Work Breakdown Structure: Decomposition by Phase and Deliverable

PMBOK v8 Definition

The Work Breakdown Structure (WBS) 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. PMBOK v8 illustrates two primary organization approaches: a WBS organized by phase (Figure 5-7) showing project lifecycle stages as Level 2 elements, and a WBS organized by major deliverables (Figure 5-8) showing tangible outputs as Level 2 elements. The WBS decomposes down through work packages (Figure 5-6), which are the lowest level of WBS components where cost and duration can be estimated and managed.

Why It Matters for the Exam

The WBS is a foundational scope management tool tested in approximately 8-12% of PMI exam questions. Questions frequently appear in scenarios asking you to identify the correct decomposition approach, recognize the WBS as the primary input for scope baseline creation, and distinguish between WBS organized by phase versus by deliverable. Expect situational questions where you must select the appropriate WBS structure for a given project type.

Key Points to Remember (for the exam)

• Primary Purpose: Decomposes total project scope into manageable work packages for planning, executing, monitoring, and controlling
• Two Organization Approaches: Phase-based (Figure 5-7) for sequential lifecycle projects OR deliverable-based (Figure 5-8) for product-oriented projects
• Decomposition Level: Work packages (Figure 5-6) are the lowest WBS level – NOT activities or tasks
• Critical Rule: 100% Rule – The WBS must capture 100% of the scope defined in the project scope statement
• Common Confusion: WBS is NOT a list of activities; it shows deliverables and work packages, not the sequence of work
• Key Output: The WBS, WBS dictionary, and scope statement together form the scope baseline
• Verification Tool: The WBS is verified against the project scope statement to ensure complete coverage

Typical PMI Exam Example

A construction project manager is creating the WBS for a new office building. The project has four phases: Design, Procurement, Construction, and Commissioning. The PM should organize the WBS by phase (Figure 5-7), placing each phase as Level 2, then decompose each phase into major deliverables like "Foundation Plans" under Design and "Steel Structure" under Construction.

PMI Exam Traps

• Trap: Confusing WBS decomposition with activity sequencing

• Reality: WBS shows "what" (deliverables and work packages), not "when" (schedule) or "how" (activities)

• Trap: Thinking the WBS must show phases AND deliverables simultaneously at Level 2

• Reality: Choose ONE organization approach – either phase-based OR deliverable-based, not both at the same level

• Trap: Including activities or tasks as WBS elements

• Reality: WBS stops at work packages; activities are defined later during schedule development

• Trap: Believing the WBS must be decomposed to the same level for all branches

• Reality: Different branches may decompose to different levels based on management needs and risk

Important PMI Connections

Quick Review Questions

1. A project has five phases: Initiation, Planning, Execution, Monitoring, and Closeout. Which WBS organization approach (Figure 5-7 or Figure 5-8) is most appropriate?

2. What is the lowest level of the WBS where cost and duration can be estimated?

3. True or False: The WBS should include all activities required to complete the project deliverables.

4. A project manager has a WBS with Level 2 elements: "Foundation," "Walls," "Roof," "Electrical," and "Plumbing." Is this organized by phase or by major deliverables?

5. What three documents together form the scope baseline?

PMBOK v8 Reference

Section 5.4 – Create WBS (Figures 5-6, 5-7, and 5-8: Sample WBS Decomposed Down Through Work Packages, Sample WBS Organized by Phase, Sample WBS With Major Deliverables)