Class 108: Work Breakdown Structures

September 23, 2021 0 Comments


A Work Breakdown Structure, commonly abbreviated to WBS, organizes a construction schedule by grouping together activities based on similar trade or physical location in an expandable outline format. A well-organized WBS enables an efficient review of a construction schedule. AACE defines a WBS as a “systematic approach to reflect a top-down product-oriented hierarchy structure with each lower level providing more detail and smaller elements of the overall work.”1

Example of a WBS:

The example above shows a construction schedule for a high-end mixed-use skyscraper.  All activities are organized in a multi-level WBS. The project is first organized by phase (owner milestones, pre-construction, etc.) and then by trade (electrical, plumbing, etc.). For example, to review the work remaining to “Bid and Award” the “Plumbing” scope of work, simply locate this section in the WBS and review the required work and its associated dates and logic. Without a succinct WBS, searching through thousands of activities in a schedule or trying to locate specific trades would be an inefficient process. 

Why is a WBS important?

A WBS becomes more important as schedules complexity increases.  A project can have multiple areas or phases, each with its own activities and milestones tied to contractual obligations. Breaking out the phases of work before and during construction helps organize the project and define responsibility for different tasks. Using a consistent WBS can also help non-project personnel quickly understand the status of the project without having to understand the intricacies of the schedule.

WBS Summary:

1.      Work Breakdown Structures help keep construction schedules organized and manageable.

2.      Work Breakdown Structures reflect a top-down product-oriented hierarchy structure with each lower level providing more detail.

Key Terms:

Work Breakdown Structure (WBS) - grouping of activities within a construction schedule based on similar trade or physical location

Construction Schedule - a comprehensive and realistic plan that represents the specific activities, reasonable duration for the activities, and the planned sequence of work for the project

Logic - Relationship describing the interdependency of starts and finishes between    activities or events


1.      AACE International Recommended Practice.  10S-90: Cost Engineering Terminology.