WBS Structure

The WBS provides a structured framework for estimating, budgeting, scheduling, measuring, and reporting the status and performance of the project in an integrated manner, thus making progress reporting meaningful. The structure also facilitates delegation of authority to lower level managers, which allows the project manager to manage the overall project while ensuring that the details also receive the appropriate level of attention.

When properly developed, the WBS and corresponding WBS dictionary help ensure that the project scope is accounted for and assigned to a responsible individual. A properly created WBS also serves as a summary-level checklist for general activities that must be completed to meet contractual requirements. As such, it is a helpful tool to create the project schedule and EV metrics, although these will eventually be developed at a lower level of detail. The WBS provides a roadmap to plan the project. A poorly designed roadmap inevitably causes problems. The project team must understand that a well-designed WBS:

  • Reflects the way work will be performed, including the subcontracting strategy
  • Provides information and structure to report progress and financial status to the client
  • Helps focus management on critical aspects of the project (i.e., it is risk-based)
  • Does not create an unusual administrative burden (i.e., it is practical)
  • Aligns with the job cost structure in PRISM (i.e., unique PRISM WBS numbers for the lowest level of the WBS)

A plan is required for the successful accomplishment of both contract and corporate objectives. It needs to define all effort to be expended, assigns responsibility to a specially identified organizational element, and establishes schedules and budgets for the accomplishment of work. The foremost step in the planning process after project requirements definition is the Work Breakdown Structure (WBS).

The Work Breakdown Structure breaks down the work into smaller elements, thus providing a greater probability that every major and minor activity will be accounted for. It is structured in accordance with the way the work will be performed and reflects the way in which project costs and data will be summarized and eventually reported.

The Work Breakdown Structure provides a common framework from which:  

  • The total program can be described as a summation of subdivided elements.
  • Planning can be performed
  • Costs and budgets can be established
  • Time, cost and performance can be tracked
  • Objectives can be linked to company resources in a logical manner
  • Schedules and status-reporting procedures can be established
  • Network construction and control planning can be initiated.
  • The responsibility assignments for each element can be established

Preparation of the Work Breakdown Structure also considers other areas that require structured data, such as scheduling, configuration management, contract funding, and technical performance parameters.

Work Breakdown Structure may also act as a communications tool, providing detailed information to different levels of management. 

DEVELOPING THE WBS

The first step in developing a WBS is to identify the scope of the project—what must be delivered to achieve project success. A thorough review and understanding of project scope documents is required to ensure consistency among the WBS, project requirements, and client reporting requirements.

The project planner works with the project technical team to define major project phases and deliverables. Deliverables are typically thought of in terms of tangible products, such as drawings or construction of a building. The “deliverable” must be well defined, able to be measured or verified, and complete a part of—or the entire—project. Phases of work, such as design or construction, can also represent major project “deliverables” when developing a WBS.

The third step in developing the WBS is to break the major phases/deliverables into successive levels of detail. In this step, the work is broken down to levels of detail consistent with requirements for scheduling and determining EV. For each major phase/deliverable, the need for further breakdown is evaluated. The process is repeated with successive levels of detail created (continuing the hierarchical structure) until the detail is such that the project can be estimated, scheduled, and objectively measured.

Each branch is independent, and all do not require the same level of detail. The level of detail depends on the nature of work in each element and the associated risks, which is often a function of the subcontracting strategy and subcontract types. After the scope of work has been fully deconstructed to the most detailed levels, appropriate reporting levels are determined. For each branch in the WBS, identify the level at which actual costs should be collected and compared to budgets and project progress to generate forecasts, analyze variances and produce client reports.

Remember that different levels of detail are generally required for each branch. The level at which costs will be collected and reported becomes the work package level, which, by definition, is the lowest level of the formal WBS. Subelements at a level of detail below the work packages are used to schedule, budget, and measure the work in a manner that allows for the meaningful summarization of information at the work package level.

WBS development is an iterative process; the next development step is a coordinated review and refinement of the WBS, budget, and schedule until project stakeholders agree that the project can be planned successfully and that execution and control will produce the desired outcomes. This refinement will occur primarily during the planning phase but can also occur during project execution.

Be sure to include responsible team members and appropriate client personnel in the review and development process. Although the development of the WBS is a flexible and iterative process, once the customer and stakeholders approve it, the project team must apply a rigorous change control process to document and manage changes.

The WBS should be revised only when work scope changes are approved through a formal change order. This is the final step in developing the WBS.

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