure encompasses 100% of the work because anything left off will be forgotten about or unaccounted for, which can ruin budgets and schedules. Following this rule makes sure that your planning is as thorough as possible, and that your project will truly be completed.
Work breakdown structures may seem complicated to the uninitiated, but they are valuable tools when it comes to planning projects and delineating responsibility among your team. Even if you have dedicated project management staff on your team, you should familiarize yourself with how to properly use and read work breakdown structures. It will make you a more efficient team member, while helping everyone else stay on the same page.
