Work Breakdown Structure (WBS)

A Work Breakdown Structure is a hierarchical decomposition of the total scope of work. It’s the foundation for planning, estimating, scheduling, and controlling a project.

What is a WBS?

The WBS:

• Defines 100% of the project scope
• Organises work into manageable sections
• Provides the basis for estimating and scheduling
• Enables clear assignment of responsibility
• Facilitates progress tracking and reporting

WBS Structure

Terminology

The 100% Rule

The most important WBS principle:

The WBS must include 100% of the work defined by the project scope and capture all deliverables - internal, external, and interim.

This means:

• No work outside the WBS
• No gaps in coverage
• Child elements sum to parent
• If it’s not in the WBS, it’s not in scope

Creating a WBS

Top-Down Approach

Start with major deliverables and decompose downward:

1. Identify major deliverables from scope statement
2. Decompose each deliverable into smaller components
3. Continue decomposing until work packages are reached
4. Verify 100% rule at each level
5. Assign WBS codes for tracking

Bottom-Up Approach

Start with detailed tasks and group upward:

1. Brainstorm all tasks needed
2. Group related tasks into work packages
3. Group work packages into deliverables
4. Verify completeness against scope
5. Assign WBS codes

Decomposition Guidelines

Stop decomposing when the work package:

• Can be estimated with confidence
• Can be scheduled with start/end dates
• Can be assigned to one person or team
• Can be tracked for progress
• Takes 8-80 hours (common guideline)

WBS Formats

Hierarchical Chart

1.0 Website Redesign
├── 1.1 Project Management
│   ├── 1.1.1 Planning
│   ├── 1.1.2 Monitoring
│   └── 1.1.3 Closure
├── 1.2 Design
│   ├── 1.2.1 Wireframes
│   ├── 1.2.2 Visual Design
│   └── 1.2.3 Prototypes
├── 1.3 Development
│   ├── 1.3.1 Front-end
│   ├── 1.3.2 Back-end
│   └── 1.3.3 Integration
└── 1.4 Testing & Launch
    ├── 1.4.1 Testing
    ├── 1.4.2 UAT
    └── 1.4.3 Deployment

Tabular Format

WBS Dictionary

The WBS Dictionary provides detailed information about each WBS element:

Deliverable vs Activity-Based WBS

Deliverable-Based (Recommended)

Organised around outputs and results:

1.0 New Product Launch
├── 1.1 Product
│   ├── 1.1.1 Prototype
│   └── 1.1.2 Final Product
├── 1.2 Documentation
│   ├── 1.2.1 User Manual
│   └── 1.2.2 Training Materials
└── 1.3 Marketing Collateral
    ├── 1.3.1 Brochures
    └── 1.3.2 Website Content

Pros: Focus on outcomes, easier stakeholder communication

Activity-Based

Organised around phases or work types:

1.0 New Product Launch
├── 1.1 Planning
├── 1.2 Design
├── 1.3 Development
├── 1.4 Testing
└── 1.5 Deployment

Pros: Familiar to project teams, aligns with lifecycle

Product Breakdown Structure (PBS)

A PBS focuses purely on products/deliverables without activities:

PBS vs WBS

In PRINCE2, you typically create the PBS first, then derive the WBS from it.

WBS Numbering (Coding)

A consistent numbering scheme enables tracking and reporting:

Decimal System

1.0     Level 1
1.1     Level 2
1.1.1   Level 3
1.1.1.1 Level 4

Guidelines

• Unique codes - Each element has one code
• Hierarchical - Code shows position in structure
• Consistent depth - Similar items at same level
• Room to grow - Allow for additions (e.g., 1.1, 1.2, 1.3… not 1.1, 1.2, 1.21)

Common WBS Mistakes

1. Not Including All Work

Problem: Management, QA, or transition work omitted Solution: Include PM, testing, training, and handover activities

2. Too Many Levels

Problem: Overly detailed, hard to manage Solution: Stop at work packages (8-80 hours)

3. Activity Lists, Not Structure

Problem: Flat list of tasks without hierarchy Solution: Group into logical deliverables

4. Skipping Work Packages

Problem: Vague elements that can’t be estimated Solution: Decompose until assignable and measurable

5. Scope Creep via WBS

Problem: New items added without change control Solution: WBS changes follow scope change process

WBS for Agile Projects

In Agile, the WBS equivalent is often:

The Product Backlog serves as a living, prioritised WBS.

WBS Creation Checklist

• Scope statement reviewed and understood?
• Major deliverables identified?
• All work included (100% rule)?
• Work packages estimable and assignable?
• Consistent level of detail?
• WBS codes assigned?
• Dictionary entries created?
• Stakeholders reviewed and approved?
• Baselined for change control?

Worked Example

Project: Office Relocation

1.0 Office Relocation
├── 1.1 Project Management
│   ├── 1.1.1 Project Planning
│   ├── 1.1.2 Stakeholder Communication
│   └── 1.1.3 Project Closure
├── 1.2 New Office Setup
│   ├── 1.2.1 Lease Negotiation
│   ├── 1.2.2 Fit-out Works
│   ├── 1.2.3 IT Infrastructure
│   └── 1.2.4 Furniture Installation
├── 1.3 Transition
│   ├── 1.3.1 Packing
│   ├── 1.3.2 Physical Move
│   └── 1.3.3 Unpacking
└── 1.4 Old Office Closure
    ├── 1.4.1 Cleaning
    ├── 1.4.2 Repairs
    └── 1.4.3 Lease Termination

Related Resources

• Estimation Techniques - Estimating work packages
• Critical Path Method - Scheduling WBS elements
• Gantt Charts - Visualising the schedule
• Deliverables / WBS / PBS - Template download
• PRINCE2 Plans Theme - PBS in PRINCE2