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Overview

Image of the words Work Breakdown Structure in red ink.

A Work Breakdown Structure (WBS) is used to make complex projects more manageable. It is designed to help break down a project into manageable chunks that can be effectively estimated and supervised.

Some widely used reasons for creating a WBS include:

  • Assists with accurate project organization

  • Helps with assigning responsibilities

  • Shows the control points and project milestones

  • Allows for more accurate estimation of cost, risk, and time

  • Helps explain the project scope to stakeholders

Some people create tables or lists for their WBS, but most use graphics or charts. The two primary types of graphics or charts are Gantt charts and PERT/CPM charts. Both types of charts insure that you do not fall behind on the project, however PERT/CPM prevents you from setting an impossible schedule. PERT/CPM charts are more useful for scheduling, monitoring, and controlling the actual work. We will illustrate WBS using a PERT/CPM chart.

To start constructing a WBS, the project manager and subject matter experts determine the main deliverables for the project. They then start decomposing these deliverables, breaking them down to successively smaller chunks of work. You may ask, “How small?”.

Size of work chunks varies by project, management style, and company, but some predetermined rule should govern the size and scope of the smallest chunks of work. Some rule examples include:

  • Two week rule – nothing is broken down smaller than it would take two weeks to complete.

  • 8/80 rule – no chunk would take less than 8 hours or longer than 80 hours to complete.

  • One day rule – nothing is broken down smaller than it would take to complete in one day.

We will use the One Day Rule for our WBS using a PERT/CPM chart.