---
title: "Principles for creating WBS"
subject: "ICT Project Management"
chapter: 7
key: "semester_7/ict_project_management:wbs-principles"
source: https://www.bctengineer.com/q/semester_7/ict_project_management/wbs-principles
site: BCT Engineering
---

# Principles for creating WBS

ICT Project Management · Chapter 7: Project Integration Management

- Asked in: year not given
- Video: [Project Management: What is a Work Breakdown Structure?](https://www.youtube.com/watch?v=wEWhnodF6ig) — ProjectManager
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/ict_project_management/wbs-principles
- Whole chapter: https://www.bctengineer.com/md/semester_7/ict_project_management/chapter-7

## Question

What are the basic principles for creating WBSs?

## Short answer

WBS must follow the 100% rule, be deliverable-oriented, mutually exclusive, and decomposed to work packages of 8-80 hours. Each package should have a single owner, and all necessary work including management is included. Use team input and a WBS dictionary.

## Answer

A WBS must be built with sound principles so that it fully and clearly represents the project scope. The basic principles are as follows.

1. **100% rule**: the WBS must include 100% of the work defined by the project scope and capture all deliverables, including project management. The sum of the work at the child level must equal 100% of the work of the parent. Nothing outside the WBS is part of the project.
2. **Deliverable-oriented**: elements should be products, results or services (nouns), not actions only. Example: "Design document" rather than "design".
3. **Mutually exclusive elements**: no overlap in scope between elements, which avoids duplicated work and cost and ambiguity of responsibility.
4. **Hierarchical decomposition**: break down level by level from the project down to work packages, and each level is more detailed.
5. **Level of detail**: decompose until the work package can be reliably estimated, assigned to a person and managed. A rule of thumb is 8-80 hours (the "8/80 rule") or one reporting period.
6. **Single responsibility**: each work package should be assigned to one responsible unit or person.
7. **Appropriate number of levels**: usually 3 to 6; too few means vague, too many means micromanagement.
8. **Include everything necessary**: project management, quality, procurement and training work, not only technical work.
9. **Involve the team**: people who will do the work should help to create the WBS, which improves accuracy and commitment.
10. **Use templates and past WBSs** from similar projects.
11. **Consistent organisation**: choose a clear basis (by phase, product component or function) and apply consistently.
12. **WBS dictionary** to define each element.
13. **Keep updated** through change control.
14. **Progressive elaboration**: later phases can be left at a higher level until more is known (rolling wave planning).

| Principle | Check |
|---|---|
| 100% rule | Nothing missing |
| Mutually exclusive | No overlap |
| Work package size | Estimable, assignable |
| Deliverable focus | Noun-based names |

**Example:** In a software project, "Testing" is divided into Unit test plan, System test report and UAT sign-off, each owned by the QA lead.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Why should WBS elements be mutually exclusive?
   A. To allow several people to own one package
   B. So that the WBS has fewer levels
   C. To avoid overlap that causes duplicated work and cost and unclear responsibility
   D. So that all elements take the same time
   Answer: C. Overlap in scope between elements duplicates work and cost and confuses who is responsible. (Key point: Mutually exclusive elements)

2. How far should the decomposition continue?
   A. Until the cost of each item is equal
   B. Until the work package can be reliably estimated, assigned and managed (e.g. 8-80 hours)
   C. Until every task is under one hour
   D. Only to the second level
   Answer: B. Decompose until the work package is estimable and manageable; the 8/80 rule or one reporting period is the rule of thumb. (Key point: Level of detail)

3. What is the problem if a WBS has too many levels?
   A. It removes the need for a dictionary
   B. It leads to micromanagement
   C. It breaks the 100% rule
   D. It makes the WBS non-deliverable-oriented
   Answer: B. Too few levels is vague and too many means micromanagement, so 3 to 6 are used. (Key point: Number of levels)

4. What does progressive elaboration (rolling wave) allow in a WBS?
   A. Skipping project management work
   B. Assigning one package to many owners
   C. Removing the WBS dictionary
   D. Leaving later phases at a higher level until more is known
   Answer: D. Later-phase work can stay at a higher level and be detailed when more information is available. (Key point: Progressive elaboration)

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